Publications (47)21.23 Total impact
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Article: The properties of a large volume-limited sample of face-on low surfacebrightness disk galaxies
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ABSTRACT: We select a large volume-limited sample of low surface brightness galaxies (LSBGs, 2,021) to investigate their statistical properties and their differences from high surface brightness galaxies (HSBGs, 3,639) in details. The distributions of stellar masses of LSBGs and HSBGs are nearly the same and they have the same median values. Thus this volume-limited sample have good completeness and further remove the effect of stellar masses on their other properties when we compare LSBGs and HSBGs. We found that LSBGs tend to have lower stellar metallicities, and lower effect dust attenuations indicating that they have lower dust, than HSBGs. The LSBGs have relatively higher stellar mass-to-light ratios, higher gas fraction, lower star forming rates (SFRs), and lower specific SFRs than HSBGs. Moreover, with the decreasing surface brightness, gas fraction increase, while the SFRs and specific SFRs decrease rapidly for the sample galaxies. This could mean that the star formation histories between LSBGs and HSBGs are different, HSBGs may have stronger star forming activities than LSBGs.Research in Astronomy and Astrophysics 05/2012; · 1.32 Impact Factor -
Article: Star formation histories and evolution of the 35 brightest E+A galaxies from the Sloan Digital Sky Survey Data Release 5
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ABSTRACT: For our sample, we have selected the 35 brightest galaxies from the Goto E+A galaxy catalogue, taken from the Sloan Digital Sky Survey Data Release 5. As E+A galaxies have experienced starburst recently and quenched it abruptly, these are considered as post-starburst galaxies. The spectra of E+A galaxies are prominently characterized by strong Balmer absorption lines but few [O ii] or Hα emission lines. In this paper we study the stellar populations of our E+A sample by fitting their spectra using ulyss, which is a robust full-spectrum fitting method. We fit each galaxy of the sample with one-population – a single stellar population (SSP) – and three-population (three SSPs) models, separately. Using one-population fits, we obtain SSP equivalent ages and metallicities, which correspond to ‘luminosity-weighted’ averages. Using three-population fits, we divide the stellar components of a galaxy into three groups by age: old stellar population (OSP), intermediate-age stellar population (ISP) and young stellar population (YSP). We then derive the optimal age, metallicity and population fractions in both mass and luminosity of OSP, ISP and YSP for each galaxy of the E+A sample. During the fits, both Pegase.HR/Elodie3.1 and Vazdekis/Miles are used as two independent stellar population models. The two models result in generally consistent conclusions as follows. For all of the E+A samples, YSPs (≤1 Gyr) make important contributions to the luminosity. However, the dominant contributors to the mass are OSPs. We also reconstruct the smoothing star formation history for each galaxy of the E+A sample by giving the star formation rate (SFR) versus the evolutionary age. All of the E+A samples have low SFRs in the intermediate evolutionary stage. 11 of the 35 E+A galaxies have high SFRs in the early evolutionary stage. However, another 11 have SFRs that are high during the late evolutionary stage. This might be a result of the recently occurred but abruptly truncated starburst in such galaxies. In addition, we fit the E+A sample and 34 randomly selected elliptical galaxies with two-population (two SSPs) model, which divides the stellar components of a galaxy into two groups by age (old and young components). We obtain the equivalent age of the old component for each galaxy of the E+A sample and elliptical galaxies. By comparison, the old components of E+A galaxies are statistically much younger than those of ellipticals. From the standpoint of the stellar population age, this probably provides evidence for the proposed evolutionary link from E+A galaxies to early-type galaxies (E/S0s).Monthly Notices of the Royal Astronomical Society 10/2010; 409(2):567 - 581. · 4.90 Impact Factor -
Article: The star formation histories of red and blue low surface brightness disk galaxies
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ABSTRACT: We study the star formation histories (SFH) and stellar populations of 213 red and 226 blue nearly face-on low surface brightness disk galaxies (LSBGs), which are selected from the main galaxy sample of Sloan Digital Sky Survey (SDSS) Data Release Seven (DR7). We also want to compare the stellar populations and SFH between the two groups. The sample of both red and blue LSBGs have sufficient signal-to-noise ratio in the spectral continua. We obtain their absorption-line indices (e.g. Mg_2, H\delta_A), D_n(4000) and stellar masses from the MPA/JHU catalogs to study their stellar populations and SFH. Moreover we fit their optical spectra (stellar absorption lines and continua) by using the spectral synthesis code STARLIGHT on the basis of the templates of Simple Stellar Populations (SSPs). We find that red LSBGs tend to be relatively older, higher metallicity, more massive and have higher surface mass density than blue LSBGs. The D_n(4000)-H\delta_A plane shows that perhaps red and blue LSBGs have different SFH: blue LSBGs are more likely to be experiencing a sporadic star formation events at the present day, whereas red LSBGs are more likely to form stars continuously over the past 1-2 Gyr. Moreover, the fraction of galaxies that experienced recent sporadic formation events decreases with increasing stellar mass. Furthermore, two sub-samples are defined for both red and blue LSBGs: the sub-sample within the same stellar mass range of 9.5 <= log(M_\star/M_\odot) <= 10.3, and the surface brightness limiting sub-sample with \mu_0(R) <= 20.7 mag arcsec^{-2}. They show consistent results with the total sample in the corresponding relationships, which confirm that our results to compare the blue and red LSBGs are robust. Comment: 9 pages, 7 figures, 2 tables, Accepted for publication in A&A04/2010; -
Article: A large sample of low surface brightness disc galaxies from the SDSS- II. Metallicities in surface brightness bins
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ABSTRACT: We study the spectroscopic properties of a large sample of Low Surface Brightness galaxies (LSBGs) (with B-band central surface brightness mu0(B)>22 mag arcsec^(-2)) selected from the Sloan Digital Sky Survey Data Release 4 (SDSS-DR4) main galaxy sample. A large sample of disk-dominated High Surface Brightness galaxies (HSBGs, with mu0(B)<22 mag arcsec^(-2)) are also selected for comparison simultaneously. To study them in more details, these sample galaxies are further divided into four subgroups according to mu0(B) (in units of mag arcsec^(-2)): vLSBGs (24.5-22.75),iLSBGs (22.75-22.0), iHSBGs (22.0-21.25), and vHSBGs (<21.25). The diagnostic diagram from spectral emission-line ratios shows that the AGN fractions of all the four subgroups are small (<9%). The 21,032 star-forming galaxies with good quality spectroscopic observations are further selected for studying their dust extinction, strong-line ratios, metallicities and stellar mass-metallicities relations. The vLSBGs have lower extinction values and have less metal-rich and massive galaxies than the other subgroups. The oxygen abundances of our LSBGs are not as low as those of the HII regions in LSBGs studied in literature, which could be because our samples are more luminous, and because of the different metallicity calibrations used. We find a correlation between 12+log(O/H) and mu0(B) for vLSBGs, iLSBGs and iHSBGs but show that this could be a result of correlation between mu0(B) and stellar mass and the well-known mass-metallicity relation. This large sample shows that LSBGs span a wide range in metallicity and stellar mass, and they lie nearly on the stellar mass vs. metallicity and N/O vs. O/H relations of normal galaxies. This suggests that LSBGs and HSBGs have not had dramatically different star formation and chemical enrichment histories. Comment: 14 pages, 11 figures, accepted for publication in MNRASMonthly Notices of the Royal Astronomical Society 04/2010; · 4.90 Impact Factor -
Article: Comparing six evolutionary population synthesis models through spectral synthesis on galaxies
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ABSTRACT: We compare six popularly used evolutionary population synthesis (EPS) models (BC03, CB07, Ma05, GALEV, GRASIL, Vazdekis/Miles) through fitting the full optical spectra of six representative types of galaxies (star-forming and composite galaxies, Seyfert 2s, LINERs, E+A and early-type galaxies), which are taken from the Sloan Digital Sky Survey (SDSS). Throughout our paper, we use the simple stellar populations (SSPs) from each EPS model and the software STARLIGHT to do our fits. Our main results are: Using different EPS models the resulted numerical values of contributed light fractions change obviously, even though the dominant populations are consistent. The stellar population synthesis does depend on the selection of age and metallicity, while it does not depend on the stellar evolution track much. The importance of young populations decreases from star-forming, composite, Seyfert 2, LINER to early-type galaxies, and E+A galaxies lie between composite galaxies and Seyfert 2s in most cases. We conclude that different EPS models do derive different stellar populations, so that it is not reasonable to directly compare stellar populations estimated from different EPS models. To get reliable results, we should use the same EPS model for the compared samples. Comment: 13 pages, 4 figures, accepted for publication in A&A02/2010; -
Article: The properties of a large sample of low surface brightness galaxies from SDSS
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ABSTRACT: A large sample of low surface brightness (LSB) disk galaxies is selected from SDSS with B-band central surface brightness mu_0(B) from 22 to 24.5 mag arcsec^(-2). Some of their properties are studied, such as magnitudes, surface brightness, scalelengths, colors, metallicities, stellar populations, stellar masses and multiwavelength SEDs from UV to IR etc. These properties of LSB galaxies have been compared with those of the galaxies with higher surface brightnesses. Then we check the variations of these properties following surface brightness. Comment: 4 pages, 2 figures, to appear in proceedings of IAU symposium 262, Stellar Populations: Planning for the Next Decade, eds. G. Bruzual & S. Charlot10/2009; -
Article: Stellar population analysis on local infrared-selected galaxies
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ABSTRACT: To study the stellar population of local infrared galaxies, which contain star-forming galaxies, composite galaxies, LINERs, and Seyfert 2s. We also want to find whether infrared luminosity and spectral class have any effects on their stellar populations. The sample galaxies are selected from the main galaxy sample of SDSS-DR4 and then cross-correlated with the IRAS-PSCz catalog. We fit our spectra (stellar absorption lines and continua) using the spectral synthesis code STARLIGHT on the base of the templates of Simple Stellar Population and the spectra of star clusters.Among the 4 spectral classes, LINERs present the oldest stellar populations, and the other 3 sub-samples all present substantial young and intermediate age populations and very few old populations. The importance of young populations decreases from star-forming, composite, Seyfert 2 to LINER. As to different infrared luminosity bins, ULIGs & LIGs (log($L_{IR}/L_{\odot})\geq$11) present younger populations than starbursts and normal galaxies. However, the dominant contributors to mass are old populations in all sample galaxies. The fittings by using the spectra of star clusters with different ages and metallicities as templates also give consistent results. The dominated populations in star-forming and composite galaxies are those with metallicity $Z=0.2Z_\odot$, while LINERs and Seyfert 2s are more metal-rich. The normal galaxies are more metal-rich than the ULIGs & LIGs and starbursts for the star-forming galaxies within different infrared luminosity bins. Additionally, we also compare some synthesis results with other parameters obtained from the MPA/JHU catalog.12/2008; -
Article: A large sample of low surface brightness disc galaxies from the SDSS – I. The sample and the stellar populations
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ABSTRACT: We present the properties of a large sample (12 282) of nearly face-on low surface brightness (LSB) disc galaxies selected from the main galaxy sample of SDSS-DR4. These properties include B-band central surface brightness μ0(B), scalelengths h, integrated magnitudes, colours and distances D. This sample has μ0(B) values from 22 to 24.5 mag arcsec−2 with a median value of 22.42 mag arcsec−2, and disc scalelengths ranging from 2 to 19 kpc. They are quite bright with MB taking values from −18 to −23 mag with a median value of −20.08 mag. There exist clear correlations between log h and MB, log h and log D, log D and MB. However, no obvious correlations are found between μ0(B) and log h, colours, etc. The correlation between colours and log h is weak even though it exists. Both the optical–optical and optical–NIR colour–colour diagrams indicate that most of them have a mixture of young and old stellar populations. They also satisfy colour–magnitude relations, which indicate that brighter galaxies tend generally to be redder. The comparison between the LSBGs and a control sample of nearly face-on disc galaxies with higher surface brightness (HSB) with μ0(B) from 18.5 to 22 mag arcsec−2 show that, at a given luminosity or distance, the observed LSB galaxies tend to have larger scalelengths. These trends could be seen gradually by dividing both the LSBGs and HSBGs into two subgroups according to surface brightness. A volume-limited subsample was extracted to check the incompleteness of surface brightness. The only one of the property relations having an obvious change is the relation of log h versus μ0(B), which shows a correlation in this subsample.Monthly Notices of the Royal Astronomical Society 11/2008; 391(2):986 - 999. · 4.90 Impact Factor -
Article: Images IV: Strong evolution of the oxygen abundance in gaseous phases of intermediate mass galaxies since z=0.8
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ABSTRACT: Intermediate mass galaxies (logM(Msun)>10) at z~0.6 are the likeliest progenitors of the present-day numerous population of spirals. There is growing evidence that they have evolved rapidly since the last 6 to 8 Gyr ago, and likely have formed a significant fraction of their stellar mass, often showing perturbed morphologies and kinematics. We have gathered a representative sample of 88 such galaxies and have provided robust estimates of their gas phase metallicity. For doing so, we have used moderate spectral resolution spectroscopy at VLT/FORS2 with unprecedented high S/N allowing to remove biases coming from interstellar absorption lines and extinction to establish robust values of R23=([OII]3727 + [OIII]4959,5007)/Hbeta. We definitively confirm that the predominant population of z~0.6 starbursts and luminous IR galaxies (LIRGs) are on average, two times less metal rich than the local galaxies at a given stellar mass. We do find that the metal abundance of the gaseous phase of galaxies is evolving linearly with time, from z=1 to z=0 and after comparing with other studies, from z=3 to z=0. Combining our results with the reported evolution of the Tully Fisher relation, we do find that such an evolution requires that ~30% of the stellar mass of local galaxies have been formed through an external supply of gas, thus excluding the close box model. Distant starbursts & LIRGs have properties (metal abundance, star formation efficiency & morphologies) similar to those of local LIRGs. Their underlying physics is likely dominated by gas infall probably through merging or interactions. Our study further supports the rapid evolution of z~0.4-1 galaxies. Gas exchanges between galaxies is likely the main cause of this evolution. Comment: 21 pages, 12 figures, A&A, In press10/2008; -
Conference Proceeding: Evolution of the Mass-Metallicity Relation from IMAGES
Pathways Through an Eclectic Universe; 06/2008 -
Article: IMAGES II. A surprisingly low fraction of undisturbed rotating spiral disks at z~0.6: The morpho-kinematical relation 6 Gyrs ago
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ABSTRACT: We present a first combined analysis of the morphological and dynamical properties for the Intermediate MAss Galaxy Evolution Sequence (IMAGES) sample. It is a representative sample of 52 z~0.6 galaxies with Mstell from 1.5 to 15 10^10Msun and possessing 3D resolved kinematics and HST deep imaging in at least two broad band filters. We aim at evaluate robustly the evolution of rotating spirals since z~0.6, as well as to test the different schemes for classifying galaxies morphologically. We used all the information provided by multi-band images, color maps and 2 dimensional light fitting to assign to each object a morphological class. We divided our sample between spiral disks, peculiar objects, compact objects and mergers. Using our morphological classification scheme, 4/5 of identified spirals are rotating disks and more than 4/5 of identified peculiar galaxies show complex kinematics, while automatic classification methods such as Concentration-Asymmetry and GINI-M20 severely overestimate the fraction of relaxed disk galaxies. Using this methodology, we find that the fraction of rotating spirals has increased by a factor ~ 2 during the last 6 Gyrs, a much higher fraction that found previously based on morphologies alone. These rotating spiral disks are forming stars very rapidly, doubling their stellar masses over the last 6 Gyrs, while most of their stars have been formed few Gyrs earlier, which reveals the presence of a large gas supply. Because they are likely the progenitors of local spirals, we can conjecture how their properties are evolving. Their disks show some evidence for an inside-out growth and the gas supply/accretion is not made randomly as the disk need to be stable in order to match the local disk properties. Comment: Typos corrected, reference added03/2008; -
Article: IMAGES I. Strong evolution of galaxy kinematics since z=1
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ABSTRACT: (abbreviated) We present the first results of the ESO large program, ``IMAGES'' which aims at obtaining robust measurements of the kinematics of distant galaxies using the multi-IFU mode of GIRAFFE on the VLT. 3D spectroscopy is essential to robustly measure the often distorted kinematics of distant galaxies (e.g., Flores et al. 2006). We derive the velocity fields and $\sigma$-maps of 36 galaxies at 0.4<z<0.75 from the kinematics of the [OII] emission line doublet, and generate a robust technique to identify the nature of the velocity fields based on the pixels of the highest signal-to-noise ratios (S/N). We have gathered a unique sample of 63 velocity fields of emission line galaxies (W0([OII]) > 15 A) at z=0.4-0.75, which are a representative subsample of the population of M_stellar>1.5x10^{10} M_sun emission line galaxies in this redshift range, and are largely unaffected by cosmic variance. Taking into account all galaxies -with or without emission lines- in that redshift range, we find that at least 41+/-7% of them have anomalous kinematics, i.e., they are not dynamically relaxed. This includes 26+/-7% of distant galaxies with complex kinematics, i.e., they are not simply pressure or rotationally supported. Our result implies that galaxy kinematics are among the most rapidly evolving properties, because locally, only a few percent of the galaxies in this mass range have complex kinematics. Comment: 17 pages, 6 figures, Accepted by A&A11/2007; -
Article: Low-metallicity HII regions and galaxies (Yin+, 2007)
VizieR Online Data Catalog. 09/2007; 346:20535. -
Article: Checking the reliability of equivalent width R23 for estimating metallicities of galaxies
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ABSTRACT: We verify whether the O/H abundances of galaxies can be derived from the equivalent width (EW) R23 instead of the extinction-corrected flux R23, and eventually propose a method of improving the reliability of this empirical method, which is often used for the non-flux calibrated spectra of galaxies. We select 37,173 star-forming galaxies from the SDSS-DR2, which offers a wide range of properties to test the EW method. The EW-R23 method brings with it a significant bias: for the bulk of SDSS galaxies, it may affect the determination of log(O/H) by factors ranging from -0.2 to 0.1 dex and for some galaxies by factors ranging from -0.5 to 0.2 dex. We characterize this discrepancy (or bias) by alpha = (I_[OII]/I_Hbeta)/(EW_[OII]/EW_Hbeta), which is virtually independent of dust extinction, while tightly correlating with Dn(4000), although at a lower significance, with (g-r) colors. The EW-R23 method cannot be used as a proxy for the extinction-corrected flux R23 method. From analytical third-order polynomial fits of alpha versus (g-r) colors, we have been able to correct the EW-R23 method. With this additional and easy correction, the EW-R23 method provides O/H abundance values similar to those derived from the extinction-corrected flux R23 method with an accuracy of ~0.1 dex for >92% of the SDSS galaxies. Comment: 8 pages, 7 figures, A&A in press. With some corrections suggested by the language editor08/2007; -
Article: The direct oxygen abundances of metal-rich galaxies derived from electron temperature
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ABSTRACT: We aim to derive the electron temperature Te in the gas of metal-rich star-forming galaxies, which can be obtained from their ratios of auroral lines [O II]7320,7330 to nebular lines [O II]3727, in order to establish a more robust mass-metallicity relationship, and compare the Te-based (O/H) abundances with those from empirical strong-line calibrations, such as R23. We obtained 27 spectra by stacking the spectra of several hundred (even several thousand) star-forming galaxies selected from the SDSS-DR4 in each of the 27 stellar mass bins from log(M*) ~8.0 to 10.6 (logMsun). This "stack" method sufficiently improves the signal-to-noise ratio of the auroral lines [O II]7320,7330, which allow us to reliably obtain the electron temperature t2 in the low ionization region from the ratio of [O II]7320,7330 to [O II]3727, then t3 in the high ionization region from t2 by using a relation, and then the direct (O/H) abundances from Te. The results show that the empirical R23 method will overestimate the log(O/H) by 0.2 to 0.6 dex for these moderate metal-rich galaxies. The new metal-mass relationship of the galaxies with moderate metallicities is fitted by a linear fit (12+log(O/H) =6.223+0.231*logM*) confirming that empirical methods significantly overestimate (O/H). We also derived their (N/O) abundance ratios on the basis of the Te method, which are consistent with the combination of the primary and secondary components of nitrogen. For actual use, we re-derive the relations of 12+log(O/H)(Bay) vs. logM* and 12+log(O/H)(Bay) vs. logR23 from the SDSS-DR4 data, which are a bit different from those derived from DR2. Comment: 13 pages, 12 figures, 2 tables, accepted by A&A08/2007; -
Article: SDSS J121811.0+465501.2: a new Low Surface Brightness Galaxy with low metallicity
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ABSTRACT: We serendipitously find a new nearby Low Surface Brightness (LSB) galaxy from SDSS database. We estimate oxygen abundance of its H II region SDSS J121811.0+465501.2 from electron temperature, as well as for another H II region, SDSS J135440.5+535309.6, located in irregular LSB galaxy UGC 8837. These two extragalactic H II regions were classified as stars in the SDSS-DR4 database, and were found occasionally by us in the automatic recognition and classification on stellar spectra.Their optical spectra show obvious emission lines, i.e., strong [O III]4959, 5007, Balmer emission lines, but very weak [N II]6548,6583 and [S II]6317,6731, which could indicate that they are metal-poor star-forming regions. The derived oxygen abundances of the two objects are 12+log(O/H) ~ 7.88+-0.30 and 7.70+-0.30, respectively. The host of the H II region SDSS J121811.0+465501.2 is identified as a new nearly edge-on LSB disc galaxy (almost without bulge) with the B-band central surface brightness mu_0(B) as 23.68 mag arcsec^{-2} and inclination angle as ~75 degree by using the GIM2D software to analyze its g- and r-band images independently. It is a nearby dwarf galaxy with redshift z~0.00157, disk scale-length ~0.40 kpc and B-band absolute magnitude M_B ~ -13.51 mag. The very low oxygen abundances of these two objects confirm the low metallicities of LSB galaxies.The Astronomical Journal 06/2007; · 4.03 Impact Factor -
Article: Redshift catalog of 691 objects in CDFS (Ravikumar+, 2007)
VizieR Online Data Catalog. 03/2007; 346:51099. -
Article: The dependence of some metallicity calibrations of strong-line ratios on nitrogen enrichment history
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ABSTRACT: We show the dependence of the Bayesian and the N2-derived oxygen abundances on the N-enrichment history of the star-forming galaxies. We select 531 metal-poor and ~20,000 metal-rich galaxies from the SDSS database for this study. Their "accurate" O/H abundances are obtained from Te and P-method, respectively. The discrepancies of the Bayesian and N2-derived abundances from these two "accurate" abundances show obvious correlations with log(N/O) abundance ratios.02/2007; -
Article: 531 new spectroscopic redshifts from the CDFS and a test on the cosmological relevance of the GOODS-South field
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ABSTRACT: (Abbrev.) This paper prepares a series of papers analysing the Intermediate MAss Galaxy Evolution Sequence (IMAGES) up to z=1. Intermediate mass galaxies (MJ <=-20.3) are selected from the Chandra Deep Field South (CDFS) for which we identify a serious lack of spectroscopically determined redshifts..... We have spectroscopically identified 691 objects including 580 gal., 7 QSOs, and 104 stars. This study provides 531 new redshifts in the CDFS. It confirms the presence of several large scale structures in the CDFS. To test the impact of these structures in the GOODS-South field, we ... compare the evolution of rest-frame U, B, V and K galaxy luminosity densities to that derived from the CFRS. The CDFS field shows a significant excess of luminosity densities in the z=0.5-0.75 range, which increases with the wavelength, reaching up to 0.5 dex at 2.1 um. Stellar mass and specific star formation evolutions might be significantly affected by the presence of the peculiar large scale structures at z= 0.668 and at z= 0.735, that contain a significant excess of evolved, massive galaxies when compared to other fields. This leads to a clear warning to results based on the CDFS/GOODS South fields, especially those related to the evolution of red luminosity densities, i.e. stellar mass density and specific star formation rate. Photometric redshift techniques, when applied to that field, are producing quantities which are apparently less affected by cosmic variance (0.25 dex at 2.1 um), however at the cost of the difficulty in disentangling between evolutionary and cosmic variance effects.01/2007; -
Article: Calibrating oxygen abundances for star-forming galaxies
Advances in Space Research 01/2007; 40:620-624. · 1.18 Impact Factor
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Institutions
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2008
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Chinese Academy of Sciences
Beijing, Beijing Shi, China -
Hebei Normal University
Shijiazhuang, Hebei, China
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