13 research outputs found
A selection of H{\alpha} emitters at z = 2.1-2.5 using the Ks-band photometry of ZFOURGE
Large and less-biased samples of star-forming galaxies are essential to
investigate galaxy evolution. H{\alpha} emission line is one of the most
reliable tracers of star-forming galaxies because its strength is directly
related to recent star formation. However, it is observationally expensive to
construct large samples of H{\alpha} emitters by spectroscopic or narrow-band
imaging survey at high-redshifts. In this work, we demonstrate a method to
extract H{\alpha} fluxes of galaxies at z = 2.1-2.5 from Ks broad-band
photometry of ZFOURGE catalog. Combined with 25-39 other filters, we estimate
the emission line fluxes by SED fitting with stellar population models that
incorporate emission-line strengths. 2005 galaxies are selected as H{\alpha}
emitters by our method and their fluxes show good agreement with previous
measurements in the literature. On the other hand, there are more H{\alpha}
luminous galaxies than previously reported. The discrepancy can be explained by
extended H{\alpha} profiles of massive galaxies and a luminosity dependence of
dust attenuation, which are not taken into account in the previous work. We
also find that there are a large number of low-mass galaxies with much higher
specific star formation rate (sSFR) than expected from the extrapolated star
formation main sequence. Such low-mass galaxies exhibit larger ratios between
H{\alpha} and UV fluxes compared to more massive high sSFR galaxies. This
result implies that a "starburst" mode may differ among galaxies: low-mass
galaxies appear to assemble their stellar mass via short-duration bursts while
more massive galaxies tend to experience longer-duration (> 10 Myr) bursts.Comment: 18 pages, 19 figures, Resubmitted to ApJ after addressing reviewer's
comment
Multiple emission lines of H emitters at from the broad and medium-band photometry in the ZFOURGE Survey
We present a multiple emission lines study of 1300 H emitters
(HAEs) at in the ZFOURGE survey. In contrast to the traditional
spectroscopic method, our sample is selected based on the flux excess in the
ZFOURGE- broad-band data relative to the best-fit stellar continuum. Using
the same method, we also extract the strong diagnostic emission lines for these
individual HAEs: [OIII],
[OII]. Our measurements exhibit good consistency with
those obtained from spectroscopic surveys. We investigate the relationship
between the equivalent widths (EWs) of these emission lines and various galaxy
properties, including stellar mass, stellar age, star formation rate (SFR),
specific SFR (sSFR), ionization states (O32). We have identified a discrepancy
between between HAEs at and typical local star-forming galaxy
observed in the SDSS, suggesting the evolution of lower gas-phase metallicity
() and higher ionization parameters () with redshift. Notably, we have
observed a significant number of low-mass HAEs exhibiting exceptionally high
. Their galaxy properties are comparable to those of
extreme objects, such as extreme O3 emitters (O3Es) and Ly emitters
(LAEs) at . Considering that these characteristics may indicate
potential strong Lyman continuum (LyC) leakage, higher redshift anaglogs of the
low-mass HAEs could be significant contributors to the cosmic reionization.
Further investigations on this particular population are required to gain a
clearer understanding of galaxy evolution and cosmic reionization.Comment: 24 pages, 13 figures, submitted to Ap
Environmental impact on star-forming galaxies in a cluster during course of galaxy accretion
Galaxies change their properties as they assemble into clusters. In order to
understand the physics behind that, we need to go back in time and observe
directly what is occurring in galaxies as they fall into a cluster. We have
conducted a narrow-band and -band imaging survey on a cluster CL1604-D at
using a new infrared instrument SWIMS installed at the Subaru
Telescope. The narrow-band filter, NB1261, matches to H emission from
the cluster at . Combined with a wide range of existing data from
various surveys, we have investigated galaxy properties in and around this
cluster in great detail. We have identified 27 H emitters associated
with the cluster. They have significant overlap with MIPS 24m sources and
are located exclusively in the star forming regime on the rest-frame
diagram. We have identified two groups of galaxies near the cluster in the 2D
spatial distribution and the phase-space diagram, which are likely to be
in-falling to the cluster main body. We have compared various physical
properties of star forming galaxies, such as specific star formation rates
(burstiness) and morphologies (merger) as a function of environment; cluster
center, older group, younger group, and the field. As a result, a global
picture has emerged on how the galaxy properties are altered as they assemble
into a denser region. This includes the occurrence of mergers, enhancement of
star formation activity, excursion to the dusty starburst phase, and eventual
quenching to a passive phase.Comment: 19 pages, 15 figures. Accepted for publication in ApJ. Error bars in
Table 2 correcte