J/ApJ/793/115 UV-continuum slopes beta for z∼4-8 galaxies (Bouwens+, 2014)
UV-continuum slopes of >4000 z∼4-8 galaxies from the HUDF/XDF, HUDF09, ERS,
CANDELS-south, and CANDELS-north fields.
Bouwens R.J., Illingworth G.D., Oesch P.A., Labbe I., van Dokkum P.G.,
Trenti M., Franx M., Smit R., Gonzalez V., Magee D.
<Astrophys. J., 793, 115 (2014)>
=2014ApJ...793..115B 2014ApJ...793..115B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Photometry, HST ; Photometry, ultraviolet ;
Redshifts
Keywords: galaxies: evolution; galaxies: high-redshift
Abstract:
We measure the UV-continuum slope β for over 4000 high-redshift
galaxies over a wide range of redshifts z∼4-8 and luminosities from
the HST HUDF/XDF, HUDF09-1, HUDF09-2, ERS, CANDELS-N, and CANDELS-S
data sets. Our new β results reach very faint levels at z∼4
(-15.5 mag: 0.006 Lz=3*), z∼5 (-16.5 mag: 0.014 Lz=3*), and
z∼6 and z∼7 (-17 mag: 0.025 Lz=3*). Inconsistencies between
previous studies led us to conduct a comprehensive review of
systematic errors and develop a new technique for measuring β
that is robust against biases that arise from the impact of noise. We
demonstrate, by object-by-object comparisons, that all previous
studies, including our own and those done on the latest HUDF12 data
set, suffered from small systematic errors in β. We find that
after correcting for the systematic errors (typically
Δβ∼0.1-0.2) all β results at z∼7 from different
groups are in excellent agreement. The mean β we measure for
faint (-18 mag: 0.1Lz=3*) z∼4, z∼5, z∼6, and z∼7 galaxies
is -2.03±0.03±0.06 (random and systematic errors),
-2.14±0.06±0.06, -2.24±0.11±0.08, and -2.30±0.18±0.13,
respectively. Our new β values are redder than we have reported
in the past, but bluer than other recent results. Our previously
reported trend of bluer β's at lower luminosities is confirmed,
as is the evolution to bluer β's at high redshifts. β
appears to show only a mild luminosity dependence faintward of
M_UV, AB_~-19 mag, suggesting that the mean β asymptotes to
~-2.2 to -2.4 for faint z≥4 galaxies. At z∼7, the observed
β's suggest non-zero, but low dust extinction, and they agree
well with values predicted in cosmological hydrodynamical simulations.
Description:
To accurately quantify the UV-continuum slope of galaxies as a
function of luminosity, we require observations over a wide range in
depths. These include both the very deep observations over the XDF
that extend to very faint luminosities in 9 bands from B435 to H160
and the deep, wide-area observations over CANDELS that provide
statistically useful samples of the rarer bright galaxies. Our deepest
data set, the ∼4.7 arcmin2 XDF, incorporates all available WFC3/IR
observations from the HUDF09, HUDF12, and CANDELS programs, including
∼100 orbit Y105-band, ∼40 orbit J125-band, 30 orbit JH140-band, and
∼85 orbit H160-band observations. Importantly, the current XDF data
set includes all of the available observations in the J125 and H160
bands over the HUDF, thereby providing the strongest possible
constraints on the UV-continuum slopes β of star-forming galaxies at
z∼4-8.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table8.dat 67 4213 A complete list of the UV-continuum slopes beta
measures for sources in our z∼4, z∼5, z∼6,
z∼7, and z∼8 samples
table9.dat 102 4213 Complete set of flux measurements used to
derive beta for our z∼4, z∼5, z∼6, z∼7,
and z∼8 samples
--------------------------------------------------------------------------------
See also:
J/ApJ/653/53 : z∼6 galaxies UV luminosity function (Bouwens+, 2006)
J/AJ/141/14 : HST WFC3 ERS : emission-line galaxies (Straughn+, 2011)
J/ApJ/743/146 : HST/WFC3 observations in HUDF and GOODS-S (Cameron+, 2011)
J/ApJ/756/164 : UV galaxies in CANDELS from z=8 to z=4 (Finkelstein+, 2012)
J/MNRAS/453/1136 : XDF CHEF photometric catalogue (Jimenez-Teja+, 2015)
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- ID Source ID
22- 23 I2 h RAh Hour of Right Ascension (J2000)
25- 26 I2 min RAm Minute of Right Ascension (J2000)
28- 32 F5.2 s RAs Second of Right Ascension (J2000)
34 A1 --- DE- Sign of the Declination (J2000)
35- 36 I2 deg DEd Degree of Declination (J2000)
38- 39 I2 arcmin DEm Arcminute of Declination (J2000)
41- 45 F5.2 arcsec DEs Arcsecond of Declination (J2000)
47- 52 F6.2 mag UVMag Absolute AB magnitude in the Rest-frame UV
54- 58 F5.2 --- beta UV-continuum slope beta
60- 63 F4.2 --- e_beta Uncertainty in the UV-continuum slope beta
65 I1 --- rset [4/8] Sample (1)
67 I1 --- dset [1/4] Data Set (2)
--------------------------------------------------------------------------------
Note (1): The mean redshift of the sample in which the source was found.
Note (2): The data set from which the source was selected and in which its
UV-continuum slope beta was derived. Referenced as follows:
1 = HUDF/XDF (Illingworth et al. 2013ApJS..209....6I 2013ApJS..209....6I);
2 = HUDF09-1 (Bouwens et al. 2011ApJ...737...90B 2011ApJ...737...90B);
3 = HUDF09-2 (Bouwens et al. 2011ApJ...737...90B 2011ApJ...737...90B);
4 = CANDELS/ERS (Grogin et al. 2011ApJS..197...35G 2011ApJS..197...35G ; Koekemoer et al.
2011ApJS..197...36K 2011ApJS..197...36K ; Windhorst et al. 2011ApJS..193...27W 2011ApJS..193...27W).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- ID Source ID
23- 27 I5 --- iflux ? F775W Flux Measurement; 100 pJy
29- 31 I3 --- e_iflux ? Uncertainty in iflux
33- 37 I5 --- Iflux ? F814W Flux Measurement; 100 pJy
39- 42 I4 --- e_Iflux ? Uncertainty in Iflux
44- 48 I5 --- zflux ? F850LP Flux Measurement; 100 pJy
50- 52 I3 --- e_zflux ? Uncertainty in zflux
54- 58 I5 --- yflux ? F098M Flux Measurement; 100 pJy
60- 62 I3 --- e_yflux ? Uncertainty in yflux
64- 68 I5 --- Yflux ? F105W Flux Measurement; 100 pJy
70- 72 I3 --- e_Yflux ? Uncertainty in Yflux
74- 78 I5 --- Jflux ? F125W Flux Measurement; 100 pJy
80- 82 I3 --- e_Jflux ? Uncertainty in Jflux
84- 88 I5 --- JHflux ? F140W Flux Measurement; 100 pJy
90- 92 I3 --- e_JHflux ? Uncertainty in JHflux
94- 98 I5 --- Hflux ? F160W Flux Measurement; 100 pJy
100-102 I3 --- e_Hflux ? Uncertainty in Hflux
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 19-Apr-2017