J/ApJ/925/70 Morphological asymmetry of massive low-z galaxies (Zhao+, 2022)
The relation between morphological asymmetry and nuclear activity in
low-redshift galaxies.
Zhao Y., Li Y.A., Shangguan J., Zhuang M.-Y., Ho L.C.
<Astrophys. J., 925, 70 (2022)>
=2022ApJ...925...70Z 2022ApJ...925...70Z
ADC_Keywords: Galaxies, interacting; Active gal. nuclei; Morphology;
Galaxies, radius
Keywords: Galaxy evolution ; Galaxy interactions ; Galaxy mergers ;
AGN host galaxies
Abstract:
The morphology of galaxies reflects their assembly history and ongoing
dynamical perturbations from the environment. Analyzing stacked i-band
images from the Pan-STARRS1 3π Steradian Survey, we study the
optical morphological asymmetry of the host galaxies of a large,
well-defined sample of nearby active galactic nuclei (AGNs) to
investigate the role of mergers and interactions in triggering nuclear
activity. The AGNs, comprising 245 type 1 and 4514 type 2 objects, are
compared with 4537 star-forming galaxies (SFGs) matched in redshift
(0.04<z<0.15) and stellar mass (M*>1010M☉). We develop a
comprehensive masking strategy to isolate the emission of the target
from foreground stars and other contaminating nearby sources, all the
while retaining projected companions of comparable brightness that may
be major mergers. Among three variants of nonparametric indices, both
the popular CAS asymmetry parameter (ACAS) and the outer asymmetry
parameter (Aouter) yield robust measures of morphological distortion
for SFGs and type 2 AGNs, while only Aouter is effective for type 1
AGNs. The shape asymmetry (Ashape), by comparison, is affected more
adversely by background noise. Asymmetry indices ≳0.4 effectively
trace systems that are candidate ongoing mergers. Contrary to
theoretical expectations, galaxy interactions and mergers are not the
main drivers of nuclear activity, at least not in our sample of low-
redshift, relatively low luminosity AGNs, whose host galaxies are
actually significantly less asymmetric than the control sample of
SFGs. Moreover, type 2 AGNs are morphologically indistinguishable from
their type 1 counterparts. The level of AGN activity does not
correlate with asymmetry, not even among the major merger candidates.
As a by-product, we find, consistent with previous studies, that the
average asymmetry of SFGs increases above the main sequence, although
not all major mergers exhibit enhanced star formation.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 118 9296 Sample and measurements
--------------------------------------------------------------------------------
See also:
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
J/ApJS/107/1 : Morphologies of distant galaxies II (Abraham+ 1996)
J/ApJS/147/1 : Classification of nearby galaxies (Conselice+, 2003)
J/PASP/117/227 : Properties of 101 galaxies from the NFGS (Kewley+, 2005)
J/ApJ/667/131 : Mass function of active black holes (Greene+, 2007)
J/MNRAS/393/1275 : STAGES master catalog (Gray+, 2009)
J/ApJS/206/10 : CANDELS multiwavelength catalog (Galametz+, 2013)
J/ApJ/804/34 : Luminous AGNs and early-type SDSS galaxies (Hong+, 2015)
J/ApJ/859/116 : BH masses and Eddington ratios of Type 2 QSOs (Kong+, 2018)
J/ApJS/244/34 : The CGS. VIII. R-band images of disk galaxies (Gao+, 2019)
J/ApJS/243/21 : Broad-line AGN from SDSS-DR7 (Liu+, 2019)
J/ApJS/256/40 : HST imaging survey of low-z Swift-BAT AGNs (Kim+, 2021)
J/ApJ/919/134 : SDSS shocked post-starburst gal. with HST (Sazonova+, 2021)
http://ps1images.stsci.edu/cgi-bin/ps1cutouts : PS1 image access
http://www.sdss.org/dr16/data_access/ : SDSS DR16 data access
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/9296] Running sequence number
6- 17 F12.8 deg RAdeg Right ascension (J2000)
19- 32 F14.10 deg DEdeg [-11.2/68.6] Declination (J2000)
34- 38 F5.3 --- z [0.04/0.15] Redshift
40- 44 F5.2 [Msun] logMs [10/11.6] Stellar mass of the host galaxy
46- 50 F5.2 [Msun/yr] logSFR [-2.5/2.1]? Star formation rate
52- 56 F5.2 [10-7W] logLOIII [39/47.2]? [OIII] Luminosity in erg/s (1)
58 I1 --- Merger [0/1]? Merger flag (2)
60- 63 F4.2 --- C [0.29/4.8] Optical concentration
65- 69 F5.2 --- ACAS [-0.4/1.2] CAS asymmetry
71- 74 F4.2 --- e_ACAS [0/0.5] Uncertainty in CAS asymmetry
76- 80 F5.2 --- Aouter [-0.22/2] Outer asymmetry
82- 85 F4.2 --- e_Aouter [0/0.6] Uncertainty in outer asymmetry
87- 90 F4.2 --- Ashape [0.08/2.1] Shape asymmetry
92- 97 F6.2 pix Prad [5/498] Petrosian radius
99- 105 F7.2 pix Rmax [12/4630] The semimajor axis of the
minimal ellipse (3)
107- 113 F7.2 pix Rhalf [2.7/3697] The semimajor axis of an
elliptical aperture that contains 50% of
the light
115- 118 A4 --- Type Subsample type (4)
--------------------------------------------------------------------------------
Note (1): Corrected for Galactic but not internal extinction.
Note (2): Merger flag as follows:
0 = no candidate major merger pair (9003 occurrences)
1 = at least one candidate major merger pair (293 occurrences)
Note (3): with fixed center, elongation, and orientation;
and contains all of the main segment of the shape asymmetry
segmentation map.
Note (4): Subsample type as follows:
AGN1 = AGN type 1 (245 occurrences)
AGN2 = AGN type 2 (4514 occurrences)
SFG = star-forming galaxy (4537 occurrences)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 30-Aug-2023