scholarly journals The Evolution of the Mass–Metallicity Relation in Seyferts

2009 ◽  
Vol 5 (S267) ◽  
pp. 144-144
Author(s):  
N. Vale Asari ◽  
G. Stasińska ◽  
R. Cid Fernandes ◽  
J. M. Gomes ◽  
M. Schlickmann ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
Empirical Relation ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Chemical Enrichment ◽  
Sky Survey ◽  
History Of

Various studies have shown that there is an empirical relation between the nebular metallicity of a galaxy and its stellar mass. Until now, most studies of the mass-metallicity relation (M–Z) have focused on the abundances of the interstellar medium as measured by emission-line features. This technique thus excludes galaxies with AGN from the working samples, due to the difficulty to measure the nebular abundances when emission-lines are powered both by stars and AGN. With our synthesis code starlight, we are able to recover the stellar metallicities of galaxies from the Sloan Digital Sky Survey (SDSS). Therefore, although we still cannot measure the nebular metallicity in AGN hosts, we know their present-day stellar metallicities. Moreover, because we measure the metallicity of stellar populations of different ages in a galaxy, we are also able also recover the history of its chemical enrichment.

scholarly journals The weak imprint of environment on the stellar populations of galaxies

2020 ◽  
Vol 500 (4) ◽  
pp. 4469-4490 ◽  
Author(s):  
James Trussler ◽  
Roberto Maiolino ◽  
Claudia Maraston ◽  
Yingjie Peng ◽  
Daniel Thomas ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Unique Feature ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey ◽  
Satellite Galaxies ◽  
Projected Distance ◽  
Environmental Dependence

ABSTRACT We investigate the environmental dependence of the stellar populations of galaxies in Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley, and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley, and passive galaxies when the environmental dependence of galaxy properties are investigated. We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly (<0.05 and <0.08 dex, respectively) with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (‘strangulation’) contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass–stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass (∼0.1 dex) at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias.

scholarly journals Quasi-stellar objects acting as potential strong gravitational lenses in the SDSS-III BOSS survey

2019 ◽  
Vol 625 ◽  
pp. A56 ◽  
Author(s):  
Romain A. Meyer ◽  
Timothée Delubac ◽  
Jean-Paul Kneib ◽  
Frédéric Courbin
Keyword(s):  
Emission Line ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Gravitational Lenses ◽  
Stellar Objects ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
Unique Approach ◽  
Algorithmic Search ◽  
Emission Line Galaxies

We present a sample of 12 quasi-stellar objects (QSOs) that potentially act as strong gravitational lenses on background emission line galaxies (ELG) or Lyman-α emitters (LAEs) selected through a systematic search of the 297 301 QSOs in the Sloan Digital Sky Survey (SDSS)-III Data Release 12. Candidates were identified by looking for compound spectra, where emission lines at a redshift larger than that of the quasar can be identified in the residuals after a QSO spectral template is subtracted from the observed spectra. The narrow diameter of BOSS fibers (2″) then ensures that the object responsible for the additional emission lines must lie close to the line of sight of the QSO and hence provides a high probability of lensing. Among the 12 candidates identified, nine have definite evidence for the presence of a background ELG identified by at least four higher-redshift nebular emission lines. The remaining three probable candidates present a strong asymmetrical emission line attributed to a background Lyman-α emitter (LAE). The QSO-ELG (QSO-LAE) lens candidates have QSO lens redshifts in the range 0.24 ≲ zQSO ≲ 0.66 (0.75 ≲ zQSO ≲ 1.23 ) and background galaxy redshifts in the range 0.48 ≲ zS, ELG ≲ 0.94 (2.17 ≲ zS, LAE ≲ 4.48). We show that the algorithmic search is complete at > 90% for QSO-ELG systems, whereas it falls at 40−60% for QSO-LAE, depending on the redshift of the source. Upon confirmation of the lensing nature of the systems, this sample may quadruple the number of known QSOs acting as strong lenses. We have determined the completeness of our search, which allows future studies to compute lensing probabilities of galaxies by QSOs and differentiate between different QSO models. Future imaging of the full sample and lens modelling offers a unique approach to study and constrain key properties of QSOs.

scholarly journals Stellar populations in star forming galaxies in the Sloan Digital Sky Survey

2009 ◽  
Vol 5 (S262) ◽  
pp. 446-447
Author(s):  
Pieter Westera ◽  
François Cuisinier ◽  
Carlos R. Rabaça
Keyword(s):  
Population Analysis ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
High Mass ◽  
Synthesis Methods ◽  
Young Generation ◽  
Homogeneous Sample ◽  
Star Forming ◽  
Sky Survey

AbstractWe examine the star forming phenomenon as it can be encountered in galaxies in the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of star forming galaxy spectra to date.After eliminating all spectra with an insufficient signal-to-noise ratio, without strong emission lines, and without the [OII] λ3727 Å line, which is necessary for the determination of the gas metallicity (which excludes galaxies with redshift ≲ 0.024–0.025), our sample contains ~6000 spectra of star forming galaxies.Through a detailed stellar population analysis employing evolutionary synthesis methods we determined the stellar composition of these galaxies, that is, the masses, ages and metallicities of their partial stellar populations.We find that most, possibly all, galaxies of our sample contain, apart from the presently bursting, ionising young generation (≤ 107 yrs), old (≥ 109 yrs) and intermediate (between 107 and 109 yrs) populations, whereas the old population dominates the stellar mass (but not the light).We also find that high (stellar) mass galaxies have higher gas metallicities and lower present star formation rates relative to their total (stellar) masses, than low mass galaxies, indicating a higher chemical evolution degree for high mass galaxies.Furthermore, we find that gas enrichment mechanisms in star forming galaxies do not vary with galactic mass, being the same for low- and high-mass galaxies on average. Gas enrichment mechanisms seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history for high-mass galaxies.

scholarly journals A quasar hiding behind two dusty absorbers

2018 ◽  
Vol 615 ◽  
pp. A43 ◽  
Author(s):  
K. E. Heintz ◽  
J. P. U. Fynbo ◽  
C. Ledoux ◽  
P. Jakobsson ◽  
P. Møller ◽  
...  
Keyword(s):  
Equivalent Width ◽  
Column Density ◽  
Gamma Ray ◽  
Empirical Relation ◽  
Sloan Digital Sky Survey ◽  
Chemical Enrichment ◽  
Sky Survey ◽  
High Metal ◽  
Color Excess ◽  
Selection Of

The cosmic chemical enrichment as measured from damped Lyα absorbers (DLAs) will be underestimated if dusty and metal-rich absorbers have evaded identification. Here we report the discovery and present the spectroscopic observations of a quasar, KV-RQ 1500–0031, at z = 2.520 reddened by a likely dusty DLA at z = 2.428 and a strong Mg II absorber at z = 1.603. This quasar was identified as part of the KiDS-VIKING Red Quasar (KV-RQ) survey, specifically aimed at targeting dusty absorbers which may cause the background quasars to escape the optical selection of e.g. the Sloan Digital Sky Survey (SDSS) quasar sample. For the DLA we find an H I column density of logN(H I) = 21.2 ± 0.1 and a metallicity of [X/H] = − 0.90 ± 0.20 derived from an empirical relation based on the equivalent width of Si IIλ 1526. We observe a total visual extinction of AV = 0.16 mag induced by both absorbers. To put this case into context we compile a sample of 17 additional dusty (AV > 0.1 mag) DLAs toward quasars (QSO-DLAs) from the literature for which we characterize the overall properties, specifically in terms of H I column density, metallicity and dust properties. From this sample we also estimate a correction factor to the overall DLA metallicity budget as a function of the fractional contribution of dusty QSO-DLAs to the bulk of the known QSO-DLA population. We demonstrate that the dusty QSO-DLAs have high metal column densities (logN(H I) + [X/H]) and are more similar to gamma-ray burst (GRB)-selected DLAs (GRB-DLAs) than regular QSO-DLAs. We evaluate the effect of dust reddening in DLAs as well as illustrate how the induced color excess of the underlying quasars can be significant (up to ~1 mag in various optical bands), even for low to moderate extinction values (AV ≲ 0.6 mag). Finally we discuss the direct and indirect implications of a significant dust bias in both QSO- and GRB-DLA samples.

Alternative classification diagrams for AGN-starburst galaxies

2019 ◽  
Vol 15 (S359) ◽  
pp. 415-417
Author(s):  
Catarina P. Aydar ◽  
J. E. Steiner ◽  
Oli Dors
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Starburst Galaxies ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Single Object ◽  
Sky Survey ◽  
Using Data ◽  
Starburst Regions

AbstractThe aim of diagnostic diagrams is to classify galactic nuclei according to their photoionizing source using emission-line ratios, differentiating starburst regions from active galactic nuclei (AGN). However, the three traditional diagnostic diagrams can sometimes be ambiguous with regard to a single object. The main goal of the present work is to propose alternative diagnostic diagrams by using distinct combinations of emission lines ratios. We present these diagrams using data from the Sloan Digital Sky Survey. With these new diagrams, it is possible to better distinguish the ionizing source in nuclei of galaxies and also to study the parameters that are relevant when considering both kinds of objects, starbursts and AGN.

scholarly journals Beware of Fake AGNs

2009 ◽  
Vol 5 (S267) ◽  
pp. 141-141
Author(s):  
G. Stasińska ◽  
N. Vale Asari ◽  
R. Cid Fernandes
Keyword(s):  
Emission Line ◽  
White Dwarfs ◽  
Stellar Populations ◽  
Sloan Digital Sky Survey ◽  
Right Wing ◽  
Agb Stars ◽  
Sky Survey ◽  
Emission Line Galaxies ◽  
The Right

AbstractIn the BPT diagram, the distribution of the emission-line galaxies from the Sloan Digital Sky Survey (SDSS) evokes the wings of a seagull. Traditionally, galaxies in the right wing are considered to host AGNs. Our study of the stellar populations of SDSS galaxies showed that ~ 1/4 of galaxies thought to host LINERs are in fact “retired galaxies,” i.e., galaxies that stopped forming stars and are ionized by hot post-AGB stars and white dwarfs (Stasińska et al. 2008). When galaxies that lack some of the lines needed to place them in the BPT diagram are included, the fraction of retired galaxies is even larger (Cid Fernandes et al., these proceedings).

scholarly journals THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: AN INVESTIGATION OF BIASES IN C iv EMISSION LINE PROPERTIES

2016 ◽  
Vol 224 (2) ◽  
pp. 14 ◽  
Author(s):  
K. D. Denney ◽  
Keith Horne ◽  
Yue Shen ◽  
W. N. Brandt ◽  
Luis C. Ho ◽  
...  
Keyword(s):  
Emission Line ◽  
Sloan Digital Sky Survey ◽  
Reverberation Mapping ◽  
Sky Survey
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