J/ApJ/805/181 Classification of 1.5≤z≤3 HUDF galaxies (Cibinel+, 2015)
A physical approach to the identification of high-z mergers: morphological
classification in the stellar mass domain.
Cibinel A., Le Floc'h E., Perret V., Bournaud F., Daddi E., Pannella M.,
Elbaz D., Amram P., Duc P.-A.
<Astrophys. J., 805, 181 (2015)>
=2015ApJ...805..181C 2015ApJ...805..181C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Redshifts ; Morphology
Keywords: galaxies: high-redshift; galaxies: interactions; galaxies: irregular;
galaxies: structure
Abstract:
At z≳1, the distinction between merging and "normal" star-forming
galaxies based on single band morphology is often hampered by the
presence of large clumps which result in a disturbed, merger-like
appearance even in rotationally supported disks. In this paper we
discuss how a classification based on canonical, non-parametric
structural indices measured on resolved stellar mass maps, rather than
on single-band images, reduces the misclassification of clumpy but not
merging galaxies. We calibrate the mass-based selection of mergers
using the MIRAGE hydrodynamical numerical simulations of isolated and
merging galaxies which span a stellar mass range of
109.8-1010.6M☉ and merger ratios between 1:1-1:6.3. These
simulations are processed to reproduce the typical depth and spatial
resolution of observed Hubble Ultra Deep Field (HUDF) data. We test
our approach on a sample of real z~=2 galaxies with kinematic
classification into disks or mergers and on ∼100 galaxies in the HUDF
field with photometric/spectroscopic redshift between 1.5≤z≤3 and
M>109.4M☉. We find that a combination of the asymmetry AMASS
and M20,MASS indices measured on the stellar mass maps can
efficiently identify real (major) mergers with ≲20% contamination
from clumpy disks in the merger sample. This mass-based classification
cannot be reproduced in star-forming galaxies by H-band measurements
alone, which instead result in a contamination from clumpy galaxies
which can be as high as 50%. Moreover, we find that the mass-based
classification always results in a lower contamination from clumpy
galaxies than an H-band classification, regardless of the depth of the
imaging used (e.g., CANDELS versus HUDF).
Description:
For galaxies in the original HUDF ACS field (3'x3') we generated two
versions of the mass maps using either (1) the deep HST/ACS F435W,
F606W, F775W and F850LP images from HUDF (Beckwith et al. 2006,
J/AJ/132/1729) combined with the HST/WFC3 F105W, F125W and F160W
images from the CANDELS-Deep survey (Grogin et al.
2011ApJS..197...35G 2011ApJS..197...35G; Koekemoer et al. 2011ApJS..197...36K 2011ApJS..197...36K), or (2) the
F435W, F606W, F775W and F850LP observations from the GOODS survey
(Giavalisco et al. 2004, II/261) plus the CANDELS-Deep NIR photometry.
For the sub-set of galaxies in the central 2'x2' region of HUDF
(corresponding to the WFC3 field of view), we also generated a third
mass map making use of the extremely deep observations available at
all wavelengths: the optical HUDF images and the HST/WFC3 F105W,
F125W, F140W and F160W coverage from the HUDF09 and HUDF12 surveys
(Bouwens et al. 2011ApJ...737...90B 2011ApJ...737...90B; Ellis et al. 2013ApJ...763L...7E 2013ApJ...763L...7E).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 74 132 Classification of HUDF galaxies
--------------------------------------------------------------------------------
See also:
II/261 : GOODS initial results (Giavalisco+, 2004)
J/AJ/148/137 : Merging galaxies in COSMOS to z∼1 (Lackner+, 2014)
J/ApJ/780/34 : H160-selected cat. of galaxies in the HUDF (Lundgren+, 2014)
J/ApJ/776/71 : ZENS: gal. in groups along the cosmic web. I. (Carollo+, 2013)
J/ApJS/207/24 : GOODS-S CANDELS multiwavelength catalog (Guo+, 2013)
J/ApJ/768/74 : PHIBSS: CO obs. of star-forming galaxies (Tacconi+, 2013)
J/A+A/539/A91 : MASSIV I. Sample properties (Contini+, 2012)
J/ApJS/203/24 : Structural param. of galaxies in CANDELS (van der Wel+, 2012)
J/ApJ/743/146 : HST/WFC3 observations in HUDF and GOODS-S (Cameron+, 2011)
J/ApJ/735/86 : NEWFIRM MBS: photometric catalogs (Whitaker+, 2011)
J/ApJ/735/L22 : HUDF galaxy properties at z∼2 (Szomoru+, 2011)
J/ApJ/706/1364 : SINS survey of high-redshift gal. (Forster Schreiber+, 2009)
J/AJ/132/1729 : Hubble Ultra Deep Field BVI-dropout sources (Beckwith+, 2006)
J/AJ/132/926 : Galaxies in the Hubble Ultra Deep Field (Coe+, 2006)
J/AJ/128/163 : Galaxy morphological classification (Lotz+, 2004)
J/ApJS/147/1 : Classification of nearby galaxies (Conselice+, 2003)
J/ApJ/588/218 : i*g* photometry of SDSS EDR galaxies (Abraham+, 2003)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID [8740/17172] CANDELS number of the galaxy (1)
6 A1 --- f_ID [*] *: strong contamination from neighboring
objects
8- 15 F8.5 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 25 F9.5 deg DEdeg Declination in decimal degrees (J2000)
27- 30 F4.2 --- z [1.4/3] Photometric redshift
32 A1 --- f_z [s] Indicates z is a spectroscopic redshift
34- 38 F5.2 --- M20MASS [-2.3/-0.6] The M20 mass index from the mass
map (2)
40- 43 F4.2 --- e_M20MASS [0.01/0.3] Uncertainty in M20MASS
45- 49 F5.3 --- AMASS [0.01/0.6] Asymmetry index from the mass map (2)
51- 55 F5.3 --- e_AMASS [0.005/0.2] Uncertainty in AMASS
57- 68 A12 --- Class Classification (3)
70- 74 A5 --- Phot Photometric data used for mass map generation (4)
--------------------------------------------------------------------------------
Note (1): From Guo et al. (2013, J/ApJS/207/24;
in Simbad) catalog.
Note (2): The asymmetry A, is the normalized residual flux as obtained from the
difference between the original image and its 180°-rotated version
(Conselice 2003, J/ApJS/147/1; Zamojski et al. 2007ApJS..172..468Z 2007ApJS..172..468Z).
M20 is the normalized second-order moment of the 20% brightest
pixels (Lotz et al. J/AJ/128/163), describing the spatial distribution
of bright clumps. See sections 5.1 and 6.2.
Note (3): According to the structural measurements performed on the mass maps:
galaxies flagged as "Merger (1)" are merger candidates selected with
the criterion in Equation 1, whereas galaxies flagged as "Merger (2)"
also satisfy the depth-dependent selection in Equation 2. Galaxies
flagged as "Unres./Faint" fall below our limits of r_KRON>5xPSF
and/or H<24.5 for a reliable mass estimate.
Note (4): Code as follows:
H+C = HUDF+CANDELS;
H+H12 = HUDF+HUDF12.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Sep-2015