J/ApJ/730/125 HST/NICMOS observations of bright IR galaxies (Zamojski+, 2011)
HST/NICMOS imaging of bright high-redshift 24 µm selected galaxies: merging
properties.
Zamojski M., Yan L., Dasyra K., Sajina A., Surace J., Heckman T., Helou G.
<Astrophys. J., 730, 125 (2011)>
=2011ApJ...730..125Z 2011ApJ...730..125Z
ADC_Keywords: Galaxies, IR ; Photometry, HST ; Redshifts ; Morphology
Keywords: galaxies: evolution - galaxies: high-redshift - infrared: galaxies
Abstract:
We present new results on the physical nature of infrared-luminous
sources at 0.5<z<2.8 as revealed by HST/NICMOS imaging and Infrared
Spectrograph mid-infrared spectroscopy. Our sample consists of 134
galaxies selected at 24um with a flux of S(24um)>0.9mJy. We find many
(∼60%) of our sources to possess an important bulge and/or central
point source component, most of which reveal additional underlying
structures after subtraction of a best-fit Sersic (or Sersic+PSF)
profile. Based on visual inspection of the NIC2 images and their
residuals, we estimate that ∼80% of all our sources are mergers. We
calculate lower and upper limits on the merger fraction to be 62% and
91%, respectively. At z<1.5, we observe objects in early
(pre-coalescence) merging stages to be mostly disk and star formation
dominated, while we find mergers to be mainly bulge dominated and
active galactic nucleus (AGN)-starburst composites during coalescence
and then AGN dominated in late stages. This is analogous to what is
observed in local ULIRGs. Finally, we observe obscured
(τ9.7um>3.36) quasars to live in faint and compact hosts and
show that these are likely high-redshift analogs of local dense-core
mergers. We find late-stage mergers to possess predominantly
unobscured AGN spectra, but do not observe other morphological classes
to carry any specific combination of τ9.7um and polycyclic
aromatic hydrocarbon (PAH) equivalent width.
Description:
Our full sample consists of 134 galaxies with 24um fluxes above 0.9mJy
selected from the XFLS (Spitzer Extragalactic First Look Survey). In
this paper, we expand the analysis of Dasyra et al.
(2008ApJ...680..232D 2008ApJ...680..232D) and perform a systematic search of merger
signatures by uncovering underlying structures.
We have obtained HST/NIC2 F160W (H-band) images for 33 sources from
our first program (IRS spectra in Yan et al. (2007, Cat. J/ApJ/658/778),
Sajina et al. (2007ApJ...664..713S 2007ApJ...664..713S)) and 102 sources from our second
program (IRS spectra in Dasyra et al. (2009, Cat. J/ApJ/701/1123)).
In this paper, we utilize redshift measurements extracted from the IRS
data using the method described in Sajina et al. (2007ApJ...664..713S 2007ApJ...664..713S).
When available, we use more precise redshifts derived from optical or
near-infrared spectra instead (∼20 objects; Sajina et al.
2008ApJ...683..659S 2008ApJ...683..659S).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 61 134 Morphology of the 24um-selected galaxies
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See also:
J/ApJ/713/330 : Spitzer observations of major-merger galaxies (Xu+, 2010)
J/ApJ/701/1123 : MIR spectroscopic catalog of 150 galaxies (Dasyra+, 2009)
J/ApJS/177/148 : HST survey. II. Atlas of mergers & companions (Floyd+, 2008)
J/MNRAS/376/1251 : 610MHz observations of Spitzer XFLS (Garn+, 2007)
J/ApJ/658/778 : Spitzer mid-IR spectroscopy of z∼2 ULIRGs (Yan+, 2007)
J/AJ/131/250 : Spitzer 70 and 160um observations in xFLS (Frayer+, 2006)
J/AJ/131/2859 : Extragalactic First Look Survey: 24µm data (Fadda+, 2006)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [MIPS]
5- 9 I5 --- MIPS [34/22725] MIPS identification number
(<[YSF2007] MIPS NNNNN> or <[DYH2009] MIPS NNNNN>
in Simbad)
10 A1 --- f_MIPS [a] Flag on MIPS42 (1)
12- 15 F4.2 --- z [0.24/3.49]? Redshift
17- 21 F5.2 mag Hmag [17.27/23.71]? HST/NICMOS H-band magnitude
23 A1 --- u_r1/2 [~] Uncertainty flag on r1/2
24- 27 F4.2 kpc r1/2 [0.17/9.11]? Half-light radius
28 A1 --- f_r1/2 [b] Flag on r1/2 (1)
30- 38 A9 --- Comp Dominant component (Bulge, Disk or Ambiguous) (2)
40- 59 A20 --- Morph Morphological class
61 I1 --- Conf [1/6]? Confidence level (3)
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Note (1): Flag as follows:
a = MIPS42 is very close to a diffraction spike in our NICMOS image which
causes all of our fits to fail. Nevertheless, it is visually clear that
it is a disk-dominated, "faint and compact" object.
b = Assuming 1"=8kpc.
Note (2): The profile of some of our objects is listed as ambiguous. These are
objects whose profile is not well constrained either because they are
very faint, barely resolved, or possess a strong PSF component that
hides the underlying galaxy.
Note (3): Confidence classes as follows:
1 = Clear mergers
2 = Highly probable mergers
3 = Likely mergers
4 = Probable mergers
5 = Possible mergers
6 = Elliptical galaxies that are well fit with a smooth Sersic profile and
show no residuals.
See section 2.5.2 for further explanations.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 11-Oct-2012