Galactic Clustering Around AGN in HSC Survey

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Explore the clustering of galaxies around AGN in the Hyper Suprime-Cam Subaru Strategic Program survey, shedding light on the evolution of galaxies and supermassive black holes. This study delves into the mechanisms of gas accretion to SMBHs and the interplay between host galaxies and SMBHs. By extending previous works to higher redshifts, valuable insights are gained into the environment of AGNs, galaxy clustering, and more.

  • Galactic Clustering
  • AGN
  • HSC Survey
  • SMBH Evolution
  • Galaxy Relationships
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  1. Clustering of galaxies around AGN Clustering of galaxies around AGN in the in the HSC HSC Wide survey Wide survey published in PASJ HSC special issue arXiv:1704.05971 Yuji Shirasaki (NAOJ), Masayuki Akiyama (Tohoku U.), Tohru Nagao (Ehime U.), Yoshiki Toba (ASIAA), Wanqiu He (Tohoku U.), Masatoshi Ohishi (NAOJ), Yoshihiko Mizumoto (NAOJ), Satoshi Miyazaki (NAOJ), Atsushi J. Nishizawa (Nagoya U.), Tomonori Usuda (NAOJ) 1

  2. Introduction SMBHs (MBH= 106~1010M ) reside at the center of most galaxies. Evidence of co-evolution between host galaxy and SMBH has been obtained. Evolution of galaxies and SMBHs need to be discussed under a unified picture. Important open questions - mechanism of the gas accretion to SMBH - How is the evolution of a host galaxy and SMBH regulated : AGN feed back ? 2

  3. Model of the gas accretion to SMBH 1. secular process in the galaxy - bar and disk instability 2. external process - tidal interaction with nearby galaxy - major/minor galaxy merger 3. quiescent accretion of - hot halo gas from intra-cluster medium (ICM) - recycled gas from evolving stars Alexander+12 #1 could operate in lower-luminosity AGNs (Seyfert) #2 can explain the activity of higher-luminosity AGNs (QSO) #3 is a plausible mechanism to evolve SMBH above 109M 3

  4. Clustering of galaxies around AGN Measure of the local density where gas accretion to SMBH occurring - dependence of local density (frequency of merger) on MBH (mass accretion history) Previous studies (z < 1.0) - Komiya+13 and Shirasaki+16 detected a clustering dependence on MBH. - Krumpe+15 also detected a weak clustering dependence with MBHin 2.7 Shirasaki+16 Krumpe+15 4

  5. Objective of this work extends the works of Komiya+13 and Shirasaki+16 (z < 1.0) up to redshift ~3 The epoch covering the peak of star formation and mass accretion rate for SMBH Using the data of Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Measure the environment of AGNs - clustering of galaxies - red / blue galaxy fraction - luminosity function - their dependence on MBH First opportunity to derive those properties from a statistically significant number of AGN samples (~ thousands). 5

  6. Data set AGN Shen+11 QSO properties from SDSS-DR7 Paris+17 SDSS DR12 Quasar Catalog (DR12Q) RA, Dec, z, MBH(single epoch virial mass, MBH~ 0.4dex) Galaxy HSC-SSP Survey (Deep) (S15b) 240 deg2 i ~ 25.5 mag detection in griz-band # of AGN 5,345 (griz-band) Grouped by z & MBH z0 ~ z4 M8 : lower mass group M9 : higher mass group 6

  7. Analysis method (1/2) AGN-Galaxy cross-correlation function (1) (r) : galaxy density at r from AGN 0 : average density at the AGN redshift r0 : cross-correlation length : fixed to 1.8 (2) (3) 1. Measure the projected number densities of HSC sources at distance rpfrom each AGN : n(rp) 2. Calculate the average <n(rp)> for each AGN group. r0 3. Fit the Eq. (3) to <n(rp)>, then obtain r0. 7

  8. Analysis method (2/2) Color and Magnitude distribution of galaxies around AGN Subtract the color/magnitude distribution at lower density region (7 - 9 Mpc) from that at higher density region (0.2 2 Mpc) : On-Off subtraction distribution for galaxies associated with the corresponding AGN SED fit at a fixed redshift (=AGN s z) for all HSC sources at rp< 10 Mpc EAZY (Brammer+08) Definition of color (D) and absolute magnitude (M ) z = 0.6~2.0 D1= M 270 M 380, M 310 z = 1.5~3.0 D2= M 165 M 270, M 220 D M 8

  9. Result (1/4) : r0vs z, M Dependence of r0on z and M For galaxies brighter than a given threshold value Plotted as a function of M*- <M > for each redshift group 1. Galaxies more luminous than M*are clustered more than less- luminous galaxies. 2. Clustering of luminous galaxies increases as redshift increases. 3. Clustering of galaxies less luminous than M*is constant within stat. error (~6h-1Mpc) 9

  10. Result (2/4) : LF of clustering galaxies Derived by On-Off subtraction Compared with LFs scaled by the factor corresponding to r0. Over-density of luminous galaxies (M<M*) Fit the Schechter function M* Deviation of M*from the average is larger for higher redshift. 10

  11. Result (3/4) : r0vs MBH Crucial to remove the effect of z and M dependence AGN samples matched in redshift (dz = 0.02) are used Galaxies of M < M90% (> 90% completeness) are used No significant dependence on MBH for whole galaxy sample Red galaxies tendency of increase in clustering with MBH 11

  12. Result (4/4) : fbluevs MBH on-off subtraction Fraction of blue galaxy in our sample > 70% (each redshift group) MBHdependence Higher red fraction for larger MBH group 12

  13. Discussion (1/3) Too large clustering was measured for luminous galaxies r0= 10 ~ 40 h-1Mpc for M < M* Consistent with previous clustering studies ? r0~ 10 h-1Mpc at most for the brightest galaxies (Zehavi+11, Ishikawa+15). To be consistent, the measured strong clustering should be localized around the AGNs Clustering of less luminous galaxies r0~ 6 h-1Mpc for M > M* Mh= 1012.5~13.0 M (DM halo mass) Consistent with previous clustering studies. 13

  14. Discussion (2/3) Implication of the association between AGNs and luminous galaxies Direct interaction between them unrealistic to affect to galaxies separated by a few Mpc ? Environmental effect in a cluster or group Interaction with ICM or cluster potential Interaction between clusters/groups Concurrent interactions between galaxies at multiple sites 14

  15. Discussion (3/3) Different MBHdependence for blue/red galaxies Star-formation shift the LF to brighter side: mild increase in the # of typical (M>M*) blue galaxies, while significant increase in the # of luminous (M<M*) ones. Quenching conversion of blue to red: decrease in blue and increase in red Total number of galaxies will change only mildly, while the increase in the fraction of red can be significant in the case that the red fraction is small before the transition. 5 / 11 3 / 10 15

  16. Summary Environment of AGN (MBH>108M , z= 0.6~3.0) was examined. clustering, color, LF, and their MBHdependence, Over-density of luminous galaxies around the AGNs. Environmental effect in ICM Cluster/Group interaction Indication of MBH dependence Red galaxy fraction is larger for the large MBH Simple toy model of star-formation followed by quenching may fit to the observation qualitatively Environment has an important role in the evolution of SMBH to MBH > 108 M 16

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