Changing Ionization Conditions in SDSS Galaxies With Active Galactic Nuclei as a Function of Environment From Pairs to Clusters

Khabiboulline, Emil T.; Steinhardt, Charles L.; Silverman, John D.; Ellison, Sara L.; Mendel, J. Trevor; Patton, David R.

doi:10.1088/0004-637x/795/1/62

Cited by 30 publications

(31 citation statements)

References 76 publications

(132 reference statements)

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“…Much of the observational evidence for these effects is derived from studies of galaxies which exhibit strong morphological disturbances and/or galaxies which have a close companion. It is now well established that, on average, these galaxies have enhanced star formation rates (Barton, Geller, & Kenyon 2000;Ellison et al 2008a;Freedman Woods et al 2010;Scudder et al 2012;Patton et al 2013;Davies et al 2015 Plauchu- Frayn & Coziol 2010a,b;Ellison et al 2010;Casteels et al 2014), lower nuclear metallicities (Kewley, Geller, & Barton 2006;Ellison et al 2008a;Michel-Dansac et al 2008;Kewley et al 2010;Scudder et al 2012;Ellison et al 2013) and increased AGN activity (Alonso et al 2007;Silverman et al 2011;Liu, Shen, & Strauss 2012;Ellison et al 2013;Khabiboulline et al 2014;Satyapal et al 2014) compared with relatively isolated and/or undisturbed galaxies.…”

Section: Introductionmentioning

confidence: 99%

“…There are already a number of galaxy pair studies which report differences in galaxy properties at pair separations of 50-100 kpc Patton et al 2011;Scudder et al 2012;Casteels et al 2013;Ellison et al 2013;Khabiboulline et al 2014;Satyapal et al 2014) and some which report differences beyond 100 kpc (Park et al 2007;Li et al 2008;Robaina et al 2009;Park & Choi 2009;Koss et al 2010;Patton et al 2013). However, there are a number of challenges that arise when attempting to extend existing techniques out to such wide separations.…”

Section: Introductionmentioning

confidence: 99%

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Galaxy pairs in the Sloan Digital Sky Survey – XI. A new method for measuring the influence of the closest companion out to wide separations

Patton

Qamar

Ellison

et al. 2016

Mon. Not. R. Astron. Soc.

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We describe a statistical approach for measuring the influence that a galaxy's closest companion has on the galaxy's properties out to arbitrarily wide separations. We begin by identifying the closest companion for every galaxy in a large spectroscopic sample of Sloan Digital Sky Survey galaxies. We then characterize the local environment of each galaxy by using the number of galaxies within 2 Mpc and by determining the isolation of the galaxy pair from other neighbouring galaxies. We introduce a sophisticated algorithm for creating a statistical control sample for each galaxy, matching on stellar mass, redshift, local density and isolation. Unlike traditional studies of close galaxy pairs, this approach is effective in a wide range of environments, regardless of how far away the closest companion is (although a very distant closest companion is unlikely to have a measurable influence on the galaxy in question). We apply this methodology to measurements of galaxy asymmetry, and find that the presence of nearby companions drives a clear enhancement in galaxy asymmetries. The asymmetry excess peaks at the smallest projected separations (< 10 kpc), where the mean asymmetry is enhanced by a factor of 2.0 ± 0.2. Enhancements in mean asymmetry decline as pair separation increases, but remain statistically significant (1-2σ ) out to projected separations of at least 50 kpc.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Galaxy pairs in the Sloan Digital Sky Survey – XI. A new method for measuring the influence of the closest companion out to wide separations

Patton

Qamar

Ellison

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Indeed, there are now many studies that have shown that interactions over a wide range of mass ratios can 1 trigger AGN that are selected variously in the optical (e.g. Alonso et al 2007;Ellison et al 2011Ellison et al , 2013Kaviraj 2014;Khabiboulline et al 2014), mid-IR (Satyapal et al 2014;Shao et al 2015) and X-ray (Koss et al 2010(Koss et al , 2012Silverman et al 2011;Lackner et al 2014). For radio selected AGN, there is evidence to support a connection between mergers and both HERGs and the highest luminosity radio-loud AGN (e.g.…”

Section: Introductionmentioning

confidence: 99%

Galaxy pairs in the Sloan Digital Sky Survey – XII. The fuelling mechanism of low-excitation radio-loud AGN

Ellison

Patton

Hickox

2015

Monthly Notices of the Royal Astronomical Society: Letters

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We investigate whether the fuelling of low excitation radio galaxies (LERGs) is linked to major galaxy interactions. Our study utilizes a sample of 10,800 spectroscopic galaxy pairs and 97 post-mergers selected from the Sloan Digital Sky Survey with matches to multi-wavelength datasets. The LERG fraction amongst interacting galaxies is a factor of 3.5 higher than that of a control sample matched in local galaxy density, redshift and stellar mass. However, the LERG excess in pairs does not depend on projected separation and remains elevated out to at least 500 h −1 70 kpc, suggesting that major mergers are not their main fuelling channel. In order to identify the primary fuelling mechanism of LERGs, we compile samples of control galaxies that are matched in various host galaxy and environmental properties. The LERG excess is reduced, but not completely removed, when halo mass or D 4000 are included in the matching parameters. However, when both M halo and D 4000 are matched, there is no LERG excess and the 1.4 GHz luminosities (which trace jet mechanical power) are consistent between the pairs and control. In contrast, the excess of optical and mid-IR selected AGN in galaxy pairs is unchanged when the additional matching parameters are implemented. Our results suggest that whilst major interactions may trigger optically and mid-IR selected AGN, the gas which fuels the LERGs has two secular origins: one associated with the large scale environment, such as accretion from the surrounding medium or minor mergers, plus an internal stellar mechanism, such as winds from evolved stars.

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“…This pressure is able to strip gas from galaxies (ram pressure stripping), which may cause tails of stripped gas to form behind the galaxy as it moves in the cluster, as has been observed for galaxies in the Virgo cluster (e.g., Kenney et al 2004;Crowl et al 2005;Chung et al 2007). Ram pressure stripping leads to a decreased prevalence of radio-mode AGN activity in the centers of clusters (e.g., Ellison et al 2011;Ehlert et al 2014;Khabiboulline et al 2014), since the ram pressure has depleted the gas supply of these central galaxies. However, models and hydrodynamical simulations show that lower ram pressures can compress the gas in the galaxy, and may induce star formation (e.g., Fujita & Nagashima 1999;Kronberger et al 2008;Kapferer et al 2009;Tonnesen & Bryan 2009;Bekki 2014), which is also supported by observations (e.g., ).…”

Section: Comparison With Theoretical Predictionsmentioning

confidence: 95%

Spectroscopic characterization of the protocluster of galaxies around 7C 1756+6520 at z ~ 1.4

Casasola

Magrini

Combes

et al. 2018

A&A

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Aims. The aim of this paper is the spectroscopic study of 13 galaxies belonging to the field of the protocluster associated with the radio galaxy 7C 1756+6520 at z = 1.4156. In particular, we focus on the characterization of the nuclear activity.Methods. This analysis has been performed on rest-frame optical spectra taken with the Large Binocular Telescope, using the spectrograph LUCI, which is operative in the near-infrared domain. The adopted spectral coverage allowed us to observe emission lines such as Hα, Hβ, [O iii]λ 5007 Å, and [N ii]λ 6583 Å at the redshift of the central radio galaxy. We observed the central part of the protocluster, which is suitable to include the radio galaxy, several spectroscopically confirmed active galactic nuclei (AGN) belonging to the protocluster, and other objects that might be members of the protocluster. Results. For four previously identified protocluster members, we derived the redshift by detecting emission lines that have never detected before for these galaxies. We identified a new protocluster member and eight new possible protocluster members. The stacked spectrum of the galaxies in which we detected the [O iii]λ 5007 Å emission line revealed the second line of the [O iii] doublet at 4959 Å and the Hβ line, which confirms that they belong to the protocluster. By collecting all members identified so far in this work and other members from the literature, we defined 31 galaxies, including the central radio galaxy, around the redshift 1.4152 ± 0.056. This corresponds to peculiar velocities 5000 km s −1 with respect to the radio galaxy. The position versus velocity phase-space diagram suggests that three AGN of the protocluster and the central radio galaxy might be a virialized population that has been coexisting for a long time in the densest core region of this forming structure. This protocluster is characterized by a high fraction of AGN (∼23%). For one of them, AGN1317, we produced two so-called Baldwin, Phillips & Terlevich (BPT) diagrams. The high fraction of AGN and their distribution within the protocluster seem to be consistent with predictions of some theoretical models on AGN growth and feedback. These models are based on galaxy interactions and ram pressure as triggers of AGN activity. Conclusions. The high fraction of AGN belonging to the protocluster suggests that they were likely triggered at the same time, maybe by the ongoing formation of the protocluster. Observations of AGN in this protocluster and in other distant clusters will help clarifying whether the resulting high fraction of AGN is unusual or typical for such structures at high redshift. Our next step will be analyses of previously acquired high-resolution radio data of the central radio galaxy to derive information on the nature of the radio galaxy and connect it with its cosmic evolution.

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Changing Ionization Conditions in SDSS Galaxies With Active Galactic Nuclei as a Function of Environment From Pairs to Clusters

Cited by 30 publications

References 76 publications

Galaxy pairs in the Sloan Digital Sky Survey – XI. A new method for measuring the influence of the closest companion out to wide separations

Galaxy pairs in the Sloan Digital Sky Survey – XI. A new method for measuring the influence of the closest companion out to wide separations

Galaxy pairs in the Sloan Digital Sky Survey – XII. The fuelling mechanism of low-excitation radio-loud AGN

Spectroscopic characterization of the protocluster of galaxies around 7C 1756+6520 at z ~ 1.4

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