Multi-wavelength observations of SDSS J105621.45+313822.1, a broad-line, low-metallicity AGN
Jenna M. Cann, Shobita Satyapal, Thomas Bohn, Remington O. Sexton, Ryan W. Pfeifle, Christina Manzano-King, Gabriela Canalizo, Barry Rothberg, Mario Gliozzi, Na… 展开作者
Jenna M. Cann, Shobita Satyapal, Thomas Bohn, Remington O. Sexton, Ryan W. Pfeifle, Christina Manzano-King, Gabriela Canalizo, Barry Rothberg, Mario Gliozzi, Nathan J. Secrest, Laura Blecha
In contrast to massive galaxies with Solar or super-Solar gas phase metallicities, very few Active Galactic Nuclei (AGN) are found in low-metallicity dwarf galaxies. Such a population could provide insight into the origins of supermassive black holes. Here we report near-infrared spectroscopic and X-ray observations of SDSS J105621.45+313822.1, a low-mass, low-metallicity galaxy with optical narrow line ratios consistent with star forming galaxies but a broad H$α$ line and mid-infrared colors consistent with an AGN. We detect the [Si VI] 1.96$μ$m coronal line and a broad Pa$α$ line with a FWHM of $850 \pm 25$~km~s$^{-1}$. Together with the optical broad lines and coronal lines seen in the SDSS spectrum, we confirm the presence of a highly accreting black hole with mass $(2.2 \pm 1.3) \times 10^{6}$~M$_{\odot}$, with a bolometric luminosity of $\approx10^{44}$~erg~s$^{-1}$ based on the coronal line luminosity, implying a highly accreting AGN. Chandra observations reveal a weak nuclear point source with $L_{\textrm{X,2-10 keV}} = (2.3 \pm 1.2) \times 10^{41}$~erg~s$^{-1}$, $\sim 2$ orders of magnitude lower than that predicted by the mid-infrared luminosity, suggesting that the AGN is highly obscured despite showing broad lines in the optical spectrum. The low X-ray luminosity and optical narrow line ratios of J1056+3138 highlight the limitations of commonly employed diagnostics in the hunt for AGNs in the low metallicity low mass regime.
We have obtained the mass-metallicity (M-Z) relation at different lookback times for the same set of galaxies from the Sloan Digital Sky Survey, using the stellar metallicities estimated with our spectral synthesis code STARLIGHT. We have found that this relation steepens and spans a wider range in both mass and metallicity at higher redshifts. We have modeled the time evolution of stellar metallicity with a closed-box chemical evolution model, for galaxies of different types and masses. Our results suggest that the M-Z relation for galaxies with present-day stellar masses down to 10^10 M_sun …
Aims: Interacting galaxies show a metallicity dilution compared to isolated galaxies of similar masses in the mass-metallicity space at the global scale. We investigate the spatially resolved mass-metallicity relation (MZR) of galaxy pairs in the SDSS-MaNGA survey to confirm that the local relation between the stellar mass surface density and the metallicity is consistent with the MZR at the global scale. Methods: We investigate the relationship between the stellar mass surface density and the metallicity abundance, 12+log (O/H), for star-forming spaxels belonging to 298 galaxy pairs identifie…
The gas metallicity distributions across individual galaxies and across galaxy samples can teach us much about how galaxies evolve. Massive galaxies typically possess negative metallicity gradients, and mass and metallicity are tightly correlated on local scales over wide range of galaxy masses; however, the precise origins of such trends remain elusive. Here, we employ data from SDSS-IV MaNGA to explore how gas metallicity depends on local stellar mass density and on galactocentric radius within individual galaxies. We also consider how the strengths of these dependencies vary across the gala…
The metallicity of local galaxies is tightly related not only to stellar mass, i.e. the mass-metallicity relation, but also to the star formation rate (SFR) through the so-called fundamental metallicity relation (FMR); more active galaxies show lower metallicities at fixed mass. Interestingly, high-z galaxies up to z~2.5 follow the same relation defined by SDSS locally. However, different shapes have been proposed for local galaxies, and the existence of a FMR and the role of the SFR has been recently questioned by some authors. In this paper we first discuss the various parametrizations of th…
In the manuscript, the composite galaxy SDSS J103911-000057 (=SDSS J1039) is reported as a better candidate of true Type-2 AGN without hidden BLRs. None broad but only narrow emission lines detected in SDSS J1039 can be well confirmed both by the F-test technique and by the expected broad emission lines with EW smaller than 13.5Å~ with 99\% confidence level. Meanwhile, a reliable AGN power law component is preferred with confidence level higher than 7sigma in SDSS J1039. Furthermore, the long-term variability of SDSS J1039 from CSS can be well described by the DRW process with intrinsic variab…
Based on SDSS g, r and SCUSS (South Galactic Cap of u-band Sky Survey) $u$ photometry, we develop a photometric calibration for estimating the stellar metallicity from $u-g$ and $g-r$ colors by using the SDSS spectra of 32,542 F- and G-type main sequence stars, which cover almost $3700$ deg$^{2}$ in the south Galactic cap. The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is $0.14$ dex when $g-r<0.4$, and $0.16$ dex when $g-r>0.4$. Due to the deeper and more accurate magnitude of SCUSS $u$ band, the estimate can be used up to the faint magnitude of…
Based on the Beijing-Arizona-Taiwan-Connecticut (BATC) and Sloan Digital Sky Survey (SDSS) photometric data, we adopt SEDs fitting Method to evaluate the metallicity distribution for \sim40,000 main-sequence stars in the Galaxy. According to the derived photometric metallicities of these sample stars, we find that the metallicity distribution shift from metal-rich to metal-poor with the increase of distance from the Galactic center. The mean metallicity is about of 1.5 \pm 0.2dex in the outer halo and 1.3 \pm 0.1 dex in the inner halo. The mean metallicity smoothly decreases from -0.4 to -0.8 …
We present a sample of low-redshift (z<0.133) candidates for extremely low-metallicity star-forming galaxies with oxygen abundances 12+logO/H<7.4 selected from the Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS). Three methods are used to derive their oxygen abundances. Among these methods two are based on strong [OII]3727, [OIII]4959, and [OIII]5007 emission lines, which we call strong-line and semi-empirical methods. These were applied for all galaxies. We have developed one of these methods, the strong-line method, in this paper. This method is specifically focused on the accu…
We present the stellar surface mass density {\it vs.} gas metallicity ($Σ_*-Z$) relation for more than 500,000 spatially-resolved star-forming resolution elements (spaxels) from a sample of 653 disk galaxies included in the SDSS IV MaNGA survey. We find a tight relation between these local properties, with higher metallicities as the surface density increases. This relation extends over three orders of magnitude in the surface mass density and a factor of four in metallicity. We show that this local relationship can simultaneously reproduce two well-known properties of disk galaxies: their glo…
In the manuscript, we discuss properties of the SDSS J1042-0018 which is a broad line AGN but mis-classified as a HII galaxy in the BPT diagram (SDSS J1042-0018 called as a mis-classified broad line AGN). The emission lines around H$α$ and around H$β$ are well described by different model functions, considering broad Balmer lines to be described by Gaussian or Lorentz functions. Different model functions lead to different determined narrow emission line fluxes, but the different narrow emission line flux ratios lead the SDSS J1042-0018 as a HII galaxy in the BPT diagram. In order to explain th…
We infer stellar metallicity and abundance ratio gradients for a sample of red galaxies in the Sloan Digital Sky Survey (SDSS) Main galaxy sample. Because this sample does not have multiple spectra at various radii in a single galaxy, we measure these gradients statistically. We separate galaxies into stellar mass bins, stack their spectra in redshift bins, and calculate the measured absorption line indices in projected annuli by differencing spectra in neighboring redshift bins. After determining the line indices, we use stellar population modeling from the EZ\_Ages software to calculate ages…
We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with medium-resolution spectroscopic values over a wide range of metal abundance. We estimate distances and metallicities for individual main-sequence stars in the multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5 - 8 kpc and |b| > 35 deg, and find that the in situ photometric metallicity distribution has a shape that matches that of the kinematical…
We present the integrated stellar mass-metallicity relation (MZR) for more than 1700 galaxies included in the integral field area SDSS-IV MaNGA survey. The spatially resolved data allow us to determine the metallicity at the same physical scale (effective radius in arcsecs, $\mathrm{R_{eff}}$ ) using a heterogeneous set of ten abundance calibrators. Besides scale factors, the shape of the MZR is similar for all calibrators, consistent with those reported previously using single-fiber and integral field spectroscopy. We compare the residuals of this relation against the star formation rate (SFR…
We use our integrated SDSS photometry for 96 globular clusters in $g$ and $z$, as well as $r$ and $i$ photometry for a subset of 56 clusters, to derive the integrated colour-metallicity relation (CMR) for Galactic globular clusters. We compare this relation to previous work, including extragalactic clusters, and examine the influence of age, present-day mass function variations, structural parameters and the morphology of the horizontal branch on the relation. Moreover, we scrutinise the scatter introduced by foreground extinction (including differential reddening) and show that the scatter in…
Tidal stripping and three-body interactions with the central supermassive black hole may eject stars from the Milky Way. These stars would comprise a set of `intragroup' stars that trace the past history of interactions in our galactic neighborhood. Using the Sloan Digital Sky Survey DR7, we identify candidate solar metallicity red giant intragroup stars using color cuts that are designed to exclude nearby M and L dwarfs. We present 677 intragroup candidates that are selected between 300 kpc and 2 Mpc, and are either the reddest intragroup candidates (M7-M10) or are L dwarfs at larger distance…
As hosts of living high-mass stars, Wolf-Rayet (WR) regions or WR galaxies are ideal objects for constraining the high-mass end of the stellar initial mass function (IMF). We construct a large sample of 910 WR galaxies/regions that cover a wide range of stellar metallicity (from Z~0.001 up to Z~0.03), by combining three catalogs of WR galaxies/regions previously selected from the SDSS and SDSS-IV/MaNGA surveys. We measure the equivalent widths of the WR blue bump at ~4650 A for each spectrum. They are compared with predictions from stellar evolutionary models Starburst99 and BPASS, with differ…
We analyze the anisotropy profile of the Milky Way's smooth, diffuse stellar halo using SDSS/SEGUE blue horizontal branch stars and SDSS/SEGUE and LAMOST K giants. These intrinsically luminous stars allow us to probe the halo to approximately 100 kpc from the Galactic center. Line-of-sight velocities, distances, metallicities, and proper motions are available for all stars via SDSS/SEGUE, LAMOST, and Gaia, and we use these data to construct a full 7D set consisting of positions, space motions, and metallicity. We remove substructure from our samples using integrals of motion based on the metho…
In this paper we use strong line calibrations of N/O and O/H in MaNGA spaxel data to explore the systematics introduced by variations in N/O on various strong-line metallicity diagnostics. We find radial variations in N/O at fixed O/H which correlate with total galaxy stellar-mass; and which can induce $\sim 40 \%$ systematic uncertainties in oxygen abundance gradients when nitrogen-dependent abundance calibrations are used. Empirically, we find that these differences are associated with variation in the local star formation efficiency, as predicted by recent chemical evolution models for gala…
We present a comparative study of the relation between the aperture-based gas-phase metallicity and three structural parameters of star-forming galaxies: mass ($\mathrm{M \equiv M_*}$), average potential ($Φ\equiv \mathrm{M_*/R_e}$) and average surface mass density ($Σ\equiv \mathrm{M_*/R_e^2}$; where $\mathrm{R_e}$ is the effective radius). We use a volume-limited sample drawn from the publicly available SDSS DR7, and base our analysis on aperture-matched sampling by selecting sets of galaxies where the SDSS fibre probes a fixed fraction of $\mathrm{R_e}$. We find that between 0.5 and 1.5 $\m…
We derive new empirical calibrations for strong-line diagnostics of gas phase metallicity in local star forming galaxies by uniformly applying the Te method over the full metallicity range probed by the Sloan Digital Sky Survey (SDSS). To measure electron temperatures at high metallicity, where the auroral lines needed are not detected in single galaxies, we stacked spectra of more than 110,000 galaxies from the SDSS in bins of log[O II]/H$β$ and log[O III]/H$β$. This stacking scheme does not assume any dependence of metallicity on mass or star formation rate, but only that galaxies with the s…
In this Letter, we report further evidence to support a tidal disruption event (TDE) in the known changing-look AGN SDSS J0159, through the unique variabilities of asymmetric broad H$α$: broader but redder in 2010 than in 2000. Accepted the broad H$α$ emission regions tightly related to accreting debris in a central TDE, the well-known relativistic accretion disk origination can be applied to well explain the asymmetric broad H$α$ variabilities in SDSS J0159. Moreover, the model determined broad H$α$ emission regions have the sizes not follow the empirical R-L relation valid in normal broad li…
The distribution of stellar metallicities within and across galaxies is an excellent relic of the chemical evolution across cosmic time. We present a detailed analysis of spatially resolved stellar populations based on $>2.6$ million spatial bins from 7439 nearby galaxies in the SDSS-IV MaNGA survey. To account for accurate inclination corrections, we derive an equation for morphology dependent determination of galaxy inclinations. Our study goes beyond the well-known global mass-metallicity relation and radial metallicity gradients by providing a statistically sound exploration of local relat…
Aims. We focus on how to homogenize the comparison between galaxy samples having different characteristics. We check the projections of the fundamental metallicity relation (FMR) and the evolution of these projections between a sample selected at $z\sim0$ (SDSS) and $z\sim0.7$ (VIPERS). We check, in particular, whether and to what extent selection criteria can affect the results. Methods. We checked the influence of different biases introduced either by physical constraints (evolution of the luminosity function and differences in the fraction of blue galaxies) or data selection (the signal-to-…
Gas-phase metallicity gradients in galaxies provide important clues to those galaxies' formation histories. Using SDSS-IV MaNGA data, we previously demonstrated that gas metallicity gradients vary systematically and significantly across the galaxy mass--size plane: at stellar masses beyond approximately $10^{10}$ $\mathrm{M_\odot}$, more extended galaxies display steeper gradients (in units of $\mathrm{dex/R_e}$) at a given stellar mass. Here, we set out to develop a physical interpretation of these findings by examining the ability of local $\sim$kpc-scale relations to predict the gradient be…
We present a study on the stellar age and metallicity distributions for 1105 galaxies using the STARLIGHT software on MaNGA integral field spectra. We derive age and metallicity gradients by fitting straight lines to the radial profiles, and explore their correlations with total stellar mass M*, NUV-r colour and environments, as identified by both the large scale structure (LSS) type and the local density. We find that the mean age and metallicity gradients are close to zero but slightly negative, which is consistent with the inside-out formation scenario. Within our sample, we find that both …
In the Letter, an interesting method is proposed to estimate size of narrow emission lines regions (NLRs) of a Type-2 AGN SDSS J083823.91+490241.1 (=SDSS J0838) at a redshift of 0.101, by comparing spectroscopic properties through the SDSS fiber (MJD=51873) (diameter of 3 arcseconds) and through the eBOSS fiber (MJD=55277) (diameter of 2 arcseconds). After subtractions of pPXF method determined host galaxy contributions, the narrow emission lines of SDSS J0838 in the SDSS spectrum and in the eBOSS spectrum can be well measured by Gaussian functions, leading more than 90\% of [O~{\sc iii}] emis…
We have collected all available spectra and photometric data from SDSS catalogue for bright AGNs complied from the first three months of the Fermi large area telescope all-sky survey. Based on the 106 high-confidence and 11 low-confidence association bright AGN list, the photometry data are collected from SDSS DR7 for 28 sources (12 BL Lacs and 16 FSRQs), two of which are low-confidence association bright AGNs. Among these 28 SDSS photometric sources, SDSS spectra are available for 20 sources (6 BL Lacs and 14 FSRQs). The black hole mass M_BH and the broad line region (BLR) luminosity were obt…
As the third installment in a series systematically searching dual active galactic nuclei (AGN) amongst merging galaxies, we present the results of 20 dual AGNs found by using the SDSS fiber spectra. To reduce the flux contamination from both the fiber aperture and seeing effects, the angular separation of two cores in our merging galaxy pairs sample is restricted at least larger than 3 arcsec. By careful analysis of the emission lines, 20 dual AGNs are identified from 61 merging galaxies with their two cores both observed by the SDSS spectroscopic surveys. 15 of them are identified for the fi…
During galaxy merger events, the supermassive black holes in the center of the galaxies may form a pair of active galactic nuclei (AGN) with kpc-scale or even pc-scale separation. Recently, optical observations revealed a promising dual AGN candidate at the center of the galaxy SDSS J101022.95$+$141300.9 (hereafter J1010$+$1413). The presence of two distinct [O III]-emitting point sources with a projected separation of $\sim 430$ pc indicates a dual AGN system. To search for AGN-dominated radio emission originating from the Hubble Space Telescope (HST) point sources, we carried out very long b…
We study how AGN activity changes across environments from galaxy pairs to clusters using $143\, 843$ galaxies with $z<0.2$ from the Sloan Digital Sky Survey (SDSS). Using a refined technique, we apply a continuous measure of AGN activity, characteristic of the ionization state of the narrow-line emitting gas. Changes in key emission-line ratios ([NII]$\lambda6548$/H$α$, [OIII]$\lambda5007$/H$β$) between different samples allow us to disentangle different environmental effects while removing contamination. We confirm that galaxy interactions enhance AGN activity. However, conditions in the cen…
In support of ongoing projects we have compiled a database of supernovae with host metallicities determined from spectroscopy in the Sloan Digital Sky Survey (SDSS) which we are providing as a catalog for the general use of the community. Here we provide metallicity values in the KK04 (Kobulnicky & Kewley 2004), T04 (Tremonti et al. 2004), and D16 (Dopita et al. 2016) diagnostics as well as a compilation of the relevant line fluxes to allow users to compute their own metallicities. The sample presented here has approximately 1700 objects with a metallicity in at least one diagnostic, with abou…
We present Bayesian AGN Decomposition Analysis for SDSS Spectra (BADASS), an open source spectral analysis code designed for automatic detailed deconvolution of AGN and host galaxy spectra, implemented in Python, and designed for the next generation of large scale surveys. BADASS simultaneously fits all spectral components, including power-law continuum, stellar line-of-sight velocity distribution, FeII emission, as well as forbidden (narrow), permitted (broad), and outflow emission line features, all performed using Markov Chain Monte Carlo to obtain robust uncertainties and autocorrelation a…
We derive the metallicity (traced by the O/H abundance) of the Narrow Line Region ( NLR) of 108 Seyfert galaxies as well as radial metallicity gradients along their galaxy disks and of these of a matched control sample of no active galaxies. In view of that, observational data from the SDSS-IV MaNGA survey and strong emission-line calibrations taken from the literature were considered. The metallicity obtained for the NLRs %each Active Galactic Nucleus (AGN) was compared to the value derived from the extrapolation of the radial oxygen abundance gradient, obtained from \ion{H}{ii} region estima…
We examine whether galaxy environments directly affect triggering nuclear activity in Sloan Digital Sky Survey (SDSS) local spiral galaxies using a volume-limited sample with the $r$-band absolute magnitude $M_{r} < -19.0$ and $0.02 < z < 0.055$ selected from the SDSS Data Release 7. To avoid incompleteness of the central velocity dispersion $σ$ of the volume-limited sample and to fix the black hole mass affecting AGN activity, we limit the sample to a narrow $σ$ range of $130$ km s$^{-1}<σ<200$ km s$^{-1}$. We define a variety of environments as a combination of neighbour interactions and loc…
This is the first paper in a dedicated series to study the properties of the optically selected BLR-less AGNs (Active Galactic Nuclei with no-hidden central broad emission line regions). We carried out a systematic search for the BLR-less AGNs through the Sloan Digital Sky Survey Legacy Survey (SDSS Stripe82 Database). Based on the spectral decomposition results for all the 136676 spectroscopic objects (galaxies and QSOs) with redshift less than 0.35 covered by the SDSS Stripe82 region, our spectroscopic sample for the BLR-less AGNs includes 22693 pure narrow line objects without broad emissio…
We report the discovery of a kiloparsec-scale triple supermassive black hole system at $z=0.256$: SDSS J1056+5516, discovered by our systematic search for binary quasars. The system contains three strong emission-line nuclei, which are offset by $<250~{\rm km~s^{-1}}$ and by 15-18 kpc in projected separation, suggesting that the nuclei belong to the same physical structure. The system includes a tidal arm feature spanning $\sim100$ kpc in projected distance at the systems' redshift, inhabiting an ongoing or recent galaxy merger. Based on our results, such a structure can only satisfy one of th…
We study the gas phase metallicity (O/H) and nitrogen abundance gradients traced by star forming regions in a representative sample of 550 nearby galaxies in the stellar mass range $\rm 10^9-10^{11.5} M_\odot$ with resolved spectroscopic data from the SDSS-IV MaNGA survey. Using strong-line ratio diagnostics (R23 and O3N2 for metallicity and N2O2 for N/O) and referencing to the effective (half-light) radius ($\rm R_e$), we find that the metallicity gradient steepens with stellar mass, lying roughly flat among galaxies with $\rm log(M_\star/M_\odot) = 9.0$ but exhibiting slopes as steep as -0.1…
We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z <= 0.08) catalog of visually-selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2x10^10 Msun, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4]-[4.6] colors associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fiber spectral dia…
We investigate archaeologically how the metallicity in both stellar and gaseous components of spiral galaxies of differing masses evolve with time, using data from the SDSS-IV MaNGA survey. For the stellar component, we can measure this evolution directly by decomposing the galaxy absorption-line spectra into populations of different ages and determining their metallicities. For the gaseous component, we can only measure the present-day metallicity directly from emission lines. However, there is a well-established relationship between gas metallicity, stellar mass and star formation rate which…
Stellar feedback-driven outflows regulate the stellar formation and chemical enrichment of galaxies, yet the underlying dependence of mass outflow rate on galaxy properties remains largely unknown. We develop a simple yet comprehensive non-equilibrium chemical evolution model~(NE-CEM) to constrain the mass-loading factor $η$ of outflows using the metallicity-stellar mass-SFR relation observed by SDSS at $z{=}0$. Our NE-CEM predicts the chemical enrichment by explicitly tracking both the histories of star formation and mass-loading. After exploring the EAGLE simulation, we discover a compact ye…
We explore X-ray evidence for the presence of active galactic nuclei (AGNs) in the two most actively star-forming Green Pea galaxies (GPs), SDSS J0749+3337 and SDSS J0822+2241, which have star-formation rates (SFRs) of $123~M_\odot$ yr$^{-1}$ and $78~M_\odot$ yr$^{-1}$, respectively. The GPs have red mid-infrared (MIR) spectral energy distributions and higher 22 $μ$m luminosities than expected from a proxy of the SFR (H$α$ luminosity), consistent with hosting AGNs with 2-10 keV luminosities of $\sim10^{44}$ erg s$^{-1}$. We thus obtain and analyze the first hard ($>$ 10 keV) X-ray data observe…
Gaseous inflows are necessary suppliers of galaxies' star-forming fuel, but are difficult to characterize at the survey scale. We use integral-field spectroscopic measurements of gas-phase metallicity and single-dish radio measurements of total atomic gas mass to estimate the magnitude and frequency of gaseous inflows incident on star-forming galaxies. We reveal a mutual correlation between steep oxygen abundance profiles between $0.25-1.5 R_e$, increased variability of metallicity between $1.25-1.75 R_e$, and elevated HI content at fixed total galaxy stellar mass. Employing a simple but intui…
Systematic research of low redshift optically selected SDSS Type-2 AGN but with apparent long-term optical variabilities from Catalina Sky Survey, I: data sample and basic results
A large sample of MgII emitting star-forming galaxies with low metallicity [O/H] = log(O/H)-log(O/H)sun between -0.2 and -1.2 dex is constructed from Data Release 14 of the Sloan Digital Sky Survey. We selected 4189 galaxies with MgII 2797, 2803 emission lines in the redshift range z~0.3-1.0 or 35% of the total Sloan Digital Sky Survey star-forming sample with redshift z>0.3. We study the dependence of the magnesium-to-oxygen and magnesium-to-neon abundance ratios on metallicity. Extrapolating this dependence to [Mg/Ne]=0 and to solar metallicity we derive a magnesium depletion of [Mg/Ne]~-0.4…
In this manuscript, an interesting blue Active Galactic Nuclei (AGN) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H$β$ but single-peaked broad H$α$. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical co…
We investigate the relationship between host galaxies' stellar content and active galactic nuclei (AGN) for optically selected QSOs with z$<$0.5. There are total 82 QSOs we select from Sloan Digital Sky Survey (SDSS) . These 82 QSOs both have Wide-field Infrared Survey Explorer (WISE) data and measurable stellar content. With the help of the stellar population synthesis code STARLIGHT, we determine the luminosity fraction of AGN ,stellar population ages and star-formation history (SFH) of host galaxies. We find out there is a correlation between the star formation history and AGN property whic…
Gas-phase abundances and abundance gradients provide much information on past stellar generations, and are powerful probes of how galaxies evolve. Gas abundance gradients in galaxies have been studied as functions of galaxies' mass and size individually, but have largely not been considered across the galaxy mass--size plane. Thus, we investigate gas-phase abundance gradients across this plane, using a sample of over 1000 galaxies selected from the MApping Nearby Galaxies at APO (MaNGA) spectroscopic survey. We find that gradients vary systematically such that above $10^{10}M_{\odot}$, smaller…
We present a homogeneous survey of the CN and CH bandstrengths in eight Galactic globular clusters observed during the course of the Sloan Extension for Galactic Understanding and Exploration (SEGUE) sub-survey of the SDSS. We confirm the existence of a bimodal CN distribution among RGB stars in all of the clusters with metallicity greater than [Fe/H] = -1.7; the lowest metallicity cluster with an observed CN bimodality is M53, with [Fe/H] ~ -2.1. There is also some evidence for individual CN groups on the subgiant branches of M92, M2, and M13, and on the red giant branches of M92 and NGC 5053…
We measured gas-phase metallicity, ionisation parameter and dust extinction for 1795 representative local star-forming galaxies using integral field spectroscopy from the SDSS-IV MaNGA survey. We self-consistently derive these quantities by comparing observed line fluxes with photoionisation models using a Bayesian framework. We also present the first comprehensive study of the [SIII]$λλ$9069,9532 nebular lines, which have long been predicted to be ideal tracers of the ionisation parameter. Unfortunately, we find that current photoionisation models substantially over-predict [SIII] lines inten…
Environment is one of the key external drivers of the galaxies, while active galactic nucleus (AGN) is one of the key internal drivers. Both of them play fundamental roles in regulating the formation and evolution of galaxies. We explore the interrelationship between environment and AGN in SDSS. At a given stellar mass, the specific star formation rate distribution of the AGN host galaxies remains unchanged with over-density, with the peak of the distribution around the Green Valley. We show that, at a given stellar mass, the AGN fraction that has been commonly used in previous studies (define…
In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) (i) on the mid-infrared (MIR) luminosity and (ii) on the redshift. We constructed 12- and 22-micron luminosity functions (LFs) at 0.006 < z < 0.3 using the Wide-field Infrared Survey Explorer} (WISE) data. Combining the WISE catalog with the Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 micron and 25,721 galaxies at 22 micron for spectroscopic classification. We then identified 16,355 AGNs at 12 micron and 4,683 AGNs at 22 micron by their optical emi…
We present a semi-empirical calibration between the metallicity ($Z$) of Seyfert 2 Active Galactic Nuclei and the $N2$=log([N II]$λ$6584/H$α$) emission-line intensity ratio. This calibration was derived through the [O III]$λ$5007/[O II]$λ$3727 versus $N2$ diagram containing observational data and photoionization model results obtained with the Cloudy code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift $z < 0.4$) taken from the Sloan Digital Sky Survey DR7 dataset. The obtained $Z$-$N2$ relation is valid for the range $0.3 < (Z/Z_{\odot}) < 2.0$ which corresponds…
We derive ages, metallicities, and individual element abundances of early- and late-type galaxies (ETGs and LTGs) out to 1.5 R$_e$. We study a large sample of 1900 galaxies spanning $8.6 - 11.3 \log M/M_{\odot}$ in stellar mass, through key absorption features in stacked spectra from the SDSS-IV/MaNGA survey. We use mock galaxy spectra with extended star formation histories to validate our method for LTGs and use corrections to convert the derived ages into luminosity- and mass-weighted quantities. We find flat age and negative metallicity gradients for ETGs and negative age and negative metal…
