16 research outputs found
Slicing COSMOS with SC4K:the evolution of typical Lya emitters and the Lya escape fraction from z~2 to z~6
We present and explore deep narrow- and medium-band data obtained with the Subaru and the Isaac Newton telescopes in the ~2 deg COSMOS field. We use these data as an extremely wide, low-resolution (R~20-80) IFU survey to slice through the COSMOS field and obtain a large sample of ~4000 Lyman- (Lya) emitters from z~2 to z~6 in 16 redshift slices (SC4K). We present new Lya luminosity functions (LFs) covering a co-moving volume of ~10Mpc. SC4K extensively complements ultra-deep surveys, jointly covering over 4 dex in Lya luminosity and revealing a global (2.5z 3.5, likely linked with the evolution of the AGN population. The Lya luminosity density rises by a factor ~2 from z~2 to z~3 but is then found to be roughly constant (~ erg s Mpc) to z~6, despite the ~0.7 dex drop in UV luminosity density. The Lya/UV luminosity density ratio rises from % to % from z~2.2 to z~6. Our results imply a rise of a factor of ~2 in the global ionisation efficiency () and a factor ~ in the Lya escape fraction from z~2 to z~6, hinting for evolution in both the typical burstiness/stellar populations and even more so in the typical ISM conditions allowing Ly photons to escape
Exploring the Correlation between -to-UV Ratio and Burstiness for Typical Star-forming Galaxies at
The -to-UV luminosity ratio () is
often used to probe SFHs of star-forming galaxies and it is important to
validate it against other proxies for burstiness. To address this issue, we
present a statistical analysis of the resolved distribution of
as well as stellar age and their correlations with the
globally measured for a sample of 310 star-forming
galaxies in two redshift bins of and
observed by the MOSDEF survey. We use the multi-waveband CANDELS/3D-HST imaging
of MOSDEF galaxies to construct and stellar age maps. We
analyze the composite rest-frame far-UV spectra of a subsample of MOSDEF
targets obtained by the Keck/LRIS, which includes 124 star-forming galaxies
(MOSDEF-LRIS) at redshifts , to examine the average stellar
population properties, and the strength of age-sensitive FUV spectral features
in bins of . Our results show no significant evidence
that individual galaxies with higher are undergoing
a burst of star formation based on the resolved distribution of
of individual star-forming galaxies. We segregate the
sample into subsets with low and high . The
high- subset exhibits, on average, an age of
= 8.0, compared to = 8.4 for the
low- galaxies, though the difference in age is
significant at only the level. Furthermore, we find no variation in
the strengths of Siiv and Civ P-Cygni features from massive stars between the two subsamples.Comment: 16 pages, 10 figures, published by the Monthly Notices of the Royal
Astronomical Societ
A comprehensive study of H emitters at 0.62 in the DAWN survey: the need for deep and wide regions
We present new estimates of the luminosity function (LF) and star formation
rate density (SFRD) for an H selected sample at from the
Deep And Wide Narrow-band (DAWN) survey. Our results are based on a new
H sample in the extended COSMOS region (compared to Coughlin et al.
2018) with the inclusion of flanking fields, resulting in a total area coverage
of 1.5 deg. A total of 241 H emitters were selected based on
robust selection criteria using spectro-photometric redshifts and broadband
color-color classification. We explore the effect of different dust correction
prescriptions by calculating the LF and SFRD using a constant dust extinction
correction, A{} mag, a luminosity-dependent correction,
and a stellar-mass dependent correction. The resulting H LFs are well
fitted using Schechter functions with best-fit parameters: L erg
s, Mpc, for constant dust
correction, L erg s, Mpc,
for luminosity-dependent dust correction, and L
erg s, Mpc, , for stellar
mass-dependent dust correction. The deep and wide nature of the DAWN survey
effectively samples H emitters over a wide range of luminosities,
thereby providing better constraints on both the faint and bright end of the
LF. Also, the SFRD estimates
MyrMpc (constant dust correction),
MyrMpc
(luminosity-dependent dust correction), and
MyrMpc (stellar mass-dependent dust correction) are in
good agreement with the evolution of SFRD across redshifts () seen
from previous H surveys.Comment: 16 pages, 8 figures, Accepted for publication in Ap
CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey - The Hubble Space Telescope Observations, Imaging Data Products and Mosaics
This paper describes the Hubble Space Telescope imaging data products and
data reduction procedures for the Cosmic Assembly Near-IR Deep Extragalactic
Legacy Survey (CANDELS). This survey is designed to document the evolution of
galaxies and black holes at , and to study Type Ia SNe beyond
. Five premier multi-wavelength sky regions are selected, each with
extensive multiwavelength observations. The primary CANDELS data consist of
imaging obtained in the Wide Field Camera 3 / infrared channel (WFC3/IR) and
UVIS channel, along with the Advanced Camera for Surveys (ACS). The
CANDELS/Deep survey covers \sim125 square arcminutes within GOODS-N and
GOODS-S, while the remainder consists of the CANDELS/Wide survey, achieving a
total of \sim800 square arcminutes across GOODS and three additional fields
(EGS, COSMOS, and UDS). We summarize the observational aspects of the survey as
motivated by the scientific goals and present a detailed description of the
data reduction procedures and products from the survey. Our data reduction
methods utilize the most up to date calibration files and image combination
procedures. We have paid special attention to correcting a range of
instrumental effects, including CTE degradation for ACS, removal of electronic
bias-striping present in ACS data after SM4, and persistence effects and other
artifacts in WFC3/IR. For each field, we release mosaics for individual epochs
and eventual mosaics containing data from all epochs combined, to facilitate
photometric variability studies and the deepest possible photometry. A more
detailed overview of the science goals and observational design of the survey
are presented in a companion paper.Comment: 39 pages, 25 figure
The Interstellar Medium in [O iii]-selected Star-forming Galaxies at z ∼ 3.2
We present new results from near-infrared spectroscopy with Keck/MOSFIRE of [O III]-selected galaxies at z ~ 3.2. With our H and K band spectra, we investigate the interstellar medium (ISM) conditions, such as ionization states and gas metallicities. [O III] emitters at z ~ 3.2 show a typical gas metallicity of 12 log O H 8.07 0.07 + = ( ) at * log 9.0 9. () – M M ~ 2 and 12 log O H 8.31 0.04 + = ( ) at * log 9.7 10.2 () – M M ~ when using the empirical calibration method. We compare the [O III] emitters at z ~ 3.2 with UV-selected galaxies and Lyα emitters at the same epoch and find that the [O III]-based selection does not appear to show any systematic bias in the selection of star-forming galaxies. Moreover, comparing with star-forming galaxies at z ~ 2 from the literature, our samples show similar ionization parameters and gas metallicities as those obtained by the previous studies that used the same calibration method. We find no strong redshift evolution in the ISM conditions between z ~ 3.2 and z ~ 2. Considering that the star formation rates at a fixed stellar mass also do not significantly change between the two epochs, our results support the idea that the stellar mass is the primary quantity to describe the evolutionary stages of individual galaxies at z > 2