J/ApJ/658/778 Spitzer mid-IR spectroscopy of z∼2 ULIRGs (Yan+, 2007)
Spitzer mid-infrared spectroscopy of infrared luminous galaxies at z ∼ 2.
I. The spectra.
Yan L., Sajina A., Fadda D., Choi P., Armus L., Helou G., Teplitz H.,
Frayer D., Surace J.
<Astrophys. J. 658, 778-793 (2007)>
=2007ApJ...658..778Y 2007ApJ...658..778Y
ADC_Keywords: Galaxies, IR ; Redshifts ; Spectroscopy ; Active gal. nuclei ;
Photometry, infrared
Keywords: galaxies: evolution - galaxies: high-redshift - galaxies: starburst
infrared: galaxies
Abstract:
We present the mid-infrared spectra obtained with the Spitzer IRS for
52 sources, selected as infrared luminous, z≳1 candidates in the
Extragalactic First Look Survey (XFLS). The sample selection criteria
are F24um≳0.9mJy, vFv(24um)/vFv(8um)≳3.16, and
vFv(24um)/vFv(0.7um)≳10. Of the 52 spectra, 47 (90%) produced
measurable redshifts based solely on the mid-IR spectral features,
with 35/47 (74%) at 1.5≲z≲3.2. Keck spectroscopy of a subsample
(17/47) agrees with the mid-IR redshift measurements. The observed
spectra fall into three categories: (1) 33% (17/52) have strong PAH
emission and are probably powered by star formation with total IR
luminosity roughly a factor of 5 higher than the local starburst
ULIRGs; (2) 33% (17/52) have only deep silicate absorption at 9.8um,
indicating deeply embedded dusty systems -these data alone cannot
determine the energetic nature of the heating sources in these
systems; and (3) the remaining 34% are mid-IR continuum-dominated
systems with weak PAH emission and/or silicate absorption. This
subsample is probably AGNs.
Description:
All observations were taken using IRS Staring mode, with nearby bright
stars as peak-up targets to accurately center the slit on the science
targets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 52 IRS Low-Resolution spectroscopy observation log
table2.dat 63 52 The measured redshifts and types for our sample
table3.dat 99 17 The Keck spectroscopy of the IRS sample
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See also:
J/AJ/125/2411 : SIRTF First-Look Survey (Condon+, 2003)
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)
J/A+A/467/565 : z=1-3 ULIRGs from the Spitzer SWIRE survey (Berta+, 2007)
http://ssc.spitzer.caltech.edu/fls/extragal/ : Extragalactic First Look Survey
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [MIPS]
6- 10 I5 --- MIPS MIPS identification number
12- 16 A5 --- --- [SST24]
18- 36 A19 --- SST24 SST24 identification (JHHMMSS.ss+DDMMSS.s)
38- 45 F8.3 mJy F24um Flux at 24um
47- 53 F7.3 uJy F8um Flux at 8um
55- 59 F5.3 uJy FR Flux at R-band (or 2σ limit)
61- 67 A7 s SL1 IRS Short-Low first order resolution (7.4-14.5um)
69- 75 A7 s LL2 IRS Long-Low second order resolution (14-21.3um)
77- 83 A7 s LL1 IRS Long-Low first order resolution (19.5-38um)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [MIPS]
6- 10 I5 --- MIPS MIPS identification number
12- 15 F4.2 --- z ?=- Redshift (no redshift for Type=4)
17- 20 F4.2 --- e_z ? Redshift uncertainty
22- 26 F5.2 [solLum] logL5.8 ?=- Estimated rest-frame luminosity at 5.8um
28- 31 F4.2 [solLum] e_logL5.8 ? Uncertainty in logL5.8um
33 A1 --- q_z [ab-] Redshift quality flag (1)
35- 37 F3.1 --- Type Spectral group classification (2)
39- 63 A25 --- Feat Spectral features used for redshift
measurements
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Note (1): Redshift quality flag as follows:
a = Secure identification
b = Spectral features whose identifications are ambiguous
Note (2): Type as follows:
1 = Systems with strong PAH emission
2 = Sources without any evidence for PAH emission, but with a strong 9.8um
silicate absorption feature
1.5 = Intermediate sources between these two types, i.e., with strong Si
absorption, as well as prominent 8um bumps, which are possibly due to
PAH emission (occasionally supported by 6.2um features)
3 = Sources with strong continuum plus weak PAH emission and/or silicate
absorption features
4 = Sources with pure power-law continua without identifiable features.
See section 4.2 for further details.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- Inst [NLD] Instrument used for data (1)
3- 6 A4 --- --- [MIPS]
8- 12 I5 --- MIPS MIPS identification number
14- 19 F6.4 --- zKeck Redshift from Keck
21- 24 F4.2 --- zIRS Redshift from IRS
26- 50 A25 --- IRS Source type classified from the IRS
52- 99 A48 --- Keck Source type from the optical spectra
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Note (1): Instrument flag as follows:
N = NIRSPEC on the Keck Telescopes
L = LRIS on the Keck Telescopes
D = DEIMOS on the Keck Telescopes
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History:
From electronic version of the journal
References:
Sajina et al. Paper II. 2007ApJ...664..713S 2007ApJ...664..713S
Sajina et al. Paper III. 2008ApJ...683..659S 2008ApJ...683..659S
(End) Emmanuelle Perret [CDS] 25-Feb-2010