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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
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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&A
04/2010;
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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 MNRAS
Monthly Notices of the Royal Astronomical Society 04/2010; · 4.90 Impact Factor
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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. Charlot
10/2009;
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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
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VizieR Online Data Catalog. 09/2007; 346:20535.
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ABSTRACT: The halo structure at high Galactic latitudes near both the north and south poles is studied using SDSS and SuperCOSMOS data. For the south cap halo, the archive of the SuperCOSMOS photographic photometry sky survey is used. The coincident source rate between SuperCOSMOS data in $B_J$ band from $16^m.5$ to $20^m.5$ and SDSS data is about 92%, in a common sky area in the south. While that in the $R_F$ band is about 85% from $16^m.5$ to $19^m.5$. Transformed to the SuperCOSMOS system and downgraded to the limiting magnitudes of SuperCOSMOS, the star counts in the northern Galactic cap from SDSS show up to an $16.9\pm6.3%$ asymmetric ratio (defined as relative fluctuations over the rotational symmetry structure) in the $B_J$ band, and up to $13.5\pm6.7%$ asymmetric ratio in the $R_F$ band. From SuperCOSMOS $B_J$ and $R_F$ bands, the structure of the southern Galactic hemisphere does not show the same obvious asymmetric structures as the northern sky does in both the original and downgraded SDSS star counts. An axisymmetric halo model with n=2.8 and q=0.7 can fit the projected number density from SuperCOSMOS fairly well, with an average error of about 9.17%. By careful analysis of the difference of star counts between the downgraded SDSS northern halo data and SuperCOSMOS southern halo data, it is shown that no asymmetry can be detected in the south Galactic cap at the accuracy of SuperCOSMOS, and the Virgo overdensity is likely a foreign component in the Galactic halo.
04/2007;
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Advances in Space Research 01/2007; 40:620-624. · 1.18 Impact Factor
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ABSTRACT: We determine the gas-phase oxygen abundance for a sample of 695 galaxies and H II regions with reliable detections of [O III]4363, using the temperature-sensitive Te method. Our aims are to estimate the validity of empirical methods such as R23, R23-P, log([N II]/Halpha) (N2), log[([O III]/Hbeta)/([N II]/Halpha)] (O3N2), and log([S II]/Halpha) (S2), and especially to re-derive (or add) the calibrations of R23, N2, O3N2 and S2 indices for oxygen abundances on the basis of this large sample of galaxies with Te-based abundances. We select 531 star-forming galaxies from the SDSS-DR4, and 164 galaxies and H II regions from literature for such study. Their (O/H) abundances obtained from Te are within 7.1<12+log(O/H)<8.5 mostly. For roughly half of the SDSS samples, the Bayesian abundances obtained by the MPA/JHU group are overestimated by ~0.34 dex compared with the Te-based (O/H) measurements, possibly due to the treatment of nitrogen enrichment in the models they used. R23 and R23-P methods systematically overestimate the O/H abundance by a factor of ~0.20 dex and ~0.06 dex, respectively. The N2 index, rather than the O3N2 index, provides relatively consistent O/H abundances with the Te-method, but with some scatter. The relations of N2, O3N2, S2 with log(O/H) are consistent with the photoionization model calculations of Kewley & Doptita (2002), but R23 does not match well. Then we derive analytical calibrations for O/H from R23, N2, O3N2 and S2 indices on the basis of this large sample of galaxies, especially including the excitation parameter P as an additional parameter in the N2 calibration. These can be used as calibration references in the future studies about metallicities of galaxies. Comment: 12 pages, 8 figures, 1 table. A&A in press (Table 1 will only be published in electronic format, and can be found in the source .tar.gz file as table1.tex)
10/2006;
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ABSTRACT: Using a large sample of 38,478 star-forming galaxies selected from the Second
Data Release of the Sloan Digital Sky Survey database (SDSS-DR2), we derive
analytical calibrations for oxygen abundances from several
metallicity-sensitive emission-line ratios: [N II]/H_alpha, [O III]/[N II], [N
II]/[O II], [N II]/[S II], [S II]/H_alpha, and [O III]/H_beta. This consistent
set of strong-line oxygen abundance calibrations will be useful for future
abundance studies. Among these calibrations, [N II]/[O II] is the best for
metal-rich galaxies due to its independence on ionization parameter and low
scatter. Dust extinction must be considered properly at first. These
calibrations are more suitable for metal-rich galaxies (8.4<12+log(O/H)<9.3),
and for the nuclear regions of galaxies. The observed relations are consistent
with those expected from the photoionization models of Kewley & Dopita (2002).
However, most of the observational data spread in a range of ionization
parameter q from 1*10^7 to 8*10^7 cm s^{-1}, corresponding to logU= -3.5 to
-2.5, narrower than that suggested by the models. We also estimate the (N/O)
abundance ratios of this large sample of galaxies, and these are consistent
with the combination of a "primary" and a dominant "secondary" components of
nitrogen.
07/2006;
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ABSTRACT: Using the stellar photometry catalogue based on the latest data release (DR4) of the Sloan Digital Sky Survey (SDSS), a study of the Galactic structure using star counts is carried out for selected areas of the sky. The sample areas are selected along a circle at a Galactic latitude of +60$^\circ$, and 10 strips of high Galactic latitude along different longitudes. Direct statistics of the data show that the surface densities of $\ell$ from $180^{\circ}$ to $360^{\circ}$ are systematically higher than those of $\ell$ from $0^{\circ}$ to $180^{\circ}$, defining a region of overdensity (in the direction of Virgo) and another one of underdensity (in the direction of Ursa Major) with respect to an axisymmetric model. It is shown by comparing the results from star counts in the $(g-r)$ colour that the density deviations are due to an asymmetry of the stellar density in the halo. Theoretical models for the surface density profile are built and star counts are performed using a triaxial halo of which the parameters are constrained by observational data. Two possible reasons for the asymmetric structure are discussed. Comment: 17 pages, 7 figures, 5 tables, MNRAS accepted
02/2006;
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36th COSPAR Scientific Assembly; 01/2006
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ABSTRACT: We report the multiwavelength observations of one intermediate redshift (z=0.3884) galaxy in the Marano Field. These data include ISOCAM middle infrared, VLT/FORS2 spectroscopic and photometric data, associated with the ATCA 1.4 GHz radio and ROSAT PSPC X-ray observations from literature. The Spectral Energy Distribution obtained by VLT spectroscopy exhibits its early-type galaxy property, while, in the same time, it has obvious [OIII]5007 emission line. The diagnostic diagram from the optical emission line ratios shows its Seyfert galaxy property. Its infrared-radio relation follows the correlation of sources detected at 15 \mu and radio. It has a high X-ray luminosity of 1.26*10^{43} ergs/s, which is much higher than the general elliptical galaxies s with the similar B band luminosity, and is about 2 orders of magnitude higher than the derived value from the star forming tracer, the FIR luminosity. This means that the X-ray sources of this galaxy are not stellar components, but the AGN is the dominant component.
10/2005;
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IAU Colloq. 199: Probing Galaxies through Quasar Absorption Lines; 03/2005
