We present detailed fits of the spectral energy distributions (SEDs) of four submillimeter galaxies selected by the presence of a gamma-ray burst (GRB) event (GRBs 980703, 000210, 000418, and ...010222). These faint similar to 3 mJy submillimeter emitters at redshift similar to 1 are characterized by an unusual combination of long- and short-wavelength properties, namely enhanced submillimeter and/or radio emission combined with optical faintness and blue colors. We exclude an active galactic nucleus as the source of long-wavelength emission. From the SED fits, we conclude that the four galaxies are young (ages <2 Gyr), highly star forming (star formation rates similar to 150 M unk yr super(-1)), low mass (stellar masses similar to 10 super(10) M unk), and dusty (dust masses similar to 3 x 10 super(8) M unk). Their high dust temperatures (T sub(d) unk 45 K) indicate that GRB host galaxies are hotter, younger, and less massive counterparts to the submillimeter-selected galaxies detected so far. Future facilities like Herschel, the James Clerk Maxwell Telescope SCUBA-2, and ALMA will test this hypothesis, enabling measurement of dust temperatures of fainter GRB-selected galaxies.
We present detections at 850 ...m of the Lyman-break galaxy (LBG) population at z ... 3, 4, and 5 using data from the Submillimetre Common User Bolometer Array 2 Cosmology Legacy Survey in the United ...Kingdom Infrared Deep Sky Survey 'Ultra Deep Survey' field. We employ stacking to probe beneath the survey limit, measuring the average 850 ...m flux density of LBGs at z ... 3, 4, and 5 with typical ultraviolet luminosities of ... We measure 850 ...m flux densities of (0.25 ± 0.03), (0.41 ± 0.06), and (0.88 ± 0.23) mJy, respectively, finding that they contribute at most 20 per cent to the cosmic far-infrared (IR) background at 850 ...m. Fitting an appropriate range of spectral energy distributions to the z ~ 3, 4, and 5 LBG stacked 24-850 ...m fluxes, we derive IR luminosities of ... and star formation rates (SFRs) of ..., respectively. We find that the evolution in the IR luminosity density of LBGs is broadly consistent with model predictions for the expected contribution of luminous-to-ultraluminous IR galaxies at these epochs. We observe a positive correlation between stellar mass and IR luminosity and confirm that, for a fixed mass, the reddest LBGs (UV slope β ... 0) are redder due to dust extinction, with SFR(IR)/SFR(UV) increasing by about an order of magnitude over -2 < β < 0 with SFR(IR)/SFR(UV) ~ 20 for the reddest LBGs. Furthermore, the most massive LBGs tend to have higher obscured-to-unobscured ratios, hinting at a variation in the obscuration properties across the mass range. (ProQuest: ... denotes formulae/symbols omitted.)
ABSTRACT We introduce a new color selection technique to identify high-redshift, massive galaxies that are systematically missed by Lyman-break selection. The new selection is based on the H160 (H) ...and Infrared Array Camera (IRAC) 4.5 m bands, specifically mag. These galaxies, called "HIEROs," include two major populations that can be separated with an additional J − H color. The populations are massive and dusty star-forming galaxies at ( ) and extremely dusty galaxies at ( ). The 350 arcmin2 of the GOODS-North and GOODS-South fields with the deepest Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared and IRAC data contain as many as 285 HIEROs down to mag. Inclusion of the most extreme HIEROs, not even detected in the H band, makes this selection particularly complete for the identification of massive high-redshift galaxies. We focus here primarily on ( ) HIEROs, which have a median photometric redshift and stellar mass and are much fainter in the rest-frame UV than similarly massive Lyman-break galaxies (LBGs). Their star formation rates (SFRs), derived from their stacked infrared spectral energy distributions (SEDs), reach ∼240 yr−1, leading to a specific SFR, Gyr−1, suggesting that the sSFRs for massive galaxies continue to grow at but at a lower growth rate than from z = 0 to z = 2. With a median half-light radius of 2 kpc, including as compact as quiescent (QS) galaxies at similar redshifts, HIEROs represent perfect star-forming progenitors of the most massive ( ) compact QS galaxies at and have the right number density. HIEROs make up of all galaxies with identified at from their photometric redshifts. This is five times more than LBGs with nearly no overlap between the two populations. While HIEROs make up 15%-25% of the total SFR density at -5, they completely dominate the SFR density taking place in galaxies, and HIEROs are therefore crucial to understanding the very early phase of massive galaxy formation.
ABSTRACT
We present two new radio continuum images from the Australian Square Kilometre Array Pathfinder (ASKAP) survey in the direction of the Small Magellanic Cloud (SMC). These images are part of ...the Evolutionary Map of the Universe (EMU) Early Science Project (ESP) survey of the Small and Large Magellanic Clouds. The two new source lists produced from these images contain radio continuum sources observed at 960 MHz (4489 sources) and 1320 MHz (5954 sources) with a bandwidth of 192 MHz and beam sizes of 30.0 × 30.0 arcsec2 and 16.3 × 15.1 arcsec2, respectively. The median root mean square (RMS) noise values are 186 $\mu$Jy beam−1 (960 MHz) and 165 $\mu$Jy beam−1 (1320 MHz). To create point source catalogues, we use these two source lists, together with the previously published Molonglo Observatory Synthesis Telescope (MOST) and the Australia Telescope Compact Array (ATCA) point source catalogues to estimate spectral indices for the whole population of radio point sources found in the survey region. Combining our ASKAP catalogues with these radio continuum surveys, we found 7736 point-like sources in common over an area of 30 deg2. In addition, we report the detection of two new, low surface brightness supernova remnant candidates in the SMC. The high sensitivity of the new ASKAP ESP survey also enabled us to detect the bright end of the SMC planetary nebula sample, with 22 out of 102 optically known planetary nebulae showing point-like radio continuum emission. Lastly, we present several morphologically interesting background radio galaxies.
We present a meta-analysis of star formation rate (SFR) indicators in the Galaxy And Mass Assembly (GAMA) survey, producing 12 different SFR metrics and determining the SFR-M... relation for each. We ...compare and contrast published methods to extract the SFR from each indicator, using a well-defined local sample of morphologically selected spiral galaxies, which excludes sources which potentially have large recent changes to their SFR. The different methods are found to yield SFR-M... relations with inconsistent slopes and normalizations, suggesting differences between calibration methods. The recovered SFR-M... relations also have a large range in scatter which, as SFRs of the targets may be considered constant over the different time-scales, suggests differences in the accuracy by which methods correct for attenuation in individual targets. We then recalibrate all SFR indicators to provide new, robust and consistent luminosity-to-SFR calibrations, finding that the most consistent slopes and normalizations of the SFR-M... relations are obtained when recalibrated using the radiation transfer method of Popescu et al. These new calibrations can be used to directly compare SFRs across different observations, epochs and galaxy populations. We then apply our calibrations to the GAMA II equatorial data set and explore the evolution of star formation in the local Universe. We determine the evolution of the normalization to the SFR-M... relation from 0 < z < 0.35 -- finding consistent trends with previous estimates at 0.3 < z < 1.2. We then provide the definitive z < 0.35 cosmic star formation history, SFR-M... relation and its evolution over the last 3 billion years. (ProQuest: ... denotes formulae/symbols omitted.)
ABSTRACT
We present new Atacama Large Millimeter/Submillimeter Array (ALMA) 850
μ
m continuum observations of the original Ly
α
Blob (LAB) in the SSA22 field at
z
= 3.1 (SSA22-LAB01). The ALMA map ...resolves the previously identified submillimeter source into three components with a total flux density of
S
850
= 1.68 ± 0.06 mJy, corresponding to a star-formation rate of ∼150
M
⊙
yr
−1
. The submillimeter sources are associated with several faint (
m
≈ 27 mag) rest-frame ultraviolet sources identified in
Hubble Space Telescope
Imaging Spectrograph (STIS) clear filter imaging (
λ
≈ 5850 Å). One of these companions is spectroscopically confirmed with the Keck Multi-Object Spectrometer For Infra-Red Exploration to lie within 20 projected kpc and 250 km s
−1
of one of the ALMA components. We postulate that some of these STIS sources represent a population of low-mass star-forming satellites surrounding the central submillimeter sources, potentially contributing to their growth and activity through accretion. Using a high-resolution cosmological zoom simulation of a 10
13
M
⊙
halo at
z
= 3, including stellar, dust, and Ly
α
radiative transfer, we can model the ALMA+STIS observations and demonstrate that Ly
α
photons escaping from the central submillimeter sources are expected to resonantly scatter in neutral hydrogen, the majority of which is predicted to be associated with halo substructure. We show how this process gives rise to extended Ly
α
emission with similar surface brightness and morphology to observed giant LABs.
Aims. We investigate whether stellar dust sources i.e. asymptotic giant branch (AGB) stars and supernovae (SNe) can account for dust detected in 5 < z < 6.5 quasars (QSOs). Methods. We calculate the ...required dust yields per AGB star and per SN using the dust masses of QSOs inferred from their millimeter emission and stellar masses approximated as the difference between the dynamical and the H2 gas masses of these objects. Results. We find that AGB stars are not efficient enough to form dust in the majority of the z > 5 QSOs, whereas SNe may be able to account for dust in some QSOs. However, they require very high dust yields even for a top-heavy initial mass function. Conclusions. This suggests additional non-stellar dust formation mechanism e.g. significant dust grain growth in the interstellar medium of at least three out of nine z > 5 QSOs. SNe (but not AGB stars) may deliver enough heavy elements to fuel this growth.
Abstract
The mechanism by which galaxies stop forming stars and get rid of their interstellar medium (ISM) remains elusive. Here, we study a sample of more than 2000 elliptical galaxies in which dust ...emission has been detected. This is the largest sample of such galaxies ever analyzed. We infer the timescale for removal of dust in these galaxies and investigate its dependence on physical and environmental properties. We obtain a dust-removal timescale in elliptical galaxies of
τ
= 2.26 ± 0.18 Gyr, corresponding to a half-life time of 1.57 ± 0.12 Gyr. This timescale does not depend on environment, stellar mass, or redshift. We observe a departure of dusty elliptical galaxies from the relation between star formation rate and dust mass. This is caused by the star formation rates declining faster than the dust masses and indicates that there exists an internal mechanism that affects star formation but leaves the ISM intact. Morphological quenching together with ionization or outflows caused by older stellar populations (Type Ia supernovae or planetary nebulae) is consistent with these observations.
Ultra-faint galaxies are hosted by small dark matter halos with shallow gravitational potential wells, hence their star formation activity is more sensitive to feedback effects. The shape of the ...faint end of the high-z galaxy luminosity function (LF) contains important information on star formation and its interaction with the reionization process during the Epoch of Reionization. High-z galaxies with have only recently become accessible thanks to the Frontier Fields (FFs) survey combining deep HST imaging and the gravitational lensing effect. In this paper we investigate the faint end of the LF at redshift >5 using the data of FFs clusters Abell 2744 (A2744), MACSJ0416.1-2403 (M0416), MACSJ0717.5+3745 (M0717), and MACSJ1149.5+2223 (M1149). We analyze both an empirical and a physically motivated LF model to obtain constraints on a possible turnover of LF at faint magnitudes. In the empirical model the LF drops fast when the absolute UV magnitude is much larger than a turnover absolute UV magnitude . We obtain (15.2) at the 1 (2) confidence level (C.L.) for z ∼ 6. In the physically motivated analytical model, star formation in halos with circular velocity below is fully quenched if these halos are located in ionized regions. Using updated lensing models and new additional FFs data, we re-analyze previous constraints on and fesc presented by Castellano et al. using a smaller data set. We obtain new constraints on km s−1 and fesc 56% (both at 2 C.L.) and conclude that there is no turnover detected so far from the analyzed FFs data. Forthcoming JWST observations will be key to tightening these constraints further.
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