scholarly journals Determining star-formation rates in Active Galactic Nuclei hosts via stellar population synthesis

2020 ◽  
Author(s):  
Rogério Riffel ◽  
Nicolas D Mallmann ◽  
Gabriele S Ilha ◽  
Thaisa Storchi-Bergmann ◽  
Rogemar A Riffel ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
Stellar Population ◽  
Control Sample ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Host Galaxy ◽  
Population Synthesis ◽  
Stellar Population Synthesis

Abstract The effect of active galactic nuclei (AGN) feedback on the host galaxy, and its role in quenching or enhancing star-formation, is still uncertain due to the fact that usual star-formation rate (SFR) indicators – emission-line luminosities based on the assumption of photoionisation by young stars – cannot be used for active galaxies as the ionising source is the AGN. We thus investigate the use of SFR derived from the stellar population and its relation with that derived from the gas for a sample of 170 AGN hosts and a matched control sample of 291 galaxies. We compare the values of SFR densities obtained via the Hα emission line ($\rm \Sigma SFR_{Gas}$) for regions ionised by hot stars according to diagnostic diagrams with those obtained from stellar population synthesis ($\rm \Sigma SFR_\star$) over the last 1 to 100 Myr. We find that the $\rm \Sigma SFR_\star$over the last 20 Myrs closely reproduces the $\rm \Sigma SFR_{Gas}$, although a better match is obtained via the transformation: $\mbox{log($ \rm \Sigma SFR_\star $)} = (0.872\pm 0.004)\mbox{log($\rm \Sigma SFR_{Gas}$)} -(0.075\pm 0.006)$ (or $\mbox{log($\rm \Sigma SFR_{Gas}$)} = (1.147\pm 0.005)\mbox{log($ \rm \Sigma SFR_\star $)} +(0.086\pm 0.080)$), which is valid for both AGN hosts and non-active galaxies. We also compare the reddening obtained via the gas Hα/Hβ ratio with that derived via the full spectral fitting in the stellar population synthesis. We find that the ratio between the gas and stellar extinction is in the range 2.64 ≤AVg/AV⋆ ≤ 2.85, in approximate agreement with previous results from the literature, obtained for smaller samples. We interpret the difference as being due to the fact that the reddening of the stars is dominated by that affecting the less obscured underlying older population, while the reddening of the gas is larger as it is associated to a younger stellar population buried deeper in the dust.

scholarly journals Quantifying correlations between galaxy emission lines and stellar continua using a PCA-based technique

2014 ◽  
Vol 10 (S306) ◽  
pp. 301-303
Author(s):  
Róbert Beck ◽  
László Dobos ◽  
István Csabai
Keyword(s):  
Emission Line ◽  
Stellar Population ◽  
Active Galaxies ◽  
Emission Lines ◽  
Theoretical Modelling ◽  
Support Vector ◽  
Population Synthesis ◽  
Star Forming ◽  
Stellar Population Synthesis ◽  
Empirical Curve

AbstractWe analyse the correlations between continuum properties and emission line equivalent widths of star-forming and narrow-line active galaxies from SDSS. We show that emission line strengths can be predicted reasonably well from PCA coefficients of the stellar continuum using local multiple linear regression. Since upcoming sky surveys will make broadband observations only, theoretical modelling of spectra will be essential to estimate physical properties of galaxies. Combined with stellar population synthesis models, our technique will help generate more accurate model spectra and mock catalogues of galaxies to be used to fit data from new surveys. We also show that, by combining PCA coefficients from the pure continuum and the emission lines, a plausible distinction can be made between weak AGNs and quiescent star-forming galaxies. Our method uses a support vector machine, and allows a more refined separation of active and star-forming galaxies than the empirical curve of Kauffmann et al. (2003).

scholarly journals 1.8. Evolutionary population synthesis of AGN host galaxy spectra

1998 ◽  
Vol 184 ◽  
pp. 31-32
Author(s):  
W. Kollatschny ◽  
A. Goerdt
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Active Galaxies ◽  
Evolutionary Synthesis ◽  
Host Galaxy ◽  
Synthesis Methods ◽  
Population Synthesis ◽  
Host Galaxies

We compute the stellar population of nearby Seyfert host galaxies and non-active galaxies using population and evolutionary synthesis methods. We find indication of enhanced star formation rates in the host-galaxies of AGN - especially in the circumnuclear regions of Seyfert 2 galaxies.

scholarly journals Quasar Evolution and the Growth of Black Holes in the Nuclei of Active Galaxies

1989 ◽  
Vol 134 ◽  
pp. 233-239
Author(s):  
R. D. Blandford
Keyword(s):  
Black Holes ◽  
Active Galactic Nuclei ◽  
Radiation Pressure ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Rapid Decrease ◽  
Active Galaxies ◽  
Host Galaxy ◽  
Nearby Galaxies ◽  
The Mean

The observed evolutionary behavior of active galactic nuclei is compatible with a model in which black holes form in the nuclei of new-born galaxies and then grow at a rate limited by both radiation pressure and the supply of gas. Individual sources become more luminous with time as long as they are being fueled. However, the rapid decrease in the mean rate of supply of gas causes a strong decline in the space density of active objects. Nearby galaxies should harbor modest size (∼ 106 – 108 M⊙) black holes. It is suggested that the gas that fuels high redshift quasars is mostly derived from the host galaxy.

scholarly journals Tracers of Star Formation in the Near Infrared

2009 ◽  
Vol 5 (S262) ◽  
pp. 383-384
Author(s):  
L. Martins ◽  
A. Ardila ◽  
R. Gruenwald ◽  
R. de Souza
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Near Infrared ◽  
Agb Stars ◽  
Population Synthesis ◽  
Near Ir ◽  
Stellar Population Synthesis ◽  
First Time ◽  
Absorption Features ◽  
Empirical Database

AbstractStarburst features in the optical are nowadays well known, but the use of this knowledge is not always possible (e.g. objects heavily obscured). In this case the near-IR is of unprecedented value. Recent models show that TP-AGB stars should dominate the NIR spectra of populations 0.3 to 2 Gyr old. While the optical spectra is insensitive to the presence of these stars, the near-IR changes dramatically. Not only does the absolute flux in the near-IR is affected, but also peculiar absorption features appear. These features can be used as indicators of 1 Gyr stellar population. In this work we used the IRTF Spex to create the first empirical database of NIR spectra of carefully selected starbursts, to test for the first time and in a consistent way the new stellar population models that account for the TP-AGB. The methodology used is to do stellar population synthesis in the optical and in the NIR, and compare the predictions of both spectral regions. We also compare the strength of important features of the TP-AGB stars, like the CN (1.1 microns) and CO (2.3 microns) bands with optical diagnostics.

The relation between the environment and nuclear activity in nearby QSOs: Defining a control sample

2020 ◽  
Vol 15 (S359) ◽  
pp. 339-341
Author(s):  
Bruna L. C. Araujo ◽  
Thaisa Storchi-Bergmann ◽  
Sandro B. Rembold
Keyword(s):  
Active Galactic Nuclei ◽  
Control Sample ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Active Galaxies ◽  
Host Galaxies ◽  
Stellar Objects ◽  
Nuclear Activity ◽  
Quasi Stellar Objects

AbstractIn this study, we aim to investigate the relation between nuclear activity and the environment for luminous (L[O III] >7.63 × 1041 erg s–1) Active Galactic Nuclei (AGN) - that, at these luminosities are classified as quasi-stellar objects (QSOs) - using a sample of 436 type 2 QSOs. Recent studies suggest that there is an excess of interacting hosts in luminous AGN, indicating that interactions trigger the nuclear activity. In order to examine this, it is necessary to select a control sample of non-active galaxies, matched to the active ones by the properties of the host galaxies, such as distance and stellar mass. We present here the results of the search for such a control sample.

scholarly journals Properties of X-ray detected far-IR AGN in the green valley

2019 ◽  
Vol 15 (S356) ◽  
pp. 147-151
Author(s):  
Antoine Mahoro ◽  
Mirjana Pović ◽  
Petri Väisänen ◽  
Pheneas Nkundabakura ◽  
Beatrice Nyiransengiyumva ◽  
...  
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Far Infrared ◽  
Mass Range ◽  
Infrared Emission ◽  
Active Galaxies ◽  
X Ray ◽  
Normal Galaxies ◽  
Using Data

AbstractIn this study, we analysed active galactic nuclei in the “green valley” by comparing active and non-active galaxies using data from the COSMOS field. We found that most of our X-ray detected active galactic nuclei with far-infrared emission have star formation rates higher than the ones of normal galaxies of the same stellar mass range.

Nuclear ionised outflows in a sample of 30 local galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 249-254
Author(s):  
D. Ruschel-Dutra ◽  
T. Storchi-Bergmann ◽  
A. Schnorr-Müller
Keyword(s):  
Black Hole ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Massive Black Hole ◽  
Spatially Resolved ◽  
Outflow Rate ◽  
Mass Outflow ◽  
Coherent Picture

AbstractUnderstanding active galactic nuclei (AGN) feedback is essential for building a coherent picture of the evolution of the super massive black hole and its host galaxy. To that end we have analysed the inner kiloparsec of a sample of 30 local AGN with spatially resolved optical spectroscopy. In this talk I will review the analysis of the ionised gas for the galaxies in our sample, including kinematical maps, emission line ratios and fluxes. The W80 kinematical index is used to trace outflows, and also to provide an estimate for the outflowing velocity. Electron densities, derived from the [S II] ΛΛ6716, 6731Å lines, along with Hα luminosities and the sizes of the outflowing regions are employed in estimates of the outflowing gas mass. We find a median mass outflow rate of Ṁ = 0.3 M⊙ yr-1 and median outflow power of log [P/(erg s-1)] = 40.4.

scholarly journals Double-peak emission line galaxies in the SDSS catalogue

2020 ◽  
Vol 641 ◽  
pp. A171
Author(s):  
Daniel Maschmann ◽  
Anne-Laure Melchior ◽  
Gary A. Mamon ◽  
Igor V. Chilingarian ◽  
Ivan Yu. Katkov
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Control Sample ◽  
Host Galaxy ◽  
Late Type ◽  
Double Peak ◽  
Two Samples ◽  
Emission Line Galaxies ◽  
S0 Galaxies ◽  
Peak Emission

Double-peak narrow emission line galaxies have been studied extensively in the past years, in the hope of discovering late stages of mergers. It is difficult to disentangle this phenomenon from disc rotations and gas outflows with the sole spectroscopic measurement of the central 3″. We aim to properly detect such galaxies and distinguish the underlying mechanisms with a detailed analysis of the host-galaxy properties and their kinematics. Relying on the Reference Catalogue of Spectral Energy Distribution, we developed an automated selection procedure and found 5663 double-peak emission line galaxies at z <  0.34 corresponding to 0.8% of the parent database. To characterise these galaxies, we built a single-peak no-bias control sample (NBCS) with the same redshift and stellar mass distributions as the double-peak sample (DPS). These two samples are indeed very similar in terms of absolute magnitude, [OIII] luminosity, colour-colour diagrams, age and specific star formation rate, metallicity, and environment. We find an important excess of S0 galaxies in the DPS, not observed in the NBCS, which cannot be accounted for by the environment, as most of these galaxies are isolated or in poor groups. Similarly, we find a relative deficit of pure discs in the DPS late-type galaxies, which are preferentially of Sa type. In parallel, we observe a systematic central excess of star formation and extinction for double peak (DP) galaxies. Finally, there are noticeable differences in the kinematics: The gas velocity dispersion is correlated with the galaxy inclination in the NBCS, whereas this relation does not hold for the DPS. Furthermore, the DP galaxies show larger stellar velocity dispersions and they deviate from the Tully-Fisher relation for both late-type and S0 galaxies. These discrepancies can be reconciled if one considers the two peaks as two different components. Considering the morphological biases in favour of bulge-dominated galaxies and the star formation central enhancement, we suggest a scenario of multiple, sequential minor mergers driving the increase of the bulge size, leading to larger fractions of S0 galaxies and a deficit of pure disc galaxies.

scholarly journals A Catalog of 204 Offset and Dual Active Galactic Nuclei (AGNs): Increased AGN Activation in Major Mergers and Separations under 4 kpc

2021 ◽  
Vol 923 (1) ◽  
pp. 36
Author(s):  
Aaron Stemo ◽  
Julia M. Comerford ◽  
R. Scott Barrows ◽  
Daniel Stern ◽  
Roberto J. Assef ◽  
...  
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Galaxy Mergers ◽  
Mass Ratio ◽  
Merging Galaxies ◽  
Pair Separation

Abstract During galaxy mergers, gas and dust are driven toward the centers of merging galaxies, triggering enhanced star formation and supermassive black hole (SMBH) growth. Theory predicts that this heightened activity peaks at SMBH separations <20 kpc; if sufficient material accretes onto one or both of the SMBHs for them to become observable as active galactic nuclei (AGNs) during this phase, they are known as offset and dual AGNs, respectively. To better study these systems, we have built the ACS-AGN Merger Catalog, a large catalog (N = 204) of uniformly selected offset and dual AGN observed by the Hubble Space Telescope at 0.2 < z < 2.5 with separations <20 kpc. Using this catalog, we answer many questions regarding SMBH−galaxy coevolution during mergers. First, we confirm predictions that the AGN fraction peaks at SMBH pair separations <10 kpc; specifically, we find that the fraction increases significantly at pair separations of <4 kpc. Second, we find that AGNs in mergers are preferentially found in major mergers and that the fraction of AGNs found in mergers follows a logarithmic relation, decreasing as merger mass ratio increases. Third, we do not find that mergers (nor the major or minor merger subpopulations) trigger the most luminous AGNs. Finally, we find that nuclear column density, AGN luminosity, and host galaxy star formation rate have no dependence on SMBH pair separation or merger mass ratio in these systems, nor do the distributions of these values differ significantly from that of the overall AGN population.

scholarly journals Host galaxy properties and environment of obscured and unobscured X-ray selected active galactic nuclei in the COSMOS survey

2020 ◽  
Vol 494 (1) ◽  
pp. 1189-1202 ◽  
Author(s):  
C Bornancini ◽  
D García Lambas
Keyword(s):  
Active Galactic Nuclei ◽  
Formation Rate ◽  
Control Sample ◽  
Galactic Nuclei ◽  
Local Environment ◽  
Spectroscopic Properties ◽  
Stellar Mass ◽  
Host Galaxy ◽  
X Ray ◽  
Star Forming

ABSTRACT We analyse different photometric and spectroscopic properties of active galactic nuclei (AGNs) and quasars (QSOs) selected by their mid-IR power-law and X-ray emission from the COSMOS survey. We use a set of star-forming galaxies as a control sample to compare with the results. We have considered samples of obscured (HR &gt; −0.2) and unobscured (HR &lt; −0.2) sources including AGNs with LX &lt; 1044 erg s−1, as well as QSOs (LX &gt; 1044 erg s−1) with 1.4 ≤ z ≤ 2.5. We also study the typical environment of these samples, by assessing neighbouring galaxy number density and neighbour properties such as colour, stellar mass, and star formation rate. We find that the UV/optical and mid-infrared colour distribution of the different AGN types differ significantly. Also, we obtain most of AGNs and QSOs to be more compact when compared to the sample of SF galaxies. In general we find that the stellar mass distribution of the different AGN sample are similar, obtaining only a difference of $\Delta \overline{\mathrm{log}M}=0.3$ dex (M⊙) between unobscured and obscured QSOs. Obscured and unobscured AGNs and QSOs reside in different local environment at small (rp &lt; 100 kpc) scales. Our results support previous findings where AGN type correlates with environment. These differences and those found in AGN host properties cast out the simplest unified model in which obscuration is purely an orientation effect.

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