J/ApJ/810/107 Lyman break galaxies and LAEs HST photometry (Mostardi+, 2015)
A high-resolution Hubble Space Telescope study of apparent Lyman continuum
leakers at z∼3.
Mostardi R.E., Shapley A.E., Steidel C.C., Trainor R.F., Reddy N.A.,
Siana B.
<Astrophys. J., 810, 107 (2015)>
=2015ApJ...810..107M 2015ApJ...810..107M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Photometry, HST ; Redshifts
Keywords: cosmology: observations - diffuse radiation -
galaxies: high-redshift - intergalactic medium
Abstract:
We present U336V606J125H160 follow-up Hubble Space Telescope
(HST) observations of 16 z∼3 candidate Lyman continuum (LyC)
emitters in the HS1549+1919 field. With these data, we obtain high
spatial-resolution photometric redshifts of all sub-arcsecond
components of the LyC candidates in order to eliminate foreground
contamination and identify robust candidates for leaking LyC emission.
Of the 16 candidates, we find one object with a robust LyC detection
that is not due to foreground contamination. This object (MD5)
resolves into two components; we refer to the LyC-emitting component
as MD5b. MD5b has an observed 1500 Å to 900 Å flux-density ratio
of (FUV/FLyC)obs=4.0±2.0, compatible with predictions from
stellar population synthesis models. Assuming minimal IGM absorption,
this ratio corresponds to a relative (absolute) escape fraction of
fesc,relMD5b=75%-100% (fesc,absMD5b=14%-19%). The stellar
population fit to MD5b indicates an age of ≲50 Myr, which is in the
youngest 10% of the HST sample and the youngest third of typical z∼3
Lyman break galaxies, and may be a contributing factor to its LyC
detection. We obtain a revised, contamination-free estimate for the
comoving specific ionizing emissivity at z=2.85, indicating (with
large uncertainties) that star-forming galaxies provide roughly the
same contribution as QSOs to the ionizing background at this redshift.
Our results show that foreground contamination prevents ground-based
LyC studies from obtaining a full understanding of LyC emission from z∼3
star-forming galaxies. Future progress in direct LyC searches is
contingent upon the elimination of foreground contaminants through
high spatial-resolution observations, and upon acquisition of
sufficiently deep LyC imaging to probe ionizing radiation in
high-redshift galaxies.
Description:
The HS1549 galaxy sample discussed in Mostardi et al. (2013ApJ...779...65M 2013ApJ...779...65M)
consists of 49 LBGs and 91 LAEs, all spectroscopically confirmed at
z≥2.82. There are 9 objects part of both the LAE and LBG samples;
for simplicity in displaying our data, we group these objects with the
LBGs. The redshift limit of z≥2.82 ensures that the NB3420 filter
is sensitive only to LyC emission, with no contamination from flux
redward of the Lyman limit. Out of these galaxies, 5 LBGs and 7 LAEs
have NB3420 detections within 1.9" of the non-ionizing UV (∼1500 Å)
centroid of the galaxy, indicating potential LyC emission if there
is no lower-redshift galaxy contaminant along the line of sight.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 121 47 LBG and LAE Photometry
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See also:
J/ApJ/592/728 : Lyman break galaxies at redshift z∼3 (Steidel+, 2003)
J/A+A/461/823 : Candidate Lyα emitting galaxies (Venemans+, 2007)
J/A+A/498/13 : Lyman-α emitters from redshifts z∼2-3 (Nilsson+, 2009)
J/ApJ/765/47 : Lyman-break galaxies and LAEs at z∼3 (Nestor+, 2013)
J/MNRAS/430/425 : VLT LBG Redshift Survey. III. (Bielby+, 2013)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- ID Object identifier (1)
10- 11 I2 h RAh Hour of Right Ascension (J2000) (2)
13- 14 I2 min RAm Minute of Right Ascension (J2000) (2)
16- 21 F6.3 s RAs Second of Right Ascension (J2000) (2)
22 A1 --- DE- Sign of the Declination
23- 24 I2 deg DEd Degree of Declination (J2000) (2)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000) (2)
29- 34 F6.3 arcsec DEs Arcsecond of Declination (J2000) (2)
36 A1 --- l_U336 [>] Limit flag on U336
37- 41 F5.2 mag U336 HST WFC3/UVIS isophotal magnitude U336 (AB)
42 A1 --- n_U336 [g] Note on U336 (3)
44- 47 F4.2 mag E_U336 ? Upper 3σ limit uncertainty in U336
49- 52 F4.2 mag e_U336 ? Lower 3σ limit uncertainty in U336
54- 58 F5.2 mag V606 HST ACS/WFC isophotal magnitude V606 (AB)
60- 63 F4.2 mag E_V606 Upper 3σ limit uncertainty in V606
65- 68 F4.2 mag e_V606 Lower 3σ limit uncertainty in V606
70 A1 --- l_J125 [>] Limit flag on J125
71- 75 F5.2 mag J125 HST WFC3/IR isophotal magnitude J125 (AB)
77- 80 F4.2 mag E_J125 ? Upper 3σ limit uncertainty in J125
82- 85 F4.2 mag e_J125 ? Lower 3σ limit uncertainty in J125
87 A1 --- l_H160 [>] Limit flag on H160
88- 92 F5.2 mag H160 HST WFC3/IR isophotal magnitude H160 (AB)
94- 97 F4.2 mag E_H160 ? Upper 3σ limit uncertainty in H160
99-102 F4.2 mag e_H160 ? Lower 3σ limit uncertainty in H160
104-108 F5.3 --- zspec ? Spectroscopic redshift (4)
109 A1 --- n_zspec [f] Note on zspec (5)
111-114 F4.2 --- zPEG PEGASE photometric redshift
116-119 F4.2 --- zBPASS BPASS photometric redshift
121 A1 --- Type [acr-] SED type (6)
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Note (1): Objects are listed by their IDs from Mostardi et al.
(2013ApJ...779...65M 2013ApJ...779...65M). The final letter of the object name indicates
the sub-arcsecond component of the galaxy, according to the labels in
Figures 3, 4, and 5.
Note (2): Object centroids calculated from V606.
Note (3): Note as follows:
g = Although MD5b is formally undetected in U336 at 3σ, emission at
the location of MD5b is visible by eye in the U336 imaging. This emission
corresponds to a 2.25σ detection in
U336(m336=27.37-0.40+0.64), which is consistent within errors of
the detection in NB3420 (mNB3420=26.89-0.31+0.43).
Note (4): Spectroscopic redshifts listed were obtained via ground-based
spectroscopy, and thus in general it is not possible to distinguish
between individual sub-arcsecond components of galaxies within the
spectrum. We list spectroscopic redshifts only when the SED fit
indicates that the object is not a foreground contaminant.
Spectroscopic redshifts are not listed for the following types of
objects: LAEs without spectroscopic follow-up, contaminants identified
via photometric redshifts, and objects where U336V606J125H160
photometric data were insufficient to determine a photometric
redshift.
Note (5): Note as follows:
f = The original Lyα redshift associated with lae2436 from
Mostardi et al. (2013ApJ...779...65M 2013ApJ...779...65M) was z=2.832. Subsequent reanalysis
of the available spectra near this object indicates that the z=2.832
emission was associated with a nearby Lyα blob (see Section 5.3.1).
Note (6): Type as follows:
a = Ambiguous SED shape, defined in Section 5.1;
c = The SED of the object implies a foreground contaminant;
r = The SED of the object implies a real z∼2.85 galaxy.
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History:
From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 03-Oct-2017