J/ApJ/800/18 HST/WFC3 observations of z∼7-8 galaxies in A2744 (Atek+, 2015)
New constraints on the faint end of the UV luminosity function at z∼7-8 using
the gravitational lensing of the Hubble frontier fields cluster A2744.
Atek H., Richard J., Kneib J.-P., Jauzac M., Schaerer D., Clement B.,
Limousin M., Jullo E., Natarajan P., Egami E., Ebeling H.
<Astrophys. J., 800, 18 (2015)>
=2015ApJ...800...18A 2015ApJ...800...18A
ADC_Keywords: Galaxies, IR ; Photometry, HST ; Redshifts ; Clusters, galaxy ;
Gravitational lensing
Keywords: galaxies: evolution; galaxies: high-redshift;
galaxies: luminosity function, mass function;
gravitational lensing: strong
Abstract:
Exploiting the power of gravitational lensing, the Hubble Frontier
Fields (HFF) program aims at observing six massive galaxy clusters to
explore the distant universe far beyond the limits of blank field
surveys. Using the complete Hubble Space Telescope observations of the
first HFF cluster A2744, we report the detection of 50 galaxy
candidates at z∼7 and eight candidates at z∼8 in a total survey area
of 0.96arcmin2 in the source plane. Three of these galaxies are
multiply imaged by the lensing cluster. Using an updated model of the
mass distribution in the cluster we were able to calculate the
magnification factor and the effective survey volume for each galaxy
in order to compute the ultraviolet galaxy luminosity function (LF) at
both redshifts 7 and 8. Our new measurements reliably extend the z∼7
UV LF down to an absolute magnitude of MUV~-15.5. We find a
characteristic magnitude of MUV*=-20.90-0.73+0.90mag and a
faint-end slope α=-2.01-0.28+0.20, close to previous
determinations in blank fields. We show here for the first time that
this slope remains steep down to very faint luminosities of 0.01L*.
Although prone to large uncertainties, our results at z∼8 also seem to
confirm a steep faint-end slope below 0.1L*. The HFF program is
therefore providing an extremely efficient way to study the faintest
galaxy populations at z>7 that would otherwise be inaccessible with
current instrumentation. The full sample of six galaxy clusters will
provide even better constraints on the buildup of galaxies at early
epochs and their contribution to cosmic reionization.
Description:
These HST observations are part of the HFF program (GO/DD 13495) and
include NIR and optical data centered on the cluster A2744 at
RAJ2000=00:14:21.2, DEJ2000=-30:23:50.1. NIR imaging includes the four
bands of WFC3: F105W, F125W, F140W, and F160W, and was obtained during
2013 October and November for a total of 24, 12, 10, and 24 orbits,
respectively. The second epoch observations of A2744 started in 2014
May to obtain ACS imaging in F435W, F606W, and F814W filters for a
total of 18, 10, and 42 orbits, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 82 50 Photometric and color measurements for
the z∼6-7 dropouts
table4.dat 80 8 Photometric and color measurements for
the z∼8 dropouts
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/578/A105 : EELGs out to z∼1 in zCOSMOS (Amorin+, 2015)
J/MNRAS/443/1549 : MACSJ0416.1-2403 strong-lensing analysis (Jauzac+, 2014)
J/MNRAS/440/2810 : Galaxy luminosity function at z ≃ 7 (Bowler+, 2014)
J/ApJ/765/47 : Lyman-break galaxies and LAEs at z∼3 (Nestor+, 2013)
J/ApJ/762/L30 : CLASH: MCS J0416.1-2403 strong lensing analysis (Zitrin+, 2013)
J/ApJ/738/69 : SEDs of galaxies at 3.8<z<5 in GOODS (Shim+, 2011)
J/ApJ/728/27 : Chandra and AAOmega observations of Abell 2744 (Owers+, 2011)
J/A+A/500/947 : Spectroscopy and photometry in A2744 and A2537 (Braglia+, 2009)
J/ApJ/668/643 : Multiply imaged gravitational lens systems (Limousin+, 2007)
J/ApJ/653/53 : z∼6 galaxies UV luminosity function (Bouwens+, 2006)
J/ApJ/627/32 : Gravitationally lensed arcs in HST WFPC2 archive (Sand+, 2005)
J/AJ/120/2747 : HDF-South WFPC2 observations (Casertano+, 2000)
http://www.stsci.edu/hst/campaigns/frontier-fields/FF-Data : Frontier Fields
HST data
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- [ARK2015] [260/6670] Target number
6- 14 F9.7 deg RAdeg Right ascension in decimal degrees (J2000)
16- 25 F10.6 deg DEdeg Declination in decimal degrees (J2000)
27 A1 --- l_I-Y Limit flag on I-Y
29- 32 F4.2 mag I-Y [0.8/3.6] HST I814-Y105 color index
34- 37 F4.2 mag e_I-Y [0.05/0.7]? I-Y uncertainty
39- 43 F5.2 mag Y-J [-0.5/0.8] HST/WFC3 Y105-J125 color index
45- 48 F4.2 mag e_Y-J [0.01/0.6] Y-J uncertainty
50- 54 F5.2 mag Jmag [24/29.3] HST/WFC3 F125W (J125) AB magnitude
56- 59 F4.2 mag e_Jmag [0.01/0.5] Jmag uncertainty
61- 65 F5.2 --- Mag [1.7/30] Magnification (flux amplification
factor)
67- 70 F4.2 --- z [5.4/7.4] Photometric redshift
72- 76 F5.3 --- b_z [3/7] 68% lower limit on z
78- 82 F5.3 --- B_z [5/8] 68% upper limit on z
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- [ARK2015] [1060/6593] Target number
6- 14 F9.7 deg RAdeg Right ascension in decimal degrees (J2000)
16- 25 F10.6 deg DEdeg Declination in decimal degrees (J2000)
27- 30 F4.2 mag Y-J [0.5/1.5] HST/WFC3 Y105-J125 color index
32- 35 F4.2 mag e_Y-J [0.1/0.5] Y-J uncertainty
37- 41 F5.2 mag J-H [-0.4/0.3] HST/WFC3 J125-H140 color index
43- 46 F4.2 mag e_J-H [0.08/0.4] J-H uncertainty
48- 52 F5.2 mag Hmag [25/29] HST/WFC3 F140W (H140) AB magnitude
54- 57 F4.2 mag e_Hmag [0.05/0.3] Hmag uncertainty
59- 63 F5.2 --- Mag [1.8/16.5] Magnification (flux amplification
factor)
65- 68 F4.2 --- z [7.3/8] Photometric redshift
70- 74 F5.3 --- b_z [6/8] 68% lower limit on z
76- 80 F5.3 --- B_z [7/9] 68% upper limit on z
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 29-Jun-2015