How the role of environment in fuelling AGN depends on the host galaxy

Transcription

1 How the role of environment in fuelling AGN depends on the host galaxy Ric Davies Max Planck Institute for Extraterrestrial Physics, Germany E. Hicks, P. Erwin, T. Storchi-Bergmann, L. Burtscher, A. Contursi, R. Genzel, J. Graciá-Carpio, A. Janssen, M. Koss, M.-Y. Lin, D. Lutz, W. Maciejewski, F. Müller-Sánchez, G. Orban de Xivry, R. Riffel, R.A. Riffel, D. Rosario, M. Schartmann, A. Schnorr-Müller, A. Sternberg, E. Sturm, L. Tacconi, S. Veilleux. Most AGN are in disk galaxies; but these show no evidence for environmental dependence. The fraction of AGN in S0 hosts decreases in dense environments (in contrast to the fraction of S0 galaxies itself). There are differences in luminosity function & obscuration between AGN in S0 vs disk hosts.

2 Motivation & Perspective Davies+ 14: Differences in AGN fuelling between S0 and disk hosts. Based on samples of Hicks+13, Dumas+ 07, Westoby+ 07. Used IFU data with spatially resolved stellar and gas kinematics Disk dominated hosts Secular inflow requires a large scale disk to supply the gas. (i) presence of gas in both active & inactive galaxies. (ii) gas & stars always co-rotating. -> environment doesn t matter for AGN fuelling. Bulge dominated hosts External accretion (minor mergers or streamers) is seen more easily, and has more impact, in galaxies without a plentiful supply of gas. (i) lack of gas in inactive galaxies vs presence of gas in AGN. (ii) gas & stars sometimes counter-rotating. -> environment matters for AGN fuelling: a source for the gas.

3 Sample: Swift/BAT AGN to z=0.04 with log L keV > AGN at z < 0.01 form a complete volume limited sample (LLAMA is the subset of the 20 AGN visible from VLT; Davies+ 15) 339 AGN at z < 0.04 ~200 in group catalogues & with host galaxy classifications: Tully 15 based on halo scaling relations. Tempel+16 based on friends-on-friends with refinement. Poster by Ming-yi Lin LLAMA

4 AGN luminosity and host galaxy mass AGN luminosity distribution L (14-195keV) ~ 10^43 to 10^44 erg/s L_AGN ~ 10 higher strongly peaked Galaxy mass distribution (using H-band luminosity as a proxy) L_H ~ 10^10 to 10^11 Lsun Masses are similar

5 Halo Mass or Group Size? Halo Mass: More closely linked to theoretical framework & so easier to apply in a cosmological context. Insensitive to inclusion of extra low mass galaxies. Not easy to derive for small groups. Group Size: More directly linked to observation. Differentiates between single massive galaxy & group of lower mass galaxies (although the respective halo masses may be similar). Dependent on lower mass limit (catalogue sensitivity). Rough conversion between halo mass and group size: small group cluster N gal 1 ~ >~100 Log M halo >~14.5

6 Group Catalogues Reproduce Known Galaxy Trends Fractions of disk & S0 galaxies depend strongly on environment Wilman & Erwin 12 Log Ngal ~ 0.5 Log Ngal ~ 2

7 No environmental dependence for AGN in disk galaxies The fraction of disk galaxies decreases with density, But the fraction of AGN in disk galaxies does not change. Fraction of galaxies that are disks Fraction of disk galaxies that host AGN The 2 lines represent the Tully 15 & Tempel+16 group catalogues Shaded area represents the 1σ range of a parent distribution that is consistent with the measured values for both Tully 15 & Tempel+ 16, given their bootstrapped uncertainties.

8 Environmental effects washed out by predominance of disks ~25000 galaxies at z<0.04 Most galaxies (66%) are disks. Most galaxies (62%) are in the field with Ngal <= 3. ~200 AGN at z<0.04 ~60 in S0 hosts ~130 in disk hosts Most AGN (64%) are in disk galaxies. Most AGN (71%) are in field galaxies with Ngal <= 3.

9 Strong environmental dependence for AGN in S0 galaxies The fraction of disk galaxies increases with density, But the fraction of AGN in S0 galaxies decreases. Fraction of galaxies that are S0 Fraction of S0 galaxies that host AGN The 2 lines represent the Tully 15 & Tempel+16 group catalogues Shaded area represents the 1σ range of a parent distribution that is consistent with the measured values for both Tully 15 & Tempel+ 16, given their bootstrapped uncertainties.

10 Similar dependencies for disks & S0 hosts in other samples Wilman & Erwin 12 AGN classification based on optical line ratios. Originally focussed on central vs satellite galaxies; these are combined here. Sample includes galaxies with Msun (cf the BAT sample, <11.0 Msun). The AGN fraction of S0 hosts peaks at halo masses equivalent to small group sizes, dropping rapidly in cluster environment. Less so for disks. Ngal ~ 3 clusters

11 Differences in Luminosity Function Differences between AGN with S0 hosts and disk hosts Luminosity functions are different Many more lower luminosity AGN in disk hosts Number of AGN 315 AGN Relative luminosity function 134 AGN with disk hosts 67 AGN with S0 hosts

12 Differences in Luminosity Function Remarkable similarity to Hopkins+ 14 luminosity functions. But can these be directly compared? Luminosity function is a 2ndary relation depends on BH mass function & Eddington ratio. The reason for the difference is the bulge fractions and hence BH masses in disk & S0 galaxies. BAT AGN in disk hosts BAT AGN in S0 hosts Hopkins+ 14

13 Differences in Obscuration Differences between AGN with S0 hosts and disk hosts unobscured obscured* other Sy Sy S0 host disk host Extra obscuration of A V = 3-6mag due to dust filaments & dust lanes crossing nucleus, e.g. Prieto+ 14: NGC 1386 *note that Sy 1.5 have A V ~ few mag (Schnorr-Mueller+ 16, also Burtscher+ 15,16) (also Koulouridis+ 06; Davies+ 14)

14 Summary Analysis based on: ~200 AGN from Swift/BAT survey at z<0.04 with logl >42.5 that are in group catalogues and have known host morphological classifications. Conclusions: Most AGN are in disk galaxies, and these show no evidence for environmental dependence [they have their own internal gas supply to fuel an AGN]. The fraction of S0 hosts with AGN decreases in large groups & clusters [to fuel an AGN they need to accrete gas from the environment; this is efficient in interactions & small groups, but not in clusters where the ICM is hot]. There are differences in luminosity function & obscuration between AGN in S0 hosts and disks. the bottom line The environmental dependence of AGN depends on whether they are in a disk or S0 host galaxy. And because these AGN get their gas in different ways, their luminosity functions and obscured fractions also differ.

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16 Group Catalogues 2 recent Group Catalogues based on similar galaxy catalogues but with very different approaches to identifying groups: Tully 15 2MRS Halo based method (using scaling relations), combine galaxies within same halo boundaries & iterate Host classifications given in paper based on RC3 Tempel+ 16 2MRS, CF2, 2M++ Friends-of-friends algorithm with membership refinement (to separate multi-component groups and trim field galaxies from outer edges of groups) Host classifications from cross-matching with PGC catalogue (uses RC3)

17 Halo Mass or Group Size? halo occupation numbers from Yang+ 05 (SDSS groups) data from Tempel+ 16 overlaid Rough conversion between halo mass and group size: small group cluster N gal 1* ~ >~100 Log M halo >~14.5 (* note galaxy masses are 10^10 to 10^11 Msun)

18 AGN in the field and clusters A rich & varied literature on the subject Sabater+ 15: the dependence of AGN activity on environment is not so clear. Many apparently contradictory results are still found in the literature. Li+ 06: AGN host galaxies and inactive control galaxies populate dark matter haloes of similar mass. Arnold+ 09: X-ray selected AGN fraction increases from clusters to groups Just+ 10: rapid recent growth of S0 population in groups and poor clusters Fanidakis+ 13: moderate luminosity AGN are typically found in DM haloes with masses of ~10 13 M sun. hot halo mode giving rise to moderate luminosity AGN that inhabit rich clusters & superclusters field clusters Martini+ 09