J/ApJ/862/96 Dusty star-forming galaxies with LABOCA 870um obs. (Lewis+, 2018)
Ultra-red galaxies signpost candidate protoclusters at high redshift.
Lewis A.J.R., Ivison R.J., Best P.N., Simpson J.M., Weiss A., Oteo I.,
Zhang Z.-Y., Arumugam V., Bremer M.N., Chapman S.C., Clements D.L.,
Dannerbauer H., Dunne L., Eales S., Maddox S., Oliver S.J., Omont A.,
Riechers D.A., Serjeant S., Valiante E., Wardlow J., van der Werf P.,
De Zotti G.
<Astrophys. J., 862, 96 (2018)>
=2018ApJ...862...96L 2018ApJ...862...96L
ADC_Keywords: Galaxies, IR ; Millimetric/submm sources ;
Photometry, infrared ; Opacities ; Redshifts
Keywords: galaxies: clusters: general ; galaxies: high-redshift ;
galaxies: starburst ; infrared: galaxies ; submillimeter: galaxies
Abstract:
We present images obtained with LABOCA of a sample of 22 galaxies
selected via their red Herschel SPIRE colors. We aim to see if these
luminous, rare, and distant galaxies are signposting dense regions in
the early universe. Our 870µm survey covers an area of ∼1deg2
down to an average rms of 3.9mJy/beam, with our five deepest maps
going 2x deeper still. We catalog 86 dusty star-forming galaxies
(DSFGs) around our "signposts," detected above a significance of
3.5σ. This implies a 100±30% overdensity of S870>8.5mJy (or
LFIR=6.7x1012-2.9x1013L☉) DSFGs, excluding our signposts,
when comparing our number counts to those in "blank fields." Thus, we
are 99.93% confident that our signposts are pinpointing overdense
regions in the universe, and 95% [50%] confident that these regions
are overdense by a factor of at least ≥1.5x[2x]. Using template
spectral energy distributions (SEDs) and SPIRE/LABOCA photometry, we
derive a median photometric redshift of z=3.2±0.2 for our signposts,
with an inter-quartile range of z=2.8-3.6, somewhat higher than
expected for 850µm selected galaxies. We constrain the DSFGs that
are likely responsible for this overdensity to within
|δz|≤0.65 of their respective signposts. These "associated"
DSFGs are radially distributed within (physical) distances of
1.6±0.5Mpc from their signposts, have median star formation rates
(SFRs) of ~(1.0±0.2)x103M☉/yr (for a Salpeter stellar initial
mass function) and median gas reservoirs of ∼1.7x1011M☉. These
candidate protoclusters have average total SFRs of at least
~(2.3±0.5)x103M☉/yr and space densities of 9x10-7Mpc-3,
consistent with the idea that their constituents may evolve to become
massive early-type galaxies in the centers of the rich galaxy clusters
we see today.
Description:
We selected 12 targets-based on their initial shallow 850um imaging
from the H-ATLAS (Herschel Astrophysical Terahertz Large Area Survey;
Eales+ 2010PASP..122..499E 2010PASP..122..499E) imaging survey. Our selection criteria are
discussed fully in Paper I (Ivison+ 2016ApJ...832...78I 2016ApJ...832...78I). To this
H-ATLAS sample, we added an additional 10 targets from five fields in
the HerMES (Herschel Multi-tiered Extragalactic Survey;
Oliver+ 2012, VIII/95) imaging survey.
See section 2.1 for further details.
Our sample of 22 ultra-red galaxies were imaged with the Atacama
Pathfinder Experiment (APEX) telescope's Large APEX BOlometer CAmera
(LABOCA) instrument over six observing runs from 2012 September to
2014 March. The passband response for this instrument is centered on
870µm (345GHz) and has a half-transmission width of 150µm (60GHz).
We catalog 108 dusty star-forming galaxies (DSFGs; 86 field galaxies
around our 22 ultra-red galaxies) from our 22 maps above
Σthresh>3.5 and list their SPIRE and LABOCA parameters in
Table 5.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 92 22 Targets and their properties
table4.dat 70 108 Targets and their photometric redshift properties
table5.dat 113 108 Signpost galaxies and their photometric
properties
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See also:
VIII/95 : Herschel Multi-tiered Extragalactic Survey (Oliver+, 2012)
J/ApJ/563/629 : VIK' photo and redshifts of galaxy clusters (Nelson+, 2001)
J/ApJ/622/772 : Redshift survey of submillimeter galaxies (Chapman+, 2005)
J/ApJ/621/673 : Line indices for 124 early-type galaxies (Thomas+, 2005)
J/AJ/131/1288 : Composite spectra of early-type galaxies (Bernardi+, 2006)
J/MNRAS/372/1621 : SCUBA Half-Degree Extragalactic Survey. II (Coppin+, 2006)
J/MNRAS/380/199 : SCUBA Half-Degree Extragalactic Survey. III (Ivison+, 2007)
J/ApJ/704/548 : Photometric prop of galaxies at z=4-6 (Overzier+, 2009)
J/ApJ/707/1201 : LABOCA ECDFS Submillimeter Survey (LESS) (Weiss+, 2009)
J/A+A/513/A53 : LABOCA 870um images of evolved stars (Ladjal+, 2010)
J/ApJ/719/763 : Millimeter-wave sources in the SPT survey (Vieira+, 2010)
J/A+A/527/A145 : Chamaeleon I 870um sources (Belloche+, 2011)
J/MNRAS/413/2314 : Radio & mid-IR counterpart of submm galaxies (Biggs+, 2011)
J/A+A/542/A101 : LABOCA 870um map 4 Galactic plane fields (Miettinen, 2012)
J/MNRAS/436/1919 : SCUBA observations of COSMOS galaxies (Casey+, 2013)
J/A+A/570/A55 : Spiderweb galaxy 870um & 1.4GHz images (Dannerbauer+, 2014)
J/ApJ/783/84 : ALMA obs in 107 galaxies at z=0.2-2.5 (Scoville+, 2014)
J/ApJ/788/125 : ALMA survey of ECDFS submillimeter galaxies (Simpson+,2014)
J/ApJ/812/43 : ALMA 870um obs. of HerMES galaxies (Bussmann+, 2015)
J/MNRAS/462/1989 : HerMES Large Mode Survey catalogue (Asboth+, 2016)
J/MNRAS/462/3146 : Herschel-ATLAS DR1 (HATLAS) (Valiante+, 2016)
J/MNRAS/465/1789 : SCUBA-2 Cosmology Legacy Survey (Geach+, 2017)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Target Target name
13- 14 I2 h RAh Hour of right ascension (J2000)
16- 17 I2 min RAm Minute of right ascension (J2000)
19- 23 F5.2 s RAs Second of right ascension (J2000)
25 A1 --- DE- Sign of declination (J2000)
26- 27 I2 deg DEd Degree of declination (J2000)
29- 30 I2 arcmin DEm Arcminute of declination (J2000)
32- 35 F4.1 arcsec DEs Arcsecond of declination (J2000)
37- 40 F4.1 h Tint [0.5/16.6] Integration time
42- 44 F3.1 --- tau [0.2/0.4] Average opacity value (τ)
46- 48 F3.1 mJy/beam sigma [1.7/8] Average sensitivity of the map
(σ) (1)
50- 52 I3 arcmin2 Omega [112/137] Extent of LABOCA map (Ω)
54- 61 A8 "Y/M" Date Date of observation
63- 92 A30 --- PID Program identifier
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Note (1): Average depth computed across each beam-smoothed LABOCA map, where
the resulting FWHM of a beam is 27".
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Target Target name
13- 34 A22 --- ID Name of the dusty star-forming galaxy (G1)
36 A1 --- f_zphot [b] Flag on zphot (1)
38- 40 F3.1 --- zphot [0.9/7.3]? Photometric redshift
42- 44 F3.1 --- e_zphot [0.1/4.1]? Lower error on redshift (2)
46- 48 F3.1 --- E_zphot [0.1/6.3]? Upper error on redshift (2)
50- 54 F5.2 --- Chi2 [0.01/33]? χ2 value
56- 60 F5.2 [Lsun] logLfir [11/14]? log of FIR luminosity
62- 65 F4.2 [Lsun] e_logLfir [0.02/1.3]? Lower error on logLfir
67- 70 F4.2 [Lsun] E_logLfir [0.02/1]? Upper error on LogLfir
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Note (1): Flags as follow :
b = SPIRE non-detections for which we do not provide any photometric
redshifts; we do not include these in our analysis.
Note (2): We quote errors based on χ2+1 values, without the adding the
intrinsic template scatter in quadrature.
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Target Target name
13- 34 A22 --- ID Name of the dusty star-forming galaxy (G1)
36- 38 A3 --- n_ID [b,t ] Flag(s) on ID (1)
40- 41 I2 h RAh Hour of right ascension (J2000)
43- 44 I2 min RAm Minute of right ascension (J2000)
46- 50 F5.2 s RAs Second of right ascension (J2000)
52 A1 --- DE- Sign of declination (J2000)
53- 54 I2 deg DEd Degree of declination (J2000)
56- 57 I2 arcmin DEm Arcminute of declination (J2000)
59- 62 F4.1 arcsec DEs Arcsecond of declination (J2000)
64- 67 F4.1 mJy/beam S250 [-4/97.2] Herschel/SPIRE 250um peak
flux density (2)
69- 72 F4.1 mJy/beam e_S250 [5.1/11.5] Error on S250
74- 78 F5.1 mJy/beam S350 [-9/106] Herschel/SPIRE 350um peak
flux density (2)
80- 83 F4.1 mJy/beam e_S350 [6.1/12] Error on S350
85- 89 F5.1 mJy/beam S500 [-15.2/125] Herschel/SPIRE 500um peak
flux density (2)
91- 94 F4.1 mJy/beam e_S500 [6.8/12.5] Error on S500
96- 99 F4.1 mJy/beam S870 [3.2/81.7] LABOCA 870um peak flux density (2)
101-103 F3.1 mJy/beam e_S870 [1.1/8.4] Error on S870
105-108 F4.2 --- B [1/7.7]? Mean flux boosting parameter (3)
110-113 F4.2 --- F [0.5/1]? Mean fidelity parameter (4)
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Note (1): Flag as follows:
b = Signpost ultra-red galaxies that are undetected. We report the
peak flux density and rms values for these sources within a 45"
aperture centered on the telescope pointing position. We do not
provide flux-boosting (B) or fidelity (F) values.
t = Target. Each source detected in a given field is subsequently listed
in increasing order of detected S/N.
Note (2): SPIRE flux densities have been boosted to reflect the radial
offset of a LABOCA source. Additionally, 870µm flux densities have
been deboosted.
Note (3): The flux boosting, B, i.e., the ratio of recovered to input
flux densities. See section 3 for further explanations.
Note (4): We chose a detection threshold (Σthresh) based on the values
of a "fidelity" or "trustworthiness" parameter, F, similar to that
outlined in Aravena+ (2016ApJ...833...68A 2016ApJ...833...68A). See Equation (1):
F=1-Njack/N where N is the number of sources detected in our maps
and Njack is the mean number of sources detected in our 100
jackknife realizations for each map.
See section 3 for further explanations.
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Global notes:
Note (G1): Names based on coordinates; objects with missing "0" in RA
and/or DEC have been corrected at CDS.
Galaxies are <[LIB2018] LURGS JHHMMSS.s+DDMMSS> for Simbad.
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History:
From electronic version of the journal
References:
Ivison et al. Paper I. 2016ApJ...832...78I 2016ApJ...832...78I
(End) Coralie FIX [CDS] 24-Oct-2019