J/ApJ/683/114 IRS spectra of faint IRAS sources (Sargsyan+, 2008)
Spitzer IRS spectra of optically faint IRAS sources.
Sargsyan L., Mickaelian A., Weedman D., Houck J.
<Astrophys. J., 683, 114-122 (2008)>
=2008ApJ...683..114S 2008ApJ...683..114S
ADC_Keywords: Active gal. nuclei ; Equivalent widths ; Photometry, infrared ;
Redshifts ; Spectra, infrared
Keywords: galaxies: active - galaxies: starburst - infrared: galaxies
Abstract:
Extragalactic sources from the IRAS Faint Source Catalog (FSC) that
have the optically faintest magnitudes (E≳18) were selected by
spatial coincidence with a source in the FIRST radio survey, and 28 of
these sources have been observed with the Infrared Spectrograph on
Spitzer (IRS). While an infrared source is always detected with the
IRS at the FIRST position, only ∼50% of the infrared sources are real
FSC detections, as estimated from the number of sources for which the
fv(25um) determined with the IRS is fainter than the sensitivity
limit for the FSC. Sources have 0.12<z<1.0 and luminosities
43.3<log[νLν(5.5um)]<46.7erg/s, encompassing the range from
local ULIRGs to the most luminous sources discovered by Spitzer at
z∼2. Detectable PAH features are found in 15 of the sources (54%), and
measurable silicate absorption is found in 19 sources (68%); both PAH
emission and silicate absorption are present in 11 sources. PAH
luminosities are used to determine the starburst fraction of
bolometric luminosity, and model predictions for a dusty torus are
used to determine the AGN fraction of luminosity in all sources based
on vLv(5.5um). Approximately half of the sources have luminosity
dominated by an AGN and approximately half by a starburst.
Description:
We have obtained IRS low-resolution spectra for 24 sources, and an
additional 4 have been observed in other Spitzer programs. Details of
the Spitzer IRS observations are in Table 1. Final spectra were
boxcar-smoothed to the approximate resolution of the different IRS
modules (0.2um for short low modules, SL1 and SL2 (wavelength range
5.2-14.5um), 0.3um for long low module, LL2, and 0.4um for LL1
(wavelength range 14.0-38.0um).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 70 28 IRS observations of sources
table2.dat 103 28 Observed properties of sources
table3.dat 59 28 Luminosities of sources
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See also:
II/156 : IRAS Faint Source Catalog, |b| > 10, Version 2.0 (Moshir+ 1989)
VIII/71 : The FIRST Survey Catalog, Version 03Apr11 (Becker+ 2003)
J/ApJ/642/673 : IR-selected obscured AGN candidates (Polletta+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Sequence running number
4- 6 A3 --- --- [FSC]
8- 17 A10 --- FSC Source name from the IRAS Faint Source
Catalog (II/156) (1)
19- 36 A18 --- FIRST Coordinates for the FIRST source (2)
38- 45 I8 --- AOR Astronomical Observation Request identification
number
47- 51 I5 --- Prog Program identification number
53- 55 I3 s Tsl Total integration time for IRS short-low
modules
57- 59 I3 s Tll Total integration time for IRS long-low
modules
61- 70 A10 "YYYY/MM/DD" Date Date of IRS observation
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Note (1): Sources are in Simbad.
14589+2329 is a misprint for 14589+2340, corrected at CDS.
Note (2): Coordinates for the FIRST source that is closest to the FSC source
(HHMMSS.ss+DDMMSS.s, J2000)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Sequence running number
4- 8 I5 --- Id Source number
10- 14 F5.3 --- z Redshift determined from the IRS spectra
15 A1 --- r_z [fg] References for two redshifts (3)
17- 19 I3 mJy F25i IRAS-FSC flux at 25um (Cat. II/156)
21- 25 F5.1 mJy F25s Spitzer/IRS measured flux at 25um
27- 30 F4.1 mag Emag Photographic E magnitude from APS catalog
(Cabanela et al., 2003PASP..115..837C 2003PASP..115..837C)
32 A1 --- l_Jmag Limit flag on Jmag
33- 37 F5.2 mag Jmag 2MASS J magnitude
39- 43 F5.2 mJy F1.4G ? FIRST flux at 1.4GHz
45- 48 F4.2 --- q ? Ratio of infrared to radio flux (4)
50- 54 F5.2 mJy F5.5 Spitzer/IRS flux at 5.5um
56- 60 F5.1 mJy F15 Spitzer/IRS flux at 15um
62 A1 --- l_EW Limit flag on EW
63- 67 F5.3 um EW ? Equivalent width of PAH at 6.2um
69- 73 F5.3 um e_EW ? Uncertainty on EW (5)
75 A1 --- l_F6.2 Limit flag on F6.2um
76- 80 F5.2 zW/cm2 F6.2 ? Total Spitzer/IRS flux of PAH at 6.2um (5)
82- 85 F4.2 zW/cm2 e_F6.2 ? Uncertainty on F6.2 (5)
87 A1 --- l_F11.3 Limit flag on F11.3
88- 92 F5.2 zW/cm2 F11.3 ? Total Spitzer/IRS flux of PAH at 11.3um (5)
94- 97 F4.2 zW/cm2 e_F11.3 ? Uncertainty on F11.3um (5)
99-103 F5.2 --- tau τsi measure of the depth of the 9.7um
absorption feature (6)
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Note (3): References as follows:
f = Redshift for this object, a red quasar, is the optical redshift from
Urrutia et al., 2005ApJ...627...75U 2005ApJ...627...75U
g = Redshift for this object, a blazar, is from Perry et al.,
1978PASP...90..337P 1978PASP...90..337P
Note (4): In the observed frame, q=log[fν(25um)/fν(1.4GHz)],
using fν(1.4GHz) of "peak flux" from FIRST, corresponding to an
unresolved source.
Note (5): Total flux of feature, fit with a single Gaussian. Uncertainties
in fluxes and equivalent widths are statistical uncertainties from
fitting the feature and do not include systematic uncertainties of
≲10%, which may arise from the fitting procedure chosen, as discussed
in text.
Note (6): Quantity defined as τsi=ln[fν(abs)/fν(cont)], for
fv(abs) measured at the maximum depth of absorption and fv(cont)
is the unabsorbed continuum as extrapolated in Spoon et al.,
2007ApJ...654L..49S 2007ApJ...654L..49S
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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- 2 I2 --- Seq Sequence running number
4- 8 I5 --- Id Source number
10- 13 I4 Mpc Dist Luminosity distance (7)
15- 19 F5.2 [10-7W] L5.5 Rest-frame parameter log(νLν) at 5.5um
21- 25 F5.2 [10-7W] L15 Rest-frame log(νLν) at 15um
27 A1 --- l_L6.2 Limit flag on L6.2
28- 32 F5.2 [10-7W] L6.2 ? Total luminosity of the 6.2um PAH feature,
after subtracting the underlying continuum
34 A1 --- l_Ls Limit flag on Ls
35- 39 F5.2 [10-7W] Ls ? logL(6.2+11.3)
41 A1 --- l_LSB Limit flag on LSB
42- 46 F5.2 [10-7W] LSB ? Total luminosity of starburst (8)
48 A1 --- l_LAGN Limit flag on LAGN
49- 53 F5.2 [10-7W] LAGN ? Luminosity from the dusty torus of the AGN (9)
55 A1 --- l_f(SB) Limit flag on f(SB)
56- 59 F4.2 --- f(SB) ? Fraction of luminosity from starburst (10)
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Note (7): Luminosity distance determined by E.L. Wright
(see http://www.astro.ucla.edu/~wright/DlttCalc.html) for
H0=71km/s/Mpc, Ωm=0.27, and ΩΛ=0.73.
Note (8): Total luminosity of starburst, assuming that
log[LIR(SB)]=log[L(6.2)]+2.7±0.1, from Brandl et al.
(2006ApJ...653.1129B 2006ApJ...653.1129B) and Pope et al. (2008ApJ...675.1171P 2008ApJ...675.1171P).
Note (9): Total luminosity from the dusty torus of the AGN, assuming
log[LIR(AGN)]=log[νLν(5.5um)]+0.33±0.06, from Polletta et
al. (2008ApJ...675..960P 2008ApJ...675..960P) and assuming that all continuum luminosity
vLv(5.5um) arises from an AGN.
Note (10): Fraction L(SB)/[L(SB)+L(AGN)]. If a PAH feature is detected,
this fraction is shown as a lower limit because some of the continuum
at 5.5um, which is attributed to an AGN, actually arises from the
starburst. If no PAH feature is detected, this fraction is shown as an
upper limit because there is no direct evidence that a starburst is
present. Source 9 is a blazar, so the parameters for determining
LIR(AGN) and LIR(SB) are not applicable.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 26-Nov-2010