a r X i v :a s t r o -p h /0306167v 1 9 J u n 2003
Astronomy &Astrophysics manuscript no.(will be inserted by hand later)
Spectroscopic and photometric studies of low-metallicity
star-forming dwarf galaxies.III.SBS 1415+437
N.G.Guseva 1,P.Papaderos 2,Y.I.Izotov 1,R.F.Green 3,K.J.Fricke 2,T.X.Thuan 4,and K.G.Noeske 2
1Main Astronomical Observatory,Ukrainian National Academy of Sciences,Zabolotnoho 27,Kyiv 03680,Ukraine 2Universit¨a ts–Sternwarte,Geismarlandstra?e 11,D–37083G¨o ttingen,Germany 3National Optical Astronomy Observatory,Tucson,AZ 85726,USA
4
Astronomy Department,University of Virginia,Charlottesville,VA 22903,USA
Received
;Accepted
Abstract.We present a detailed optical spectroscopic and B ,V ,I ,H αphotometric study of the metal-de?cient cometary blue compact dwarf (BCD)galaxy SBS 1415+437.We derive an oxygen abundance 12+log(O/H)=7.61±0.01and 7.62±0.03(Z =Z ⊙/20)?in the two brightest H ii regions,among the lowest in BCDs.The helium mass fractions in these regions are Y =0.246±0.003and 0.243±0.010.Four techniques based on the equivalent widths of the hydrogen emission and absorption lines,the spectral energy distribution and the colours of the galaxy are used to put constraints on the age of the stellar population in the low-surface-brightness (LSB)component of the galaxy,assuming two limiting cases of star formation (SF),the case of an instantaneous burst and that of a continuous SF with a constant or a variable star formation rate (SFR).The spectroscopic and photometric data for di?erent regions of the LSB component are well reproduced by a young stellar population with an age t ≤250Myr,assuming a small extinction in the range A V =0–0.6mag.Assuming no extinction,we ?nd that the upper limit for the mass of the old stellar population,formed between 2.5Gyr and 10Gyr,is not greater than ～(1/20–1)of that of the stellar population formed during the last ～250Myr.Depending on the region considered,this also implies that the SFR in the most recent SF period must be 20to 1000times greater than the SFR at ages >～2.5Gyr.We compare the photometric and spectroscopic properties of SBS 1415+437with those of a sample of 26low-metallicity dwarf irregular and BCD galaxies.We show that there is a clear trend for the stellar LSB component of lower-metallicity galaxies to be bluer.This trend cannot be explained only by metallicity e?ects.There must be also a change in the age of the stellar populations.The most metal-de?cient galaxies have also smaller luminosity-weighted ages.
Key words.galaxies:abundances —galaxies:dwarf —galaxies:evolution —galaxies:compact —galaxies:starburst —galaxies:stellar content —galaxies:individual (SBS 1415+437)
1.Introduction
Since its discovery as a metal-de?cient blue compact dwarf (BCD)galaxy (Thuan,Izotov &Lipovetsky 1995),SBS 1415+437(≡CG 389)has been considered as a probable nearby young dwarf galaxy.Situated at a distance D =11.4Mpc it was classi?ed by Thuan,Izotov &Foltz (1999)as a cometary BCD with a very bright supergiant H ii region at the SW tip of the galaxy.
From 4m Kitt Peak National Observatory (KPNO)telescope spectra,Thuan et al.(1995)?rst derived an oxygen abundance of 12+log(O/H)=7.51±0.01in SBS 1415+437placing the galaxy among the most metal-de?cient BCDs https://www.doczj.com/doc/418459571.html,ter,Izotov &Thuan (1998,1999)derived from the same spectrum 12+log(O/H)=
2N.G.Guseva et al.
spectral energy distributions(SED)in the optical range,
they concluded that SBS1415+437is a truly young galaxy
that did not start to form stars until～100Myr ago.
However,the V and I images used by Thuan et al.(1999)
were not deep enough for the detection of old red giant
branch(RGB)stars in the CMD.Furthermore,they con-
sidered an instantaneous burst model which gives only a
lower limit to the age of the stellar population in SBS
1415+437.
In this paper we combine new spectroscopic and photo-
metric data with previous observations to derive elemental
abundances and to better constrain the age of the stellar
population in SBS1415+437.For the latter task we use
four di?erent techniques of age determination and con-
sider di?erent star formation(SF)histories.The paper
is organized as follows.In Sect.2we describe the obser-
vations and data reduction.The photometric properties
of SBS1415+437are described in Sect.3.We derive in
Sect.4the chemical abundances in the two brightest H ii
regions.In Sect.5we discuss the properties of the stel-
lar populations in SBS1415+437and compare them with
those in other low-metallicity dwarf galaxies.Finally,Sect.
6summarises the main conclusions of this study.
2.Observations and data reduction
2.1.Photometry
Narrow-band images of SBS1415+437in the Hαline at
λ6563?A through a passband with a full width at half max-
imum(FWHM)of74?A,and in the adjacent continuum at
λ6477?A through a passband with FWHM=72?A were
obtained with the Kitt Peak12.1m telescope on April
22,1999during a photometric night.The telescope was
equipped with a Tektronix1024×1024CCD detector
operating at a gain of3e?ADU?1,giving an instrumen-
tal scale of0.′′305pixel?1and?eld of view of5′.The total
exposures of50min in the Hαline and40min in the adja-
cent continuum bluewards of Hαwere split up into5and4
subexposures,slightly o?set with respect to each other for
removal of cosmic particle hits and bad pixels.The point
spread function has a FWHM of2.′′2.Bias and?at–?eld
frames were obtained during the same night.The standard
stars Feige34and HZ44were observed in both?lters dur-
ing the same night at several airmasses for absolute?ux
calibration.
Another broad-band B image(15min)of SBS
1415+437was obtained on March9,1997under pho-
tometric conditions,with the CAFOS focal reducer at-
tached to the 2.2m telescope of the German-Spanish
Astronomical Center,Calar Alto2,Spain.CAFOS was
3IRAF is the Image Reduction and Analysis Facility dis-
tributed by the National Optical Astronomy Observatory,
which is operated by the AURA under cooperative agreement
with the NSF.
4Munich Image Data Analysis System,provided by the
European Southern Observatory(ESO).
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS 1415+437
3
Fig.2.Continuum-subtracted H αimage of SBS 1415+437with superposed H αcontinuum isophotes.Regions with nebular emission are labeled e 1,e 2and e 4.The faint region e 3with H βand H αemission lines in its spectrum is not seen in the H αimage.
CCD detector.The 2′′×300′′
slit was centered on the brightest H ii region e 1(slit 2in Fig.1)with position angle P.A.=48?so as to include the second brightest H ii region e 2to the SW of region e 1.We used the KPC-10A grating in ?rst order and a GG 375order separation ?lter.The spatial scale along the slit was 0.′′69pixel ?1and the spec-tral resolution ～7?A (FWHM).The spectra were obtained at an airmass 1.27.The total exposure time of 60minutes was broken up into 3subexposures.No correction for at-mospheric refraction was made because of the small air-mass during the observations.Two Kitt Peak spectropho-tometric standard stars were observed for ?ux calibration.For wavelength calibration,He-Ne-Ar comparison spectra were obtained after each exposure.
The data reduction was performed with the IRAF software package.This includes bias–subtraction,?at–?eld correction,cosmic-ray removal,wavelength calibra-tion,night sky background subtraction,correction for at-mospheric extinction and absolute ?ux calibration of the two–dimensional spectrum.
For abundance determination,one-dimensional spec-tra of regions e 1and e 2were extracted within apertures of 2′′×4.′′6and 2′′×4.′′0,respectively.In addition,we extracted spectra of the low-surface-brightness (LSB)re-
Fig.3.(a )Surface brightness pro?les (SBPs)of SBS 1415+437in V and I (?lled and open circles,respectively),derived from HST /WFPC2data.A linear ?t to the V
SBP in the radius interval 4′′≤R ?<～13′′
is shown by the upper solid-grey line.Both SBPs reveal a signi?cant slope
change for R ?>～13′′
.Filled squares show the ground-based B SBP,shifted vertically by 0.5mag.In addition to the
exponential intensity slope at radii 4′′≤R ?<～13′′
,this
pro?le reveals for R ?>～16′′
an outer exponential regime with an α～0.27kpc (lower solid-grey line).The residu-als after subtraction of the outer exponential distribution from the B SBP are shown by crosses.(b )(V ?I )colour pro?le of SBS 1415+437,computed from subtraction of the SBPs in (a ).A strong colour gradient γ+=2.5mag kpc ?1is derived for radii smaller than the e?ective radius r e?(inner ?t).The (V ?I )colour of 0.4–0.5mag for larger radii is nearly constant with a γ+<0.2mag kpc ?https://www.doczj.com/doc/418459571.html,parison of the B and V SBPs implies a B ?V color ～0.2mag in the radius range 13′′≤R ?≤16′′.
gions a 3and a 4with strong hydrogen Balmer absorption lines,and of region e 3with H αand H βin emission (Fig.1).
We also used the two-dimensional MMT spectrum ob-tained by Thuan et al.(1999)with the slit oriented at P.A.=22?(slit 1in Fig.1).We extracted one-dimensional spectra of the LSB regions a 1and a 2within apertures of 1.′′5×3.′′4and 1.′′5×13.′′2,respectively (Fig.1).These spectra show strong hydrogen Balmer absorption lines.
4N.G.Guseva et
al.
Fig.4.The KPNO4m telescope spectra of the brightest H ii regions e1and e2with the identi?ed emission lines.The lower spectra in(a)and(b)are the observed spectra downscaled by factors of50and30,respectively.
The selected LSB regions are listed in Tables3and4
with their positions and spatial extents.Origins are set
at the center of the brightest region e1(Fig.1,2).The
spectra of the LSB regions are used to study the stellar
populations and to constrain the age of the oldest stars
which contribute to the light of these regions.
3.Photometric properties
It is seen from the continuum-subtracted Hαimages(Fig.
2)that star-forming activity in SBS1415+437is primarily
occurring in regions e1and e2,with some additional faint
Hαemission present in region e4.However,the available
narrow-band data are not deep enough for tracing faint
Hαemission in other regions of the LSB component,such
as in regions a1,a3and e3where Hαand Hβhave been
detected spectroscopically(Table3).The latter fact sug-
gests that some low-level SF may be present at various
locations within the LSB component.
The photometric properties of the stellar LSB compo-
nent of SBS1415+437were?rst investigated by Thuan
et al.(1999)using HST/WFPC2V and I images.These
authors?t the surface brightness pro?les(SBPs)of SBS
1415+437with an exponential distribution in the radius
range4′′≤R?<～13′′with a scale lengthα=5.′′4(≈0.3
kpc).However,their study was limited by the fact that
the HST images do not include the outermost NE part of
the LSB component.Furthermore,the SBPs in Thuan et
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS1415+4375 al.(1999)reach only a surface brightness levelμ～24.5
mag arcsec?2.It is known,however,that the star-forming
component may contribute to the optical BCD emission
to fainter surface brightness levels(see e.g.Papaderos et
al.2002and references therein).A comparatively young
stellar population has been observed in the inner part of
the LSB component of other cometary BCDs,several hun-
dred pc away from the brightest H ii region(Noeske et al.
2000;Guseva et al.2001;Fricke et al.2001).Therefore
deeper images are needed to study the outer parts of the
LSB component in SBS1415+437.
Note that the SBPs by Thuan et al.(1999)show in
the outermost part(13′′<～R?<～16′′,or24<～μV<～24.5)
a steeper exponential intensity decrease than the one ob-
served at intermediate intensity levels.This slope change,
not discussed in Thuan et al.(1999),is found indepen-
dently by us in the HST/WFPC2SBPs derived with the
method iv of Papaderos et al.(2002)and ellipse?tting
to the visible part of the LSB component.While the lat-
ter method extends surface photometry out to larger radii
(R?～22′′),it is subject to large uncertainties because
the NE part of the LSB component withμ>～24.5V mag
arcsec?2(R?>～16′′)lies outside the HST/WFPC2?eld of view.Additionally,the outermost LSB isophotes show considerable deviations from ellipticity.
To study the surface brightness distribution at large radii we use the ground-based Calar Alto B image.Despite the poor spatial resolution this image allows us to study the entire LSB component out to its Holmberg radius.The change in the exponential slope for13′′<～R?<～16′′is con-?rmed from the ground-based B SBP.At large radii,how-ever,this SBP reveals a?atter,outer exponential regime with a scale lengthαfairly comparable to that previously obtained at intermediate intensity levels from HST data (upper thick-grey line in Fig.3a).From?tting an expo-nential model to the B SBP for R?≥16′′(lower thick-grey line in Fig.3a)we obtain a central surface brightness μE,0=21.37B mag arcsec?2and a scale lengthα=0.27 kpc.
Note,however,that the inner exponential pro?le stud-ied by Thuan et al.(1999)is>～0.3mag brighter than the outer one,which suggests that more than1/4of the emis-sion associated with this pro?le originates from the part of the LSB component between regions e1and a2.
The present data provide no compelling evidence for a large age di?erence between the stellar population which dominates within the inner exponential regime discussed in Thuan et al.(1999)and that responsible for the outer-most LSB emission(i.e.for R?>16′′).The(V?I)pro?le reveals a strong
colour gradient(γ+=2.5mag kpc?1;inner solid-grey line in Fig.3b)within the inner5′′,or roughly the V band e?ective radius(r e?=5.′′6)of SBS1415+437. At larger radii,however,linear?ts to the(V?I)pro-?le yield,depending on whether they are error-weighted or not,a gradient not exceeding0.1and0.2mag kpc?1, https://www.doczj.com/doc/418459571.html,parable values are also found from sub-traction of the exponential?ts in V and I(Fig.3a)in the radius range r e?≤R?≤13′′(Fig.3b,solid-grey line at intermediate radii).
4.Chemical abundances
In this section we derive the elemental abundances of re-gions e1and e2using the Kitt Peak4m telescope observa-tions.Their spectra with strong emission lines are shown in Fig.4.
The observed(F(λ))and extinction-corrected(I(λ)) emission line?uxes relative to the Hβemission line?uxes, their equivalent widths EW,the extinction coe?cients C(Hβ),the observed?uxes of the Hβemission line,and the equivalent widths of the hydrogen absorption lines for regions e1and e2are shown in Table1.Despite the dif-ferences in aperture(2′′×4.′′6for the Kitt Peak4m data, 1.′′5×5′′and1.′′5×0.′′6for the MMT data from Thuan et al.1999),the relative?uxes of the emission lines for region e1are in agreement within the errors with those derived by Thuan et al.(1999).
https://www.doczj.com/doc/418459571.html,parison of the elemental abundance ratios,ob-tained for the brightest H ii regions e1(large squares)and e2(small squares)with data for other BCDs(open circles).
The physical conditions and heavy element abun-dances in regions e1and e2were derived following Izotov et al.(1994,1997a)and Thuan et al.(1995).The electron temperatures T e(O iii),T e(S iii),T e(O ii)for the high-, intermediate-and low-ionization regions respectively,the
6N.G.Guseva et al.
Table1.Observed(F(λ))and extinction-corrected(I(λ))?uxes and equivalent widths(EW)of emission lines in the H ii regions e1and e2.
region e1region e2
λ0(?A)Ion F(λ)/F(Hβ)I(λ)/I(Hβ)EW(?A)F(λ)/F(Hβ)I(λ)/I(Hβ)EW(?A)
a in units10?14erg s?1cm?2.
electron number densities N e(S ii),ionization correction factors(ICF),and ionic and total heavy element abun-dances are shown in Table2for both regions.The oxygen abundance12+log(O/H)=7.61±0.01(Z⊙/20)and heavy element abundance ratios for region e1are in good agreement with those derived by Thuan et al.(1999).The oxygen abundance12+log(O/H)=7.62±0.03and heavy element abundance ratios in region e2are consistent with those for region e1within the errors.
In Figure5we compare the heavy element abundance ratios in the two brightest regions of SBS1415+437with data for a sample of low-metallicity BCDs.The Ne/O,S/O,Ar/O and[O/Fe]abundance ratios for the compar-ison sample are taken from Izotov&Thuan(1999),while the Cl/O abundance ratios are collected from Izotov& Thuan(1998)and Izotov et al.(1997a).The heavy element abundance ratios for regions e1(large squares)and e2 (small squares)are in good agreement with those for other BCDs.Note,that the Cl/O ratio does not show any sig-ni?cant increase with increasing oxygen abundance.This conclusion is strengthened by the observations of Esteban et al.(1998,1999a,1999b)who derived log(Cl/O)in the range from–3.28to–3.47for high-metallicity H ii regions in Orion,M17and M8with12+log(O/H)=8.60,8.50
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS 1415+437
7
Fig.6.The blue part of the MMT spectrum of region a 1with labeled emission and absorption lines.
and 8.60,respectively.For comparison,log(Cl/O)=–3.37is derived for the Sun (Anders &Grevesse 1989).The high brightness of regions e 1and e 2allows for a reliable determination of the 4He abundance.Nine He i emission lines are detected in the spectrum of region e 1(Table 1).Two of them,He i λ3889and λ4713,are blended with other lines.Six He i lines are detected in region e 2.The ?ve brightest He i λ3889,λ4471,λ5876,λ6678,λ7065emission lines are used to correct their ?uxes for collisional and ?uorescent enhancement.This is done by minimizing the deviations of the corrected He i line ?ux ratios from the recombination ratios,through vary-ing the electron number density in the He +zone and the optical depth in the He i λ3889emission line.The ?ux of this line was preliminarily corrected for the contribution of the H i λ3889emission line,according to prescriptions of Izotov et al.(1994,1997a).Helium abundances He +/H +,derived from the corrected He i λ4471,λ5876,λ6678line ?uxes and their weighted mean are listed in Table 2.The abundance He +2/H +is added to He +/H +for region e 1,as He ii λ4686is present in its spectrum.Note the lower He abundance derived from the He i λ4471?ux which is most likely due to signi?cant underlying stellar He i λ4471ab-sorption.The e?ect of underlying absorption for the other He i emission lines used in the He abundance determina-tion is much smaller,as they have much larger equivalent widths compared to the He i λ4471emission line (Table 1).The mean 4He mass fractions Y =0.246±0.003and 0.243±0.010in regions e 1and e 2(Table 2)are consistent with the values derived for SBS 1415+437by Izotov &Thuan (1998)and Thuan et al.(1999).They are also con-sistent with the primordial 4He mass fraction Y p =0.244±0.002,derived by extrapolating the Y vs O/H linear regression to O/H =0(Izotov &Thuan 1998),or to Y p =0.245±0.002derived from spectroscopic observations of the two most metal-de?cient BCDs known,I Zw 18and SBS 0335–052(Izotov et al.1999).
Table 2.Element abundances in regions e 1and e 2.
Value
region e 1
region e 2
a ICF is the ionization correction factor.b
[O/Fe]≡log (O/Fe)–log (O/Fe)⊙.
5.Age of the stellar population in the LSB regions
We consider next the spectroscopic and photometric prop-erties of the LSB regions labeled a 1,a 2(slit position 1in Fig.1)and a 3,e 3,a 4(slit position 2),to constrain the age of the stellar populations contributing to the light in those regions.H αand H βemission lines are present in re-gions a 1,a 3and e 3while H γand H δabsorption lines are
8N.G.Guseva et al.
detected in the spectra of all regions except for region e3. This allows us to derive the age of the stellar population using four methods,based on:(1)the time evolution of equivalent widths(EW)of hydrogen emission lines,(2) the time evolution of EW s of hydrogen absorption lines, (3)the comparison of the observed and theoretical spec-tral energy distributions,and(4)the broad-band colours. The requirement of consistency of the ages determined from the reddening-insensitive methods1and2and from the reddening-sensitive methods3and4allows to simul-taneously derive the extinction coe?cient and constrain the SF history(Guseva et al.2001,2003a,2003b).
We measured the?uxes and equivalent widths of the Hαand Hβemission lines and the Hγand Hδabsorption lines in the spectra of the LSB regions,and list them in Tables3and4.Because the Hβemission line is narrower than the absorption line in these regions and does not?ll the absorption component,its?ux was measured using the continuum level at the bottom of the absorption line. This level was chosen by visually interpolating from the absorption line wings to the center of the line.
The extinction coe?cient C(Hβ)in those regions is derived from the Hα/Hβ?ux ratio.We adopt the theo-retical recombination Hα/Hβ?ux ratio of2.8,which is typical for hot low-metallicity H ii regions.No correction for the absorption line equivalent widths has been made. The extinction coe?cients C(Hβ)are shown in Table3.
Hydrogen absorption lines are seen in the spectra of all regions labeled in Fig.1except for the brightest H ii regions e1and e2and the LSB region e3.The blue part of the spectrum of region a1with hydrogen absorption and emission lines is shown in Fig.6.Table4lists the equiva-lent widths with their errors of the Hγand Hδabsorption lines measured in the wavelength intervals or“windows”of Bica&Alloin(1986).The errors include the errors in the?tting of line pro?les with Gaussians and the noise dis-persion in the continuum.A careful placement of the con-tinuum level is very important for deriving accurate EW s. For this purpose,we choose points in the spectrum free of nebular and stellar lines,which were then?tted by cu-bic splines.The uncertainties were estimated from several di?erent measurements of the equivalent widths of hydro-gen absorption lines with independent continuum?ttings. They are of the same order as the errors in Table4.
5.1.Age calibration
The calibration of the age of stellar populations using the equivalent widths of the Hαand Hβnebular emis-sion lines,those of the Hγand Hδstellar absorption lines and the spectral energy distributions is discussed in detail in Guseva et al.(2001,2003a,2003b).Here we only brie?y describe these calibrations.5.1.1.Balmer emission lines
The temporal evolution of the Hαand Hβemission line equivalent widths depends on the star formation history. We consider here the two limiting cases of instantaneous burst and continuous star formation models.The equiv-alent widths for the instantaneous burst model with a heavy element mass fraction Z⊙/20are calculated using the galactic evolution code PEGASE.2(Fioc&Rocca-Volmerange1997).The dependence of the Hαemission line equivalent width on time is shown in Fig.6a of Guseva et al.(2003b)by the thick solid line.These models are ap-propriate for regions e1and e2with strong emission lines. The equivalent widths of Balmer emission lines in region e1(EW(Hα)=998?A and EW(Hβ)=166?A)and region e2(EW(Hα)=872?A and EW(Hβ)=134?A)correspond to an instantaneous burst age of4Myr.
However,for the LSB regions,models with continu-ous star formation are more appropriate.For these mod-els we adopt a constant star formation rate(SFR)within the time interval from t i when star formation starts to t f when it stops.Time is zero now and increases to the past.The equivalent widths of hydrogen emission lines and SEDs for a set of instantaneous burst models(Fioc& Rocca-Volmerange1997)are used to calculate the tempo-ral evolution of EW s for continuous SF with a constant SFR.The temporal dependence of the equivalent widths of the Hαemission line is shown in Fig.6a of Guseva et al.(2003b)for di?erent t i and t f.
5.1.2.Stellar Balmer absorption lines
Another way to derive the age of a stellar population is to use the relation between the Hδand Hγabsorption line equivalent widths and age,derived by Gonz′a lez Delgado, Leitherer&Heckman(1999).Their instantaneous burst models predict a steady increase of the equivalent widths with age from1Myr to1Gyr.However,they did not ex-tend the calculations for ages>～1Gyr when the equivalent widths of the absorption lines decrease with age(Bica& Alloin1986).Hence,each value of the hydrogen absorp-tion line equivalent width corresponds to two values of the age,<～1Gyr and>～1Gyr.This ambiguity can be resolved with the use of other age constraints discussed in this paper.
Furthermore,the models by Gonz′a lez Delgado et al. (1999)probably overestimate the equivalent widths of the absorption lines at ages～1Gyr(Guseva et al.2003b). Therefore,in the age range from1Myr to16.5Gyr in-stead of the calibration by Gonz′a lez Delgado et al.(1999) we use an empirical calibration of the hydrogen absorption line equivalent widths versus age by Bica&Alloin(1986). This calibration is based on the integrated spectra of63 open and globular stellar clusters with known ages,metal-licities and reddenings which can be used as templates for stellar populations formed in an instantaneous burst.For consistency we use the same wavelength intervals or“win-
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS1415+4379 Table3.Fluxes,equivalent widths of the Hαand Hβemission lines and the extinction coe?cients C(Hβ)in the LSB regions.
Telescope Region Distance a Aperture b F(Hα)c F(Hβ)c EW(Hα)d EW(Hβ)d C(Hβ)
4m f a312.6 2.0×7.6 4.88±0.39 1.88±0.2932.81±2.327.72±1.010.0±0.04 e318.4 2.0×2.8 3.69±0.17 1.19±0.14109.80±1.4116.57±0.690.04±0.06
a422.6 2.0×2.8...............
MMT d a110.7 1.5×3.4–5.53±0.22–4.92±0.23
a229.5 1.5×13.2–8.89±0.53–6.07±0.41
a distance in arcsec from the brightest H ii region e1.
b aperture size x×y,where x is the slit width and y the size along the slit in arcsec.
c in?A.
d slit orientation with position angl
e P.A.=22?.
e slit orientation with position angle P.A.=48?.
dows”for Hγand Hδ?ux measurements as Bica&Alloin (1986)(λ4318–4364?A andλ4082–4124?A,respectively).
The behaviour of the empirical Hδabsorption line equivalent width with the age for an instantaneous burst (Bica&Alloin1986)is shown in Fig.6b of Guseva et al. (2003b)by the thick solid line.
The temporal evolution of the Hγand Hδabsorption line equivalent widths in the case of continuous SF is calculated similarly to that of the Hαand Hβemission line equivalent widths described in the section5.1.1.More speci?cally,we use the empirical equivalent widths of hy-drogen absorption lines(Bica&Alloin1986)and SEDs for instantaneous bursts(Fioc&Rocca-Volmerange1997)to calculate the temporal evolution of EW s in the case of continuous SF with constant SFR.The results are shown in Fig.6b of Guseva et al.(2003b)for SF with di?erent t i and t f.
5.1.3.Spectral energy distribution
The shape of the spectrum re?ects the properties of the stellar population.However,it is also dependent on the reddening.A precise determination of the extinction can be done only for the two brightest H ii regions e1and e2which possess many strong hydrogen emission lines (Table1).We derived an extinction coe?cient C(Hβ)=0 in these regions.In the LSB regions a1,a3and e3,only Hαand Hβemission lines are present.The extinction coe?-cients obtained from the Hα/Hβ?ux ratio in these regions are small(Table3).However,they are more uncertain as compared to the ones in regions e1and e2because of the weakness of the emission lines and signi?cant contribution of the stellar absorption lines.Hαand Hβemission lines are not detected in the other LSB regions.Therefore,the observed SED cannot directly give information on the age, but should be used together with the methods discussed in Sect.5.1.1and5.1.2for simultaneous determination of the age and interstellar extinction.
We used the galactic evolution code PEGASE.2(Fioc &Rocca-Volmerange1997)to produce a grid of theoreti-cal SEDs for an instantaneous burst of star formation with ages ranging between0and10Gyr,and a heavy element mass fraction of Z=Z⊙/20.The SEDs for continuous SF in the time interval between t i ago and t f ago are derived by integration of instantaneous burst SEDs.
5.2.Ages of the stellar populations in the LSB regions In this section we derive self-consistently the ages of the stellar populations in the LSB regions using:1)the equiv-alent widths of emission lines,2)the equivalent widths of absorption lines,3)the SEDs and4)the colours.For this we adopt a continuous SF scenario with constant or variable SFR.In the latter case we consider a sim-pli?ed scenario with two time intervals of SF,which we call young and old,with di?erent SFRs.To quantify
10N.G.Guseva et
al.
Fig.7.Spectra of region a 2on which synthetic SEDs are superposed.Synthetic SEDs are calculated for stellar populations forming continuously during one (a )or two (b –g )time intervals.In the case of two intervals the SFR is constant within each interval but varies from one interval to another one by a factor b =SFR(young)/SFR(old).The spectra in left panel are corrected for interstellar extinction with C (H β)=0.1.The extinction coe?cient C (H β)is set to 0in right panel.Time intervals,parameters b and predicted EW s of the H αemission and H δabsorption lines are indicated (see explanations in Sect.5.2).
the di?erence in SFRs we introduce the parameter b =SFR(young)/SFR(old).Because of the noisy spectrum of region e 3and the signi?cant contamination by nebular emission we were not able to measure equivalent widths of absorption lines in that region.Therefore,we exclude it from the analysis.For the remaining LSB regions,the model predictions providing the best ?ts to the observed SEDs are shown in Table 5.For each region we show the age range of one or two SF episodes,the parameter b ,the mass ratio M y /M o of the young-to-old populations,the model equivalent widths of hydrogen lines,the ex-tinction coe?cients C (H β)derived from the best match between observed and calculated SEDs,and the intrinsic and reddened (V ?I )colours (see Sect.5.2.1).We use the relation E (V ?I )=0.891C (H β)(e.g.,Aller 1984)to correct for reddening.Our young and old stellar popu-lations in Table 5include stars with ages not older than 250Myr (log t =8.4)and not younger than 160Myr (log t =8.2),respectively.These de?nitions di?er from those
conventionally used.In fact,the old stellar population in our case includes not only several Gyr old stars but also intermediate-age stars with age <～1Gyr.Negative EW s denote absorption lines,positive EW s refer to emission lines.Models with highlighted EW s are those in which the equivalent widths are not reproduced well despite a good ?t of the observed SEDs (compare model EW s in Table 5with observed EW s in Tables 3and 4).
We show in Fig.7the observed and predicted SEDs in the outer LSB region a 2(MMT observations)with no emission features.The H γand H δabsorption lines in this region as well as in the other outer region a 4(4m telescope observations)are not contaminated by nebular emission from young stellar populations.Hence,the absorption line equivalent widths in regions a 2and a 4are more accurate than in other LSB regions (Table 4).
We consider several SF histories and vary extinction in the LSB regions to put constraints on the age of their stellar populations.Figure 7shows the spectra of region a 2
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS1415+43711 Table5.Predicted equivalent widths of emission and absorption lines,extinction coe?cients and(V–I)colours from models of continuous star formation.
Age range a modeled EW modeled(V–I)d MMT e a17.1–7.5......–6.3–5.2 2.213.80.270.2110.452
7.05–7.59.4–10240.07–6.0–5.1 2.513.20.000.4560.456
7.1–7.59.4–10660.18–6.2–5.2 2.212.90.120.3350.442
7.11–7.59.4–10400 1.00–6.2–5.2 1.913.60.220.2420.438
a27.1–8.2......–8.9–7.90.6 3.40.100.3500.439
7.1–8.28.2–9.31008.1–8.9–7.90.7 3.80.100.3580.447
7.1–7.68.9–9.3190.5–6.8g–5.6 1.79.7g0.100.3420.431
7.1–8.29.4–10100019.7–8.8–7.90.7 3.90.100.3520.441
7.1–8.28.2–9.370.6–9.2–7.90.5 2.70.000.4400.440
7.1–7.68.9–9.390.2–7.1g–5.8 1.47.8g0.000.4180.418
7.1–8.29.4–10170.3–8.6–7.70.6 3.30.000.4410.441
a duration of SF in log t(t in yr).
b b≡SFR(young)/SFR(old).
c EW in?A.
d intrinsic colour is that for th
e stellar population in the absence o
f extinction.(V?I)reddened=(V?I)intrinsic+0.891C(Hβ).
e slit orientation with position angle P.A.=22?.
f slit orientation with position angle P.A.=48?.
g EW s do not?t observations.
on which are superposed the synthetic SEDs with di?erent SF histories which best?t it.
We have assumed two extinction coe?cients:C(Hβ)= 0.1,derived by Thuan et al.(1999),and corresponding to A(V)～0.2,and C(Hβ)=0.
The model SEDs,adopting C(Hβ)=0.1are shown in Fig.7,left panel.The observed properties of region a2can be reproduced by a single young stellar population with age between12Myr and160Myr,if a small amount of extinction is assumed(Fig.7a).There is no need to invoke an older stellar population which,if present,has to be much smaller in mass than the young stellar population. We note that there is no ongoing SF in this region.The most recent SF in region a2stopped at time>～12Myr ago, otherwise its spectrum would have shown a detectable Hαemission line(Fig.6a in Guseva et al.2003b).
Next we consider SF scenarios with a varying SFR which include older stellar populations with an age of up to2Gyr(Fig.7b–7c)and10Gyr(Fig.7d).But even in these cases,the young population completely dominates the light and mass of region a2(Table5).
An upper limit to the age of region a2can be obtained by assuming no extinction,i.e.C(Hβ)=0(Fig.7,right panel).Then the observed SED cannot be reproduced by a synthetic SED with stars forming between12Myr and 160Myr ago,as the latter is too blue.However,by vary-ing the parameter b,the observed SED can be reproduced by SEDs of stellar populations with other SF scenarios. In Figs.7b–7d,7e–7g,we show the best?ts labeled by the adopted value of b.We exclude the models shown in Fig.7c and7f because they do not?t the observed equiva-lent widths of Hαand Hδ.The remaining two models with C(Hβ)=0satisfy all observational constraints.In these models,the SFRs for the young population are respec-tively7times(Fig.7e)and17times(Fig.7g)larger than SFRs for the old population.These ratios are,however, signi?cantly smaller than the corresponding parameters b in the case with C(Hβ)=0.1.The relative mass fraction of the young stellar population is therefore smaller in the extinction-free case,being M y/M o=0.6(Fig.7e)and0.3 (Fig.7g),respectively.Therefore,the presence of a2Gyr old or even10Gyr old population is not excluded in re-gion a2,which would however not dominate the optical
12N.G.Guseva et
al.
Fig.8.(a )V surface brightness distribution along the slit oriented at position angle P.A.=22?.The origin is set at the brightest H ii region e 1.(b )(V ?I )colour distribution along the slit with position angle P.A.=22?.(c )V surface brightness distribution along the slit oriented at position angle P.A.=48?.The origin is set at the brightest H ii region e 1.(d )(V ?I )colour distribution along the slit with position angle P.A.=48?.The locations of di?erent regions are labeled in (b )and (d ).Filled squares show the total modeled colours (stellar plus gaseous emission)for region e 1.Other symbols show the colours predicted for the LSB regions by the models considered (Table 5).emission.If the extinction is non-zero,which is likely the case,then there is no need to invoke a signi?cant old pop-ulation to explain the observed properties of region a 2.It is likely that for other regions,a 1and a 3(Table 5),the extinction is even larger.
Similar consideration for region a 4shows that the mass fraction of the old stellar population is small even in the absence of extinction.In any case,the old stellar popu-lation,if present does not contribute signi?cantly to the luminosity.All the observed properties of this region can be reproduced with a young stellar population formed be-tween 12Myr and 160Myr ago.However,the presence of an older stellar population cannot be excluded in that case,but one needs to increase the parameter b to match the observations (Table 5).
If some extinction is present in region a 4,then our age upper limits will decrease.There is some hint that the extinction may increase with decreasing distance to the brightest H ii region e 1.Indeed,by considering models which include also a 10Gyr old population and C (H β)=0,we ?nd from Table 5that the closer a region is to the brightest part of the galaxy (region a 1compared to region a 2,region a 3compared to region a 4),the smaller is
the relative mass M y /M o of the young stellar population.This is in contrast to the trend found in BCDs where the relative mass of the young stellar population decreases outwards.Hence,we conclude,that the extinction in SBS 1415+437is larger in the inner brighter regions.
In summary,our spectroscopic analysis of the LSB re-gions favors a relatively young luminosity-weighted age of the stars populating those regions.A model with a constant SFR continuing from 10Gyr ago until now is de?nitely excluded.An old population >～2Gyr could be present only in models with very speci?c SF scenarios,with a very low SF activity during the ?rst 2–10Gyr pe-riod,a very high star formation rate during the last ～(10–200)Myr,and a quiescent period in between.If,however,low SF activity has occurred in the period between ～200Myr and 2Gyr ago,then there is no need to invoke a stellar population with age >～2Gyr,and all the spectro-scopic properties of the LSB regions can be explained by only young and intermediate-age stellar populations.
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS1415+43713 Table6.(V?I)colours of the extended LSB components in some irregular and BCD galaxies.
No.Galaxy(V?I)LSB a Telescope b12+log(O/H)Telescope c Ref.d Ref.e
a colour corrected for reddening in our Galaxy.E(V?I)Galaxy are taken from the NED.
b telescope used to obtain photometry.
c telescope use
d to obtain spectroscopic data.
d referenc
e for the photometry.
e reference for the chemical abundance.
?our rough estimate.
??oxygen abundance of the main component I Zw18NW+SE.
???oxygen abundance is calculated using the observed data by Kobulnicky et al.(1999)and calibration by Pilyugin(2000). References:(1)Crone et al.2002;(2)Drozdovsky et al.2001;(3)Guseva et al.2001;(4)Izotov et al.2001a;(5)Izotov et al. 2001b;(6)Izotov et al.1999;(7)Izotov&Thuan2002;(8)Izotov&Thuan1999;(9)Izotov et al.1997a;(10)Kobulnicky& Skillman1996;(11)Kobulnicky et al.1999;(12)Papaderos et al.1998;(13)Papaderos et al.2002;(14)Storchi-Bergmann et al.1994;(15)Thuan et al.1996;(16)Vaceli et al.1997;(17)Guseva et al.2003a;(18)Guseva et al.2003b;(19)this paper.
5.2.1.Age from the colour distributions
From the HST images,we derived V and I surface bright-ness and colour distributions for the regions covered by the spectroscopic observations with the MMT(Fig.8a and8b)and the KPNO4m telescope(Fig.8c and8d). Note the trend for the(V?I)colour of the LSB com-ponent to decrease with increasing distance from region e1,especially for the KPNO4m data(Fig.8d).This is again suggestive of larger extinction in the brighter re-gions.We compare the observed colours with predictions from our population synthesis modeling.The results of this comparison are shown in Figs.8b and8d.The pre-dicted colours,obtained from convolving the theoretical SEDs with the appropriate?lter bandpasses,are shown by di?erent symbols.The transmission curves for the Johnson V and Cousins I bands are taken from Bessell(1990).The zero points are from Bessell,Castelli&Plez(1998).
Since the contribution of ionized gas emission to the total brightness of region e1is signi?cant,the theoretical SED for this region has been constructed using a4Myr old stellar population SED for a heavy element mass fraction Z=Z⊙/20to which the gaseous continuum SED and the observed emission lines were added(see Guseva et al. 2001).For comparison with the observed colour at P.A. =22?,we reddened the predicted colour of region e1by an amount corresponding to C(Hβ)=0.11(Table3in Thuan et al.1999),and at P.A.=48?we adopted C(Hβ) =0(Table1).The observed colour of region e1is very blue,(V–I)～–0.4(Fig.8b and8d),and cannot be reproduced by a4Myr old stellar population alone((V –I)～0.1).Strong gaseous continuum and line emission need to be added(Table1).
On the other hand,in all the LSB regions the contri-bution of the gaseous emission to the total?ux is negligi-
14N.G.Guseva et
al.
Fig.9.Dependence of the (V ?I )colours of the LSB component (a )and logarithm of the derived ages (b )on the oxygen abundance for the dwarf irregular and BCD galaxies from our sample.Dashed lines in (a )show the-oretical dependences of the (V –I )colour on the oxygen abundance for an instantaneous burst calculated using the galactic evolution code PEGASE.2(Fioc &Rocca-Volmerange 1997)in the range of ages (in logarithmic scale)log t i between 7.1and 10.0(t i in yr).Solid lines show models in which stars are forming continuously at a constant SFR between t f =0and di?erent t i ,where log t i varies between 7.5and 10.0.The observed colours are corrected only for reddening in our Galaxy.The ages in (b )are from Izotov et al.(2001b)(I Zw 18),Papaderos et al.(1998)(SBS 0335–052),Guseva et al.(2001)(SBS 0940+544),Guseva et al.(2003b)(HS 1442+4250)and this paper (SBS 1415+437).
ble.In Figs.8b and 8d we show by di?erent symbols the colours of the LSB regions with various star formation his-tory (Table 5).The total colour (stellar plus gaseous emis-sion)of region e 1is shown by a ?lled squares.The agree-ment between the (V ?I )colours and those derived from the spectral energy distributions is very good.However,some uncertainties in the colours may be introduced by the uncertainties in the reddening curves and the ratios of total to selective extinction R =A (V )/E (B ?V ).We use R =3.2by Aller (1984),based on the reddening curve by Seaton (1979).Schlegel,Finkbeiner &Davis (1998)give a slightly di?erent R =3.315.Nevertheless,because the extinction in the studied regions is small,the errors intro-
duced by the use of di?erent reddening curves and R are less than 2%in the V band and negligible in the I band.The (B ?V )colour of ～0.2mag,derived from the SEDs of the LSB regions,is also consistent with the observed value,derived from the B and V SBPs,which are shown in Fig.3a.
https://www.doczj.com/doc/418459571.html,parison of the LSB component photometric
properties for galaxies with di?erent metallicities
Our comprehensive studies of selected galaxies with oxy-gen abundances 12+log(O/H)<～7.6and blue LSB com-ponents (SBS 0335–052,Izotov et al.1997b,Papaderos et al.1998;I Zw 18,Izotov et al.2001b,Papaderos et al.2002;SBS 0940+544,Guseva et al.2001;Tol 1214–277,Fricke et al.2001;Tol 65,Papaderos et al.1999;SBS 1129+576,Guseva et al.2003a;HS 1442+4250,Guseva et al.2003b;SBS 1415+437,this paper)have led us to the conclusion that these galaxies might be young.This is in contrast to the large age estimates for some well-studied higher-metallicity irregular and BCD galaxies,such as VII Zw 403and UGCA 290(Schulte-Ladbeck et al.1998;Crone et al.2002).To investigate this apparent inconsis-tency we therefore compare the (V –I )colours of the LSB components ((V –I )LSB )of the galaxies from our sample with those in galaxies where a large age was derived from colour-magnitude diagrams (CMD).
In Table 6,we show the oxygen abundances and (V –I )colours of the LSB components in several dwarf irreg-ular and BCD galaxies.The telescopes used for photo-metric and spectroscopic observations are also given in the Table.Ground-based photometric data in V and I were obtained with the 2.1m KPNO telescope by Y.Izotov and R.Green.The HST photometric data were retrieved from the archive of the Space Telescope Science Institute (STScI)5.We included in the sample only galaxies with low internal and/or foreground interstellar extinction to avoid uncertainties introduced by the correction of the (V ?I )colour for reddening.Thus,we do not include the nearby star-forming galaxy NCG 1569studied with HST ,for example.The chemical abundances for the majority of galaxies are obtained from spectroscopic observations of their H ii regions.An exception is I Zw 18C,the faint component of the BCD I Zw 18,where no emission lines of heavy elements were detected.Therefore,for I Zw 18C we adopt the oxygen abundance derived for the bright main body of I Zw 18.(V ?I )colours of the galaxies in Table 6are corrected for reddening in our Galaxy,with E (V ?I )Galaxy taken from the NASA/IPAC Extragalactic Database (NED).
The dependence of the (V –I )LSB colours on oxygen abundance for 26selected galaxies is shown in Fig.9a.Thin dashed lines represent theoretical dependences for an instantaneous burst in the age range from log t i =7.1to log t i =10.0(t i in yr).The models for continuous star
Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies.III.SBS1415+43715
formation are shown by thick solid lines.These models are calculated for a constant SFR which started at time t i,with log t i between7.5and10.0and continuing un-til now(t f=0).The blueing of the(V?I)colour with decreasing oxygen abundance is in agreement with model predictions.However,this blueing trend for galaxies with 12+log(O/H)<～7.6is too steep to be explained only by metallicity e?ects.The blue colours of the LSB compo-nents of these low-metallicity BCDs are also not due to ionized gas emission,as the latter dominates the outer parts of only two BCDs:I Zw18(Izotov et al.2001b; Papaderos et al.2002)and SBS0335–052(Izotov et al. 1997b;Papaderos et al.1998).In other galaxies,includ-ing I Zw18C,the LSB component emission has mainly a stellar origin.The steep trend cannot be explained by red-dening e?ects because the interstellar extinction derived from the spectroscopic observations is small for the galax-ies shown in Fig.9a.Therefore,it is likely that the blueing is mainly due to a change in the age of the stellar popula-tions,and that low-metallicity galaxies are younger than high-metallicity ones.All objects with12+log(O/H)<～7.6 and(V–I)LSB<～0.6mag are in the range of colours pre-dicted for ages<～1–2Gyr by instantaneous and continuous models of star formation.On the other hand,galaxies with (V–I)LSB>～0.7mag are likely to be older,with ages～10 Gyr.Yi(2003)has analysed the uncertainties in the syn-thetic integrated(V?I)colours caused by uncertainties in the stellar evolutionary models,population synthesis tech-niques and stellar atmosphere models.He has shown that, despite all the uncertainties,a(V–I)<～0.65–0.75mag can be attributed to an intermediate-age stellar population with an age not larger than2Gyr,in the case of an in-stantaneous burst of star formation,in agreement with the age derived here from the PEGASE.2models(dashed lines in Fig.9a).The smaller luminosity-weighted age of galax-ies with blue LSB components in Fig.9a is supported by the detailed analysis of the spectroscopic and photometric properties of some of these galaxies,as demonstrated in this series of papers.
Izotov&Thuan(1999)have suggested that the oxy-gen abundance may be a good age indicator.That this appears to be the case is shown in Fig.9b where a clear trend of increasing age of the LSB stellar population with increasing oxygen abundance is seen for5star-forming galaxies with available data.The ages for4galaxies(I Zw 18,Izotov et al.2001b;SBS0940+544,Guseva et al.2001; HS1442+4250,Guseva et al.2003b;SBS1415+437,this paper)are determined by the four methods described be-fore.The age for SBS0335–052(Papaderos et al.1998)is derived using only colours and SEDs.This is because its LSB component is embedded into the H ii region produced by the young central clusters and no absorption lines are present in the spectra.
6.Conclusions
The results of a detailed photometric and spectroscopic study of the metal-de?cient blue compact dwarf galaxy SBS1415+437are presented.Hαimages and spectra in the optical range have been obtained with the Kitt Peak 2.1m and4m telescopes,respectively.A B image has been obtained with the2.2m Calar Alto telescope.These data are supplemented by HST/WFPC2V and I images and MMT spectra from Thuan et al.(1999).The main conclu-sions of this study can be summarized as follows:
1.SBS1415+437is a nearby(D=11.4Mpc)low-
metallicity cometary BCD with two bright H ii regions in the SW part of the elongated low-surface-brightness (LSB)stellar component.The scale lengthsαof the LSB component,obtained from surface brightness pro-?les(SBPs)in V and I are both～0.3kpc,in excellent agreement with those in Thuan et al.(1999).The ob-served(V?I)colour of the brightest H ii region is very blue,～–0.4mag,due to the combined e?ects of a young stellar population and ionized gas emis-sion.The colours of the low-surface-brightness com-ponent are much redder(～0.4–0.5mag)and roughly constant in the outer parts of the galaxy.A deeper
B band SBP of SBS1415+437reveals at intermedi-
ate and large radii two exponential intensity regimes with a scale length of0.3and0.27kpc,respectively.
The inner one(4′′<～R?<～13′′)can be identi?ed with the exponential component derived from HST V and
I data.The outer one,which dominates for R?>～16′′,
is>～0.3mag fainter than the inner component.
2.In the two brightest H ii regions we derive oxygen
abundances of12+log(O/H)=7.61±0.01and7.62±0.03(Z～Z⊙/20).These values agree well with previous determinations(Thuan et al.1999).Other heavy element-to-oxygen abundance ratios for these H ii regions are also in good agreement with mean ratios derived from previous studies of BCDs(Thuan et al.
1995;Izotov&Thuan1999).
3.The4He mass fractions Y=0.246±0.003and0.243
±0.010,derived for the brightest H ii regions of SBS 1415+437,are in good agreement with previous deter-minations for this galaxy and with the primordial4He mass fraction Y p=(0.244–0.245)±0.002(Izotov& Thuan1998;Izotov et al.1999).
4.We use four di?erent methods and di?erent SF scenar-
ios to derive the age of the stellar populations in the LSB component of the galaxy.For the outer LSB re-gions,the equivalent widths of the Hαand Hβemission lines,the equivalent widths of the Hγand Hδabsorp-tion lines,the spectral energy distributions and the (V?I)colours are reproduced quite well by models in which only a young stellar population(t<～250Myr) is present.For those regions,only a small extinction with C(Hβ)in the range0–0.1is needed.An older stellar population,if present,does not contribute sub-stantially to the optical luminosity of those outer re-gions.For region a1,located closer to the brightest H ii region,a larger extinction(C(Hβ)=0.22)is required to?t the observational data by the same young stellar population.The assumption of C(Hβ)=0in all regions
16N.G.Guseva et al.
would require an increase of the relative fraction of the old stellar population from the outer LSB parts to the inner bright H ii regions,which would be contrary to the trend observed in the majority of BCDs,where the relative contribution of old stars increases outwards.
Assuming no extinction,we?nd that the upper limit to the mass of the old stellar population in SBS 1415+437,formed between2.5Gyr and10Gyr,is not greater than～(1/20–1)of the mass of the stellar pop-ulation formed during the last～250Myr.Depending on the region considered,this also implies that the star formation rate during the most recent star formation rate in SBS1415+437must be20to1000times greater than the SFR at ages>～2.5Gyr.
5.We compare the(V?I)colours of the LSB components
and the oxygen abundances of a sample of26low-metallicity dwarf irregular and BCD galaxies,includ-ing SBS1415+437.It is shown that the LSB compo-nents are systematically bluer in the lower-metallicity galaxies.However,the observed trend is too steep to be explained only by metallicity e?ects.Therefore, it is likely that lower-metallicity galaxies have also younger populations.In particular,the luminosity-weighted ages of galaxies with LSB colours of(V?I) <～0.6are probably not greater than1–2Gyr. Acknowledgements.N.G.G.has been supported by DFG grant
436UKR17/2/02and Y.I.I.acknowledges the G¨o ttingen Academy of Sciences for a Gauss professorship.N.G.G. and Y.I.I.have been partially supported by Swiss SCOPE 7UKPJ62178grant.They are grateful for the hospitality of the G¨o ttingen Observatory.Y.I.I.and T.X.T.have been par-tially supported by NSF grant AST-02-05785.Research by P.P. and K.J.F.has been supported by the Deutsches Zentrum f¨u r Luft–und Raumfahrt e.V.(DLR)under grant50OR 99077.K.G.N.acknowledges the support from the Deutsche Forschungsgemeinschaft(DFG)grants FR325/50-1and FR 325/50-2.This research has made use of the NASA/IPAC Extragalactic Database(NED)which is operated by the Jet Propulsion Laboratory,California Institute of Technology, under contract with the National Aeronautics and Space Administration.
References
Aller,L.H.1984,Physics of Thermal Gaseous Nebulae, Dordrecht:Reidel
Anders,E.,&Grevesse,N.1989,Geochim.Cosmochim.Acta, 53,197
Bessell,M.S.1990,PASP,102,1181
Bessell,M.S.,Castelli,F.,&Plez,B.1998,A&A,333,231 Bica,E.,&Alloin,D.1986,A&AS,66,171
Christian,C.A.,Adams,M.,Barnes,J.V.,et al.1985,PASP, 97,363
Crone,M.M.,Schulte-Ladbeck,R.E.,Greggio,L.,&Hopp, U.2002ApJ,567,258
Drozdovsky,I.O.,Schulte-Ladbeck,R.E.,Hopp,U.,Crone, M.M.,&Greggio,L.2001,ApJ,551,L135
Esteban,C.,Peimbert,M.,Torres-Peimbert,S.,&Escalante, V.1998,MNRAS,295,401Esteban,C.,Peimbert,M.,Torres-Peimbert,S.,Garcia-Rojas, J.,&Rodriguez,M.1999a,ApJS,120,113
Esteban, C.,Peimbert,M.,Torres-Peimbert,S.,&Garcia-Rojas,J.1999b,Rev.Mex.Astron.Astro?z.,35,65 Fioc,M.,&Rocca-Volmerange,B.1997,A&A,326,950 Fricke,K.J.,Izotov,Y.I.,Papaderos,P.,Guseva,N.G.,& Thuan,T.X.2001,AJ,121,169
Gonz′a lez Delgado,R.M.,Leitherer,C.,&Heckman,T.M.
1999,ApJS,125,489
Guseva,N.G.,Izotov,Y.I.,Papaderos,P.,et al.2001,A&A, 378,756
Guseva,N.G.,Papaderos,P.,Izotov,Y.I.,et al.2003a,A&A, in press
Guseva,N.G.,Papaderos,P.,Izotov,Y.I.,et al.2003b,A&A, in press
Izotov,Y.I.,&Thuan,T.X.1998,ApJ,500,188
Izotov,Y.I.,&Thuan,T.X.1999,ApJ,511,639
Izotov,Y.I.,&Thuan,T.X.2002,ApJ,567,875
Izotov,Y.I.,Thuan,T.X.,&Lipovetsky,V.A.1994,ApJ, 435,647
Izotov,Y.I.,Thuan,T.X.,&Lipovetsky,V.A.1997a,ApJS, 108,1
Izotov,Y.I.,Lipovetsky,V.A.,Cha?ee,F.H.,et al.1997b, ApJ,476,698
Izotov,Y.I.,Cha?ee,F.H.,Foltz,C.B.,et al.1999,ApJ,527, 757
Izotov,Y.I.,Cha?ee,F.H.,&Green,R.F.2001a,ApJ,562, 727
Izotov,Y.I.,Cha?ee,F.H.,Foltz,C.B.,et al.2001b,ApJ, 560,222
Kobulnicky,H.A.,&Skillman,E.D.1996,ApJ,471,211 Kobulnicky,H.A.,Kennicutt,R.C.,Jr.,&Pizagno,J.L.1999, ApJ,514,544
Noeske,K.G.,Guseva,N.G.,Fricke,K.J.,et al.2000,A&A, 361,33
Papaderos,P.,Loose,H.-H.,Thuan,T.X.,&Fricke,K.J.
1996,A&AS,120,207
Papaderos,P.,Izotov,Y.I.,Fricke,K.J.,Thuan,T.X.,& Guseva,N.G.1998,A&A,338,43
Papaderos,P.,Fricke,K.J.,Thuan,T.X.,Izotov,Y.I.,& Nicklas,H.1999,A&A,352,57
Papaderos,P.,Izotov,Y.I.,Thuan,T.X.,et al.2002,A&A, 393,461
Pilyugin,L.S.2001,A&A,369,594
Seaton,M.J.1979,MNRAS,187,73
Schlegel,D.J.,Finkbeiner,D.P.,&Davis,M.1998,ApJ,500, 525
Schulte-Ladbeck,R.E.,Crone,M.M.,&Hopp,U.1998,ApJ, 493,23
Storchi-Bergmann,T.,Calzetti,D.,&Kinney,A.L.1994,ApJ, 429,572
Thuan,T.X.,Izotov,Y.I.,&Lipovetsky,V.A.1995,ApJ, 445,108
Thuan,T.X.,Izotov,Y.I.,&Lipovetsky,V.A.1996,ApJ, 463,120
Thuan,T.X.,Izotov,Y.I.,&Foltz,C.B.1999,ApJ,525,105 Vaceli,M.S.,Viegas,S.M.,Gruenwald,R.,&De Souza,R.
E.1997,AJ,114,1345
Yi,S.K.2003,ApJ,582,202
脐带间充质干细胞的研究进展 间充质干细胞（mesenchymal stem cells,MSC S ）是来源于发育早期中胚层 的一类多能干细胞[1-5]，MSC S 由于它的自我更新和多项分化潜能，而具有巨大的 治疗价值 ,日益受到关注。MSC S 有以下特点：(1)多向分化潜能，在适当的诱导条件下可分化为肌细胞[2]、成骨细胞[3、4]、脂肪细胞、神经细胞[9]、肝细胞[6]、心肌细胞[10]和表皮细胞[11, 12]；(2)通过分泌可溶性因子和转分化促进创面愈合；(3) 免疫调控功能，骨髓源（bone marrow ）MSC S 表达MHC-I类分子，不表达MHC-II 类分子，不表达CD80、CD86、CD40等协同刺激分子，体外抑制混合淋巴细胞反应，体内诱导免疫耐受[11, 15]，在预防和治疗移植物抗宿主病、诱导器官移植免疫耐受等领域有较好的应用前景；(4)连续传代培养和冷冻保存后仍具有多向分化潜能，可作为理想的种子细胞用于组织工程和细胞替代治疗。1974年Friedenstein [16] 首先证明了骨髓中存在MSC S ，以后的研究证明MSC S 不仅存在于骨髓中，也存在 于其他一些组织与器官的间质中：如外周血[17]，脐血[5]，松质骨[1, 18]，脂肪组织[1]，滑膜[18]和脐带。在所有这些来源中，脐血(umbilical cord blood)和脐带(umbilical cord)是MSC S 最理想的来源，因为它们可以通过非侵入性手段容易获 得，并且病毒污染的风险低，还可冷冻保存后行自体移植。然而，脐血MSC的培养成功率不高[19, 23-24]，Shetty 的研究认为只有6%，而脐带MSC的培养成功率可 达100%[25]。另外从脐血中分离MSC S ，就浪费了其中的造血干/祖细胞(hematopoietic stem cells/hematopoietic progenitor cells,HSCs/HPCs) [26, 27]，因此，脐带MSC S (umbilical cord mesenchymal stem cells, UC-MSC S )就成 为重要来源。 一．概述 人脐带约40 g, 它的长度约60–65 cm, 足月脐带的平均直径约1.5 cm[28, 29]。脐带被覆着鳞状上皮，叫脐带上皮，是单层或复层结构，这层上皮由羊膜延续过来[30, 31]。脐带的内部是两根动脉和一根静脉，血管之间是粘液样的结缔组织，叫做沃顿胶质，充当血管外膜的功能。脐带中无毛细血管和淋巴系统。沃顿胶质的网状系统是糖蛋白微纤维和胶原纤维。沃顿胶质中最多的葡萄糖胺聚糖是透明质酸，它是包绕在成纤维样细胞和胶原纤维周围的并维持脐带形状的水合凝胶，使脐带免受挤压。沃顿胶质的基质细胞是成纤维样细胞[32]，这种中间丝蛋白表达于间充质来源的细胞如成纤维细胞的，而不表达于平滑肌细胞。共表达波形蛋白和索蛋白提示这些细胞本质上肌纤维母细胞。 脐带基质细胞也是一种具有多能干细胞特点的细胞，具有多项分化潜能，其 形态和生物学特点与骨髓源性MSC S 相似[5, 20, 21, 38, 46]，但脐带MSC S 更原始，是介 于成体干细胞和胚胎干细胞之间的一种干细胞，表达Oct-4, Sox-2和Nanog等多
With的用法全解 with结构是许多英语复合结构中最常用的一种。学好它对学好复合宾语结构、不定式复合结构、动名词复合结构和独立主格结构均能起很重要的作用。本文就此的构成、特点及用法等作一较全面阐述，以帮助同学们掌握这一重要的语法知识。 一、 with结构的构成 它是由介词with或without+复合结构构成，复合结构作介词with或without的复合宾语，复合宾语中第一部分宾语由名词或代词充当，第二部分补足语由形容词、副词、介词短语、动词不定式或分词充当，分词可以是现在分词，也可以是过去分词。With结构构成方式如下： 1. with或without-名词/代词+形容词； 2. with或without-名词/代词+副词； 3. with或without-名词/代词+介词短语； 4. with或without-名词/代词 +动词不定式； 5. with或without-名词/代词 +分词。 下面分别举例： 1、 She came into the room，with her nose red because of cold.（with+名词+形容词，作伴随状语）
2、 With the meal over ， we all went home.（with+名词+副词，作时间状语） 3、The master was walking up and down with the ruler under his arm。（with+名词+介词短语，作伴随状语。） The teacher entered the classroom with a book in his hand. 4、He lay in the dark empty house，with not a man ，woman or child to say he was kind to me.（with+名词+不定式，作伴随状语）He could not finish it without me to help him.（without+代词 +不定式，作条件状语） 5、She fell asleep with the light burning.（with+名词+现在分词，作伴随状语） Without anything left in the with结构是许多英 语复合结构中最常用的一种。学好它对学好复合宾语结构、不定式复合结构、动名词复合结构和独立主格结构均能起很重要的作用。本文就此的构成、特点及用法等作一较全面阐述，以帮助同学们掌握这一重要的语法知识。 二、with结构的用法 with是介词，其意义颇多，一时难掌握。为帮助大家理清头绪，以教材中的句子为例，进行分类，并配以简单的解释。在句子中with结构多数充当状语，表示行为方式，伴随情况、时间、原因或条件（详见上述例句）。 1.带着，牵着…… (表动作特征)。如： Run with the kite like this.
脐带血造血干细胞库管理办法（试行） 第一章总则 第一条为合理利用我国脐带血造血干细胞资源，促进脐带血造血干细胞移植高新技术的发展，确保脐带血 造血干细胞应用的安全性和有效性，特制定本管理办法。 第二条脐带血造血干细胞库是指以人体造血干细胞移植为目的，具有采集、处理、保存和提供造血干细胞 的能力，并具有相当研究实力的特殊血站。 任何单位和个人不得以营利为目的进行脐带血采供活动。 第三条本办法所指脐带血为与孕妇和新生儿血容量和血循环无关的，由新生儿脐带扎断后的远端所采集的 胎盘血。 第四条对脐带血造血干细胞库实行全国统一规划，统一布局，统一标准，统一规范和统一管理制度。 第二章设置审批 第五条国务院卫生行政部门根据我国人口分布、卫生资源、临床造血干细胞移植需要等实际情况，制订我 国脐带血造血干细胞库设置的总体布局和发展规划。 第六条脐带血造血干细胞库的设置必须经国务院卫生行政部门批准。 第七条国务院卫生行政部门成立由有关方面专家组成的脐带血造血干细胞库专家委员会（以下简称专家委
员会），负责对脐带血造血干细胞库设置的申请、验收和考评提出论证意见。专家委员会负责制订脐带血 造血干细胞库建设、操作、运行等技术标准。 第八条脐带血造血干细胞库设置的申请者除符合国家规划和布局要求，具备设置一般血站基本条件之外， 还需具备下列条件： （一）具有基本的血液学研究基础和造血干细胞研究能力； （二）具有符合储存不低于1 万份脐带血的高清洁度的空间和冷冻设备的设计规划； （三）具有血细胞生物学、HLA 配型、相关病原体检测、遗传学和冷冻生物学、专供脐带血处理等符合GMP、 GLP 标准的实验室、资料保存室； （四）具有流式细胞仪、程控冷冻仪、PCR 仪和细胞冷冻及相关检测及计算机网络管理等仪器设备； （五）具有独立开展实验血液学、免疫学、造血细胞培养、检测、HLA 配型、病原体检测、冷冻生物学、 管理、质量控制和监测、仪器操作、资料保管和共享等方面的技术、管理和服务人员； （六）具有安全可靠的脐带血来源保证； （七）具备多渠道筹集建设资金运转经费的能力。 第九条设置脐带血造血干细胞库应向所在地省级卫生行政部门提交设置可行性研究报告，内容包括：
with用法归纳 （1）“用……”表示使用工具，手段等。例如： ①We can walk with our legs and feet. 我们用腿脚行走。 ②He writes with a pencil. 他用铅笔写。 （2）“和……在一起”，表示伴随。例如： ①Can you go to a movie with me? 你能和我一起去看电影'>电影吗？ ②He often goes to the library with Jenny. 他常和詹妮一起去图书馆。 （3）“与……”。例如： I’d like to have a talk with you. 我很想和你说句话。 （4）“关于，对于”，表示一种关系或适应范围。例如： What’s wrong with your watch? 你的手表怎么了？ （5）“带有，具有”。例如： ①He’s a tall kid with short hair. 他是个长着一头短发的高个子小孩。 ②They have no money with them. 他们没带钱。 （6）“在……方面”。例如： Kate helps me with my English. 凯特帮我学英语。 （7）“随着，与……同时”。例如： With these words, he left the room. 说完这些话，他离开了房间。 [解题过程] with结构也称为with复合结构。是由with+复合宾语组成。常在句中做状语，表示谓语动作发生的伴随情况、时间、原因、方式等。其构成有下列几种情形： 1.with+名词(或代词)+现在分词 此时，现在分词和前面的名词或代词是逻辑上的主谓关系。 例如:1)With prices going up so fast, we can't afford luxuries. 由于物价上涨很快，我们买不起高档商品。（原因状语） 2)With the crowds cheering, they drove to the palace. 在人群的欢呼声中，他们驱车来到皇宫。（伴随情况） 2.with+名词(或代词)+过去分词 此时，过去分词和前面的名词或代词是逻辑上的动宾关系。
古代汉语词类活用例句列举 古代汉语词类活用例句列举《郑伯克段于鄢》１、例：壮公生，惊姜氏。P97 惊：用作使动，使。。。惊。２、例：无生民心。P99 生：用作使动，使。。。产生。３、例：若阙地及泉，隧而相见。P101 隧：名词动用。《公孙无知之乱》４、豕立而啼，P109 立：名词作状语，像人一样丫立。〈安之战〉５、皆主？献子。P117 主：名词动用，以。。。为主。６、君无所辱命。P119 辱：动词使动，使。。。受辱。７、从左右，皆肘之。P123 肘：名词使动，表示用胳膊推撞。８、臣辱戎士。123 辱：动词使动。９、人不难以死免其君。P123 免：用作使动，使。。。免于。１０、故中御而从齐候。P123 中：方位名词做状语。〈子产说范宣子轻敝〉１１、三周华不注。P122 周：
名词动用。１２、郑人病之。P129 病：名词用作意动。１３、象有齿而焚其身。P130 焚：动词用作使动。１４、宣子说，乃轻弊。P130 轻：形容词用作使动，使。。。轻。〈苏秦连横约纵〉１５、今先生俨然不运千里而庭教之。P182 远：形容词用作意动。１６、明言章理，兵甲愈起。P183 明、章：用作使动。 1 １７、辨言伟服。攻战不息。P183 辩、伟：都用作使动，使。。。雄辩，使。。。华美。１８、繁称文辞，天下不冶。P183 文：名词用作使动。１９、夫徒处而致利，安坐而广地。P183 广：形容词用作使动，使。。。广。２０、言语相结，天下为一。P183 言语：名词作状语。２１、今欲并天下，凌万乘，诎敌国。制海内，子元元。臣诸候。非兵不可。P183 诎：用作使动，使。。。屈服；子：名词用作使动，使。。。成为子女；臣：名词用作使动，使。。。成为臣子。２２、约纵散横，以抑强秦。
独立主格篇 独立主格，首先它是一个“格”，而不是一个“句子”。在英语中任何一个句子都要有主谓结构，而在这个结构中，没有真正的主语和谓语动词，但又在逻辑上构成主谓或主表关系。独立主格结构主要用于描绘性文字中，其作用相当于一个状语从句，常用来表示时间、原因、条件、行为方式或伴随情况等。除名词/代词+名词、形容词、副词、非谓语动词及介词短语外，另有with或without短语可做独立主格，其中with可省略而without不可以。*注：独立主格结构一般放在句首，表示原因时还可放在句末；表伴随状况或补充说明时，相当于一个并列句，通常放于句末。 一、独立主格结构： 1. 名词/代词+形容词 He sat in the front row, his mouth half open. Close to the bank I saw deep pools, the water blue like the sky. 靠近岸时，我看见几汪深池塘，池水碧似蓝天。 2. 名词/代词+现在分词 Winter coming, it gets colder and colder. The rain having stopped, he went out for a walk.
The question having been settled, we wound up the meeting. 也可以The question settled, we wound up the meeting. 但含义稍有差异。前者强调了动作的先后。 We redoubled our efforts, each man working like two. 我们加倍努力，一个人干两个人的活。 3. 名词/代词+过去分词 The job finished, we went home. More time given, we should have done the job much better. *当表人体部位的词做逻辑主语时，不及物动词用现在分词，及物动词用过去分词。 He lay there, his teeth set, his hands clenched, his eyes looking straight up. 他躺在那儿，牙关紧闭，双拳紧握，两眼直视上方。 4. 名词/代词+不定式 We shall assemble at ten forty-five, the procession to start moving at precisely eleven. We divided the work, he to clean the windows and I to sweep the floor.
古代汉语练习（词类活用） 班级：姓名：学号： 一、简答： 1、什么是古代汉语的词类活用？古代汉语中的词类活用有哪几种？ 2、怎样区别使动用法和意动用法？试举例说明。并说明如何翻译。 3、试说明名词做状语主要有哪几种情况。 4、名词、形容词用作动词的情况主要有哪些？应该如何辨认？ 二、多项选择题（在每小题的四个备选答案中，选出二个至四个正确的答案，并将其号码分别填在题干后的括号内，多选、少选、错选均无分。每小题1分，共5分） 1．下列各句中加着重号的词，属于词类活用的是（） A．斩一首者爵一级B．能富贵将军者，上也 C．曹人凶俱，为其所得者棺而出之 D．夫鼠，昼伏夜动，不穴于寝庙，畏人故也 2．下列各句中加着重号的词属于名词作状语的是（） A．裂裳衣疮，手往善药 B．其经承子厚口讲指画为文词者，悉有法度可观 C．范增数目项王D．诸侯宾至 3．下列各句含宾语前置现象的是（） A．姜氏何厌之有B．楚君之惠，末之敢忘 C．除君之恶，唯力是视D．昭王南征而不复，寡人是问 4．对下列各句中加着重号的词组分析错误的是（） A．子重使太宰伯州犁待于王后（动宾）B．将塞井夷灶而为行也（连动） C．臣之壮也犹不如人（主谓）D．以勇力之所加而治智能之官（偏正） 5．下列句子中有使动用法的是（） A．秋九月，晋侯饮赵盾酒，伏甲将攻之 B．是时万石君奋为汉王中涓，受手谒，人见平
C．见灵辄饿，问其病，曰：“不食三日矣。”食之，舍其半 D．仓廪实而知礼节，衣食足而知荣辱 四、指出并具体说明下列文句中的词类活用现象： 1．秦数败赵军，赵军固壁不战。（秦与赵兵相距长平） 2．赵王不听，遂将之。（秦与赵兵相距长平） 3．身所奉饭饮而进食者以十数，所友者以百数。（秦与赵兵相距长平） 4．括军败，数十万之众遂降秦，秦悉阬之。（秦与赵兵相距长平） 5．信数与萧何语，何奇之。（韩信拜将） 6．王必欲长王汉中，无所事信。（韩信拜将） 7．吾亦欲东耳，安能郁郁久居此乎？（韩信拜将） 8．何闻信亡，不及以闻，自追之。（韩信拜将） 9．今大王举而东，三秦可传檄而定也。（韩信拜将） 10．遇有以梦得事白上者，梦得于是改刺连州。（柳子厚墓志铭） 11．自子厚之斥，遵从而家焉，逮其死不去。（柳子厚墓志铭） 12．以如司农治事堂，栖之梁木上。（段太尉逸事状） 13．踔厉风发，率常屈其座人。（柳子厚墓志铭） 14．晞一营大噪，尽甲。（段太尉逸事状） 15．即自取水洗去血，裂裳衣疮，手注善药。（段太尉逸事状） 16．黄罔之地多竹，大者如椽。竹工破之，刳去其节，用代陶瓦。（黄冈竹楼记）17．晋灵公不君。厚敛以彫墙。（晋灵公不君） 18．既而与为公介，倒戟以御公徒而免之。（晋灵公不君） 19．盛服将朝，尚早，坐而假寐。（晋灵公不君） 20．晋侯饮赵盾酒，伏甲将攻之。（晋灵公不君） 五、说明下列文句中的词类活用现象，并将全文译为现代汉语：
with用法小结 一、with表拥有某物 Mary married a man with a lot of money . 马莉嫁给了一个有着很多钱的男人。 I often dream of a big house with a nice garden . 我经常梦想有一个带花园的大房子。 The old man lived with a little dog on the lonely island . 这个老人和一条小狗住在荒岛上。 二、with表用某种工具或手段 I cut the apple with a sharp knife . 我用一把锋利的刀削平果。 Tom drew the picture with a pencil . 汤母用铅笔画画。 三、with表人与人之间的协同关系 make friends with sb talk with sb quarrel with sb struggle with sb fight with sb play with sb work with sb cooperate with sb I have been friends with Tom for ten years since we worked with each other, and I have never quarreled with him . 自从我们一起工作以来，我和汤姆已经是十年的朋友了，我们从没有吵过架。 四、with 表原因或理由 John was in bed with high fever . 约翰因发烧卧床。 He jumped up with joy . 他因高兴跳起来。 Father is often excited with wine . 父亲常因白酒变的兴奋。 五、with 表“带来”，或“带有,具有”，在…身上，在…身边之意
初中所学文言文中的五类常见词类活用现象
古代汉语中的词类活用现象 五种类型：名词用作动词 动词、形容词、名词的使动用法 形容词、名词的意动用法 名词用作状语 动词用作状语 （一）名词用如动词 古代汉语名词可以用如动词的现象相当普遍。如： 从左右，皆肘．之。（左传成公二年） 晋灵公不君．。（左传宣公二年） 孟尝君怪其疾也，衣冠 ．．而见之。（战国策·齐策四） 马童面．值，指王翳曰：“此项王也。”（史记·项羽本纪） 夫子式．而听之。（礼记·檀弓下） 曹子手．剑而从之。（公羊传庄公十三年） 假舟楫者，非能水．也，而绝江河。（荀子·劝学） 左右欲刃．相如。（史记·廉颇蔺相如列传） 秦师遂东．。（左传僖公三十二年） 汉败楚，楚以故不能过荥阳而西．。（史记·项羽本纪） 以上所举的例子可以分为两类：前八个例子是普通名词用如动词，后两个例子是方位名词用如动词。 名词用作动词是由上下文决定的。我们鉴别某一个名词是不是用如动词，须要从整个意思来考虑，同时还要注意它在句中的地位，以及它前后有哪些词类的词和它相结合，跟他构成什么样的句法关系。一般情况有如下四种：
①代词前面的名词用如动词（肘之、面之），因为代词不受名词修饰； ②副词尤其是否定副词后面的名词用如动词（“遂东”、“不君”）； ③能愿动词后面的名词也用如动词（“能水”、“欲刃”）； ④句中所确定的宾语前面的名词用如动词（“脯鄂侯”“手剑”） （二）动词、形容词、名词的使动用法 一、动词的使动用法。 定义：主语所代表的人物并不施行这个动词所表示的动作，而是使宾语所代表的人或事物施行这个动作。例如：《左传隐公元年》：“庄公寤生，惊姜氏。”这不是说庄公本人吃惊，而是说庄公使姜氏吃惊。 在古代汉语里，不及物动词常常有使动用法。不及物动词本来不带宾语，当它带有宾语时，则一定作为使动用法在使用。如： 焉用亡．郑以陪邻？《左传僖公三十年》 晋人归．楚公子榖臣与连尹襄老之尸于楚，以求知罃。（左传成公三年） 大车无輗，小车无杌，其何以行．之哉？《论语·为政》 小子鸣．鼓而攻之可也。《论语·先进》 求也退，故进．之；由也兼人，故退．之。《论语·先进》 故远人不服，则修文德以来．之。《论语·季氏》 有时候不及物动词的后面虽然不带宾语，但是从上下文的意思看，仍是使动用法。例如《论语·季氏》：“远人不服而不能来也”这个“来”字是使远人来的意思。 古代汉语及物动词用如使动的情况比较少见。及物动词本来带有宾语，在形式上和使动用法没有什么区别，区别只在意义上。使动的宾语不是动作的接受者，而是主语所代表的人物使它具有这种动作。例如《孟子·梁惠王上》“朝秦楚”，不食齐宣王朝见秦楚之君，相反的，是齐宣王是秦楚之君朝见自己。 下面各句中的及物动词是使动用法： 问其病，曰：“不食三日矣。”食．之。《左传·宣公二年》
卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规 范(试行)》的通知 【法规类别】采供血机构和血液管理 【发文字号】卫办医政发[2009]189号 【失效依据】国家卫生计生委办公厅关于印发造血干细胞移植技术管理规范(2017年版)等15个“限制临床应用”医疗技术管理规范和质量控制指标的通知 【发布部门】卫生部(已撤销) 【发布日期】2009.11.13 【实施日期】2009.11.13 【时效性】失效 【效力级别】部门规范性文件 卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规范（试行）》的通知 （卫办医政发〔2009〕189号） 各省、自治区、直辖市卫生厅局，新疆生产建设兵团卫生局： 为贯彻落实《医疗技术临床应用管理办法》，做好脐带血造血干细胞治疗技术审核和临床应用管理，保障医疗质量和医疗安全，我部组织制定了《脐带血造血干细胞治疗技术管理规范（试行）》。现印发给你们，请遵照执行。 二〇〇九年十一月十三日
脐带血造血干细胞 治疗技术管理规范（试行） 为规范脐带血造血干细胞治疗技术的临床应用，保证医疗质量和医疗安全，制定本规范。本规范为技术审核机构对医疗机构申请临床应用脐带血造血干细胞治疗技术进行技术审核的依据，是医疗机构及其医师开展脐带血造血干细胞治疗技术的最低要求。 本治疗技术管理规范适用于脐带血造血干细胞移植技术。 一、医疗机构基本要求 （一）开展脐带血造血干细胞治疗技术的医疗机构应当与其功能、任务相适应，有合法脐带血造血干细胞来源。 （二）三级综合医院、血液病医院或儿童医院，具有卫生行政部门核准登记的血液内科或儿科专业诊疗科目。 1.三级综合医院血液内科开展成人脐带血造血干细胞治疗技术的，还应当具备以下条件： （1）近3年内独立开展脐带血造血干细胞和（或）同种异基因造血干细胞移植15例以上。 （2）有4张床位以上的百级层流病房，配备病人呼叫系统、心电监护仪、电动吸引器、供氧设施。 （3）开展儿童脐带血造血干细胞治疗技术的，还应至少有1名具有副主任医师以上专业技术职务任职资格的儿科医师。 2.三级综合医院儿科开展儿童脐带血造血干细胞治疗技术的，还应当具备以下条件：
文言实词词类活用 活用为一般动词 （一）名词活用为一般动词 1.两个名词连用，既不是并列关系，又不是修饰关系，便是动宾或主谓，其中一个必然活用为动词。 a .有一老父，衣褐，至良所。 b.籍吏民，封府库。 c.我有嘉宾，鼓瑟吹笙。 d.冬雷震震夏雨雪。 2.名词后紧跟代词，该名词活用为动词。 a.驴不胜怒，蹄之。 b.以其乃华山之阳名之。 c.名余曰正则兮。 3.名词放在副词后，便活用为动词。 a.日将暮，取儿槁葬。 b.太子及宾客知其事者，皆白衣冠以送之。 c.从弟子女十人所，皆衣缯单衣，立大巫后。 4.名词放在“能”“可”“足”“欲”等呢过愿动词后，便活用为动词。 a.假舟楫者，非能水也。 b.云青青兮欲雨。 c.其力尚足以入，火尚足以明。 d.子谓公冶长：“可妻也。” 5.名词带介宾结构做补语，这个名词活用为动词。 a.晋军（于）函陵，秦军（于）氾南。 b.唐浮图慧褒始舍于其址。 6.名词用“而”同动词或动宾词组连接时，活用为动词。 a.三代不同礼而王，五霸不同法而霸。 7.名词在“所”“者”结构中便活用为动词。 a.置人所罾鱼腹中。
a.是以，令吏人完客所馆。 形容词活用为一般动词 1.形容词用在“所”字之后，便活用为动词。 故俗之所贵，主之所贱；吏之所卑，法之所尊也。 （认为宝贵、认为低贱、认为卑下、认为高贵） 2.形容词在能愿动词后，活用为动词。 问其深，则其好游者不能穷也。（走到尽头） 3.形容词在“之”“我”能代词前，活用为动词。 稍出近之。（靠近） 4.形容词后带介宾结构做补语，它活用为动词。 令尹子兰……率使上官大夫短屈原于顷襄王。 （诋毁） 数词活用做一般动词 六王毕，四海一。（统一） 名词做状语 一、普通名词作状语 1.表比喻 a.嫂蛇行匍匐。 b.狐鸣呼曰。 c .赢粮而景从。 d .天下云集响应。 e.常以身翼蔽沛公。 f.一狼径去，其一犬坐于前。 2.表对人的态度 a.君为我呼入，吾得兄事之。 b.人人皆得以隶使之。 3.表动作行为的处所 a.夫以秦王之威，相如廷叱之，辱其群臣廷：在朝廷上 b.童子隅坐而执烛. 隅：在墙角 4.表动作行为的工具、凭借、方式
with[wIT] prep.1.与…(在)一起，带着：Come with me. 跟我一起来吧。/ I went on holiday with my friend. 我跟我朋友一起去度假。/ Do you want to walk home with me? 你愿意和我一道走回家吗 2.(表带有或拥有)有…的，持有，随身带着：I have no money with me. 我没有带钱。/ He is a man with a hot temper. 他是一个脾气暴躁的人。/ We bought a house with a garden. 我们买了一座带花园的房子。/ China is a very large country with a long history. 中国是一个具有历史悠久的大国。3.(表方式、手段或工具)以，用：He caught the ball with his left hand. 他用左手接球。/ She wrote the letter with a pencil. 她用铅笔写那封信。4.(表材料或内容)以，用：Fill the glass with wine. 把杯子装满酒。/ The road is paved with stones. 这条路用石头铺砌。5.(表状态)在…的情况下，…地：He can read French with ease. 他能轻易地读法文。/ I finished my homework though with difficulty. 虽然有困难，我还是做完了功课。6.(表让步)尽管，虽然：With all his money, he is unhappy. 尽管他有钱，他并不快乐。/ With all his efforts, he lost the match. 虽然尽了全力，他还是输了那场比赛。7.(表条件)若是，如果：With your permission, I’ll go. 如蒙你同意我就去。8.(表原因或理由)因为，由于：He is tired with work. 他工作做累了。/ At the news we all jumped with joy. 听到这消息我们都高兴得跳了起来。9.(表时间)当…的时候，在…之后：With that remark, he left. 他说了那话就离开了。/ With daylight I hurried there to see what had happened. 天一亮我就去那儿看发生了什么事。10. (表同时或随同)与…一起，随着：The girl seemed to be growing prettier with each day. 那女孩好像长得一天比一天漂亮。11.(表伴随或附带情况)同时：I slept with the window open. 我开着窗户睡觉。/ Don’t speak with your mouth full. 不要满嘴巴食物说话。12.赞成，同意：I am with you there. 在那点上我同你意见一致。13.由…照看，交…管理，把…放在某处：I left a message for you with your secretary. 我给你留了个信儿交给你的秘书了。/ The keys are with reception. 钥匙放在接待处。14 (表连同或包含)连用，包含：The meal with wine came to ￡8 each. 那顿饭连酒每人8英镑。/ With preparation and marking a teacher works 12 hours a day. 一位老师连备课带批改作业每天工作12小时。15. (表对象或关系)对，关于，就…而言，对…来说：He is pleased with his new house. 他对他的新房子很满意。/ The teacher was very angry with him. 老师对他很生气。/ It’s the same with us students. 我们学生也是这样。16.(表对立或敌对)跟，以…为对手：The dog was fighting with the cat. 狗在同猫打架。/ He’s always arguing with his brother. 他老是跟他弟弟争论。17.(在祈使句中与副词连用)：Away with him! 带他走！/ Off with your clothes! 脱掉衣服！/ Down with your money! 交出钱来！ 【用法】1.表示方式、手段或工具等时(=以，用)，注意不要受汉语意思的影响而用错搭配，如“用英语”习惯上用in English，而不是with English。2.与某些抽象名词连用时，其作用相当于一个副词：with care=carefully 认真地/ with kindness=kindly 亲切地/ with joy=joyfully 高兴地/ with anger=angrily 生气地/ with sorrow=sorrowfully 悲伤地/ with ease=easily 容易地/ with delight=delightedly 高兴地/ with great fluency =very fluently 很流利地3.表示条件时，根据情况可与虚拟语气连用：With more money I would be able to buy it. 要是钱多一点，我就买得起了。/ With better equipment, we could have finished the job even sooner. 要是设备好些，我们完成这项工作还要快些。4.比较with 和as：两者均可表示“随着”，但前者是介词，后者是连词：He will improve as he grows older. 随着年龄的增长，他会进步的。/ People’s ideas change with the change of the times. 时代变了，人们的观念也会变化。5.介词with和to 均可表示“对”，但各自的搭配不同，注意不要受汉语意思的影响而用错，如在kind, polite, rude, good, married等形容词后通常不接介词with而接to。6.复合结构“with+宾语+宾语补足语”是一个很有用的结构，它在句中主要用作状语，表示伴随、原因、时间、条件、方式等；其中的宾语补足语可以是名词、形容词、副词、现在分词、过去分词、不定式、介词短语等：I went out with the windows open. 我外出时没有关窗户。/ He stood before his teacher with his head down. 他低着头站在老师面前。/ He was lying on the bed with all his clothes on. 他和衣躺在床上。/ He died with his daughter yet a schoolgirl. 他去世时，女儿还是个小学生。/ The old man sat there with a basket beside her. 老人坐在那儿，身边放着一个篮子。/ He fell asleep with the lamp burning. 他没熄灯就睡着了。/ He sat there with his eyes closed. 他闭目坐在那儿。/ I can’t go out with all these clothes to wash. 要洗这些衣服，我无法出去了。这类结构也常用于名词后作定语：The boy with nothing on is her son. 没穿衣服的这个男孩子是她儿子。 （摘自《英语常用词多用途词典》金盾出版社） - 1 -
卫生部关于印发《脐带血造血干细胞库设置管理规范(试行)》的通知 发文机关：卫生部(已撤销) 发布日期： 2001.01.09 生效日期： 2001.02.01 时效性：现行有效 文号：卫医发(2001)10号 各省、自治区、直辖市卫生厅局： 为贯彻实施《脐带血造血干细胞库管理办法（试行）》，保证脐带血临床使用的安全、有效，我部制定了《脐带血造血干细胞库设计管理规范（试行）》。现印发给你们，请遵照执行。 附件：《脐带血造血干细胞库设置管理规范（试行）》 二○○一年一月九日 附件： 脐带血造血干细胞库设置管理规范（试行） 脐带血造血干细胞库的设置管理必须符合本规范的规定。 一、机构设置 （一）脐带血造血干细胞库（以下简称脐带血库）实行主任负责制。 （二）部门设置 脐带血库设置业务科室至少应涵盖以下功能：脐带血采运、处理、细胞培养、组织配型、微生物、深低温冻存及融化、脐带血档案资料及独立的质量管理部分。 二、人员要求
（一）脐带血库主任应具有医学高级职称。脐带血库可设副主任，应具有临床医学或生物学中、高级职称。 （二）各部门负责人员要求 1．负责脐带血采运的人员应具有医学中专以上学历，2年以上医护工作经验，经专业培训并考核合格者。 2．负责细胞培养、组织配型、微生物、深低温冻存及融化、质量保证的人员应具有医学或相关学科本科以上学历，4年以上专业工作经历，并具有丰富的相关专业技术经验和较高的业务指导水平。 3．负责档案资料的人员应具相关专业中专以上学历，具有计算机基础知识和一定的医学知识，熟悉脐带血库的生产全过程。 4．负责其它业务工作的人员应具有相关专业大学以上学历，熟悉相关业务，具有2年以上相关专业工作经验。 （三）各部门工作人员任职条件 1．脐带血采集人员为经过严格专业培训的护士或助产士职称以上卫生专业技术人员并经考核合格者。 2．脐带血处理技术人员为医学、生物学专业大专以上学历，经培训并考核合格者。 3．脐带血冻存技术人员为大专以上学历、经培训并考核合格者。 4．脐带血库实验室技术人员为相关专业大专以上学历，经培训并考核合格者。 三、建筑和设施 （一）脐带血库建筑选址应保证周围无污染源。 （二）脐带血库建筑设施应符合国家有关规定，总体结构与装修要符合抗震、消防、安全、合理、坚固的要求。 （三）脐带血库要布局合理，建筑面积应达到至少能够储存一万份脐带血的空间；并具有脐带血处理洁净室、深低温冻存室、组织配型室、细菌检测室、病毒检测室、造血干/祖细胞检测室、流式细胞仪室、档案资料室、收/发血室、消毒室等专业房。 （四）业务工作区域应与行政区域分开。
with复合结构 一. with复合结构的常见形式 1.“with+名词/代词+介词短语”。 The man was walking on the street, with a book under his arm. 那人在街上走着，腋下夹着一本书。 2. “with+名词/代词+形容词”。 With the weather so close and stuffy, ten to one it’ll rain presently. 天气这么闷热，十之八九要下雨。 3. “with+名词/代词+副词”。 The square looks more beautiful than even with all the light on. 所有的灯亮起来，广场看起来更美。 4. “with+名词/代词+名词”。 He left home, with his wife a hopeless soul. 他走了，妻子十分伤心。 5. “with+名词/代词+done”。此结构过去分词和宾语是被动关系，表示动作已经完成。 With this problem solved, neomycin 1 is now in regular production. 随着这个问题的解决，新霉素一号现在已经正式产生。 6. “with+名词/代词+-ing分词”。此结构强调名词是-ing分词的动作的发出者或某动作、状态正在进行。 He felt more uneasy with the whole class staring at him. 全班同学看着他，他感到更不自然了。 7. “with+宾语+to do”。此结构中，不定式和宾语是被动关系，表示尚未发生的动作。 So in the afternoon, with nothing to do, I went on a round of the bookshops. 由于下午无事可做，我就去书店转了转。 二. with复合结构的句法功能 1. with 复合结构，在句中表状态或说明背景情况，常做伴随、方式、原因、条件等状语。With machinery to do all the work, they will soon have got in the crops. 由于所有的工作都是由机器进行，他们将很快收完庄稼。（原因状语） The boy always sleeps with his head on the arm. 这个孩子总是头枕着胳膊睡觉。（伴随状语）The soldier had him stand with his back to his father. 士兵要他背对着他父亲站着。（方式状语）With spring coming on, trees turn green. 春天到了，树变绿了。（时间状语） 2. with 复合结构可以作定语 Anyone with its eyes in his head can see it’s exactly like a rope. 任何一个头上长着眼睛的人都能看出它完全像一条绳子。 【高考链接】 1. ___two exams to worry about, I have to work really hard this weekend.（04北京） A. With B. Besides C. As for D. Because of 【解析】A。“with+宾语+不定式”作状语，表示原因。 2. It was a pity that the great writer died, ______his works unfinished. (04福建) A. for B. with C. from D.of 【解析】B。“with+宾语+过去分词”在句中作状语，表示状态。 3._____production up by 60%, the company has had another excellent year. (NMET) A. As B.For C. With D.Through 【解析】C。“with+宾语+副词”在句中作状语，表示程度。
词类活用例子 Company Document number：WUUT-WUUY-WBBGB-BWYTT-1982GT
文言实词词类活用 活用为一般动词 （一）名词活用为一般动词 1.两个名词连用，既不是并列关系，又不是修饰关系，便是动宾或主谓，其中一个必然活用为动词。 a .有一老父，衣褐，至良所。 b.籍吏民，封府库。 c.我有嘉宾，鼓瑟吹笙。 d.冬雷震震夏雨雪。 2.名词后紧跟代词，该名词活用为动词。 a.驴不胜怒，蹄之。 b.以其乃华山之阳名之。 c.名余曰正则兮。 3.名词放在副词后，便活用为动词。 a.日将暮，取儿槁葬。 b.太子及宾客知其事者，皆白衣冠以送之。 c.从弟子女十人所，皆衣缯单衣，立大巫后。 4.名词放在“能”“可”“足”“欲”等呢过愿动词后，便活用为动词。 a.假舟楫者，非能水也。 b.云青青兮欲雨。 c.其力尚足以入，火尚足以明。 d.子谓公冶长：“可妻也。”
5.名词带介宾结构做补语，这个名词活用为动词。 a.晋军（于）函陵，秦军（于）泛南。 b.唐浮图慧褒始舍于其址。 6.名词用“而”同动词或动宾词组连接时，活用为动词。 a.三代不同礼而王，五霸不同法而霸。 7.名词在“所”“者”结构中便活用为动词。 a.置人所罾鱼腹中。 a.是以，令吏人完客所馆。 形容词活用为一般动词 1.形容词用在“所”字之后，便活用为动词。 故俗之所贵，主之所贱；吏之所卑，法之所尊也。（认为宝贵、认为低贱、认为卑下、认为高贵）2.形容词在能愿动词后，活用为动词。 问其深，则其好游者不能穷也。（走到尽头） 3.形容词在“之”“我”能代词前，活用为动词。 稍出近之。（靠近） 4.形容词后带介宾结构做补语，它活用为动词。 令尹子兰……率使上官大夫短屈原于顷襄王。 （诋毁） 数词活用做一般动词 六王毕，四海一。（统一） 名词做状语