179 research outputs found
Detection of an ionized gas outflow in the extreme UV-luminous star-forming galaxy BOSS-EUVLG1 at z=2.47
BOSS-EUVLG1 is the most ultraviolet (UV) and Ly luminous galaxy
detected so far in the Universe, going through a very active starburst phase,
and forming stars at a rate (SFR) of 955 118 M yr. We
report the detection of a broad H component carrying 25% of the total
H flux. The broad H line traces a fast and massive ionized gas
outflow characterized by a total mass, of 7.94
0.15, an outflowing velocity (V) of 573 151 km s,
and an outflowing mass rate () of 44 20 M
yr. The presence of the outflow in BOSS-EUVLG1 is also supported by the
identification of blueshifted UV absorption lines in low and high ionization
states. The energy involved in the H outflow can be explained by the
ongoing star formation without the need for an Active Galactic Nucleus. The
derived low mass loading factor (= 0.05 0.03) indicates that
although massive, this phase of the outflow can not be relevant for the
quenching of the star formation. In addition, only a small fraction (
15%) of the ionized outflowing material with velocities above 372 km s
could escape the gravitational potential, and enrich the surrounding
circum-galactic medium at distances above tens of kpc. The ionized phase of the
outflow does not carry the mass and energy to play a relevant role neither in
the evolution of the host galaxy nor in the enrichment of the intergalactic
medium. Other phases of the outflow could be carrying most of the outflow
energy and mass in the form of hot X-ray emitting gas as predicted by some
recent simulations. The expected emission of the extended X-ray emitting halo
associated with the outflow in BOSS-EUVLG1 and similar galaxies could be
detected with the future X-ray observatory, {\it ATHENA} but could not be
resolved spatially.Comment: 8 pages, 3 figures, accepted in A&
On the Multiplicity of ALMA Compact Array counterparts of far-infrared bright quasars
We present ALMA Atacama Compact Array (ACA) 870 ÎŒm continuum maps of 28 infrared-bright SDSS quasars with Herschel/SPIRE detections at redshifts 2-4, the largest such sample ever observed with ALMA. The ACA detections are centred on the SDSS coordinates to within 1 âł for about 80 per cent of the sample. Larger offsets indicate that the far-infrared (FIR) emission detected by Herschel might come from a companion source. The majority of the objects (Âż70 per cent) have unique ACA counterparts within the SPIRE beam down to 3âł-4âł resolution. Only 30 per cent of the sample shows clear evidence for multiple sources with secondary counterparts contributing to the total 870 ÎŒm flux within the SPIRE beam to at least 25 per cent. We discuss the limitations of the data based on simulated pairs of point-like sources at the resolution of the ACA and present an extensive comparison of our findings with recent works on the multiplicities of sub-millimetre galaxies. We conclude that, despite the coarse resolution of the ACA, our data support the idea that, for a large fraction of FIR-bright quasars, the sub-mm emission comes from single sources. Our results suggest that, on average, optically bright quasars with strong FIR emission are not triggered by early-stage mergers but are, instead, together with their associated star formation rates, the outcome of either late-stage mergers or secular processes
Young Galaxy Candidates in the Hubble Frontier Fields - III. MACSJ0717.5+3745
In this paper we present the results of our search for and study of galaxy candidates behind the third Frontier Fields (FF) cluster,
MACSJ0717.5+3745, and its parallel field, combining data from Hubble and
Spitzer. We select 39 candidates using the Lyman Break technique, for which the
clear non-detection in optical make the extreme mid- interlopers hypothesis
unlikely. We also take benefit from samples selected using
previous Frontier Fields datasets of Abell 2744 and MACS0416 to improve the
constraints on the properties of very high-redshift objects. We compute the
redshift and the physical properties, such emission lines properties, star
formation rate, reddening, and stellar mass for all Frontier Fields objects
from their spectral energy distribution using templates including nebular
emission lines. We study the relationship between several physical properties
and confirm the trend already observed in previous surveys for evolution of
star formation rate with galaxy mass, and between the size and the UV
luminosity of our candidates. The analysis of the evolution of the UV
Luminosity Function with redshift seems more compatible with an evolution of
density. Moreover, no robust 8.5 object is selected behind the cluster
field, and few 9 candidates have been selected in the two previous
datasets from this legacy survey, suggesting a strong evolution in the number
density of galaxies between 8 and 9. Thanks to the use of the lensing
cluster, we study the evolution of the star formation rate density produced by
galaxies with L0.03L, and confirm the strong decrease observed
between 8 and 9.Comment: 21 pages - Accepted for publication in ApJ - v2: small correction
Optical polarization and spectral properties of the H-poor superluminous supernovae SN 2021bnw and SN 2021fpl
New optical photometric, spectrocopic and imaging polarimetry data are
combined with publicly available data to study some of the physical properties
of the two H-poor superluminous supernovae (SLSN) SN 2021bnw and SN 2021fpl.
For each SLSN, the best-fit parameters obtained from the magnetar model with
\texttt{MOSFiT} do not depart from the range of parameter obtained on other
SLSNe discussed in the literature. A spectral analysis with \texttt{SYN++}
shows that SN 2021bnw is a W Type, Fast evolver, while SN 2021fpl is a 15bn
Type, Slow evolver. The analysis of the polarimetry data obtained on SN 2021fpl
at four epochs (+1.8, +20.6, +34.1 and +43.0 days, rest-frame) shows polarization detections in the range 0.8--1 . A comparison of the
spectroscopy data suggests that SN 2021fpl underwent a spectral transition a
bit earlier than SN 2015bn, during which, similarly, it could have underwent a
polarization transition. The analysis of the polarimetry data obtained on SN
2021bnw do not show any departure from symmetry of the photosphere at an
empirical diffusion timescale of 2 (+81.1 days rest-frame). This
result is consistent with those on the sample of W Type SLSN observed at
empirical diffusion timescale 1 with that technique, even though it is
not clear the effect of limited spectral windows varying from one object to the
other. Measurements at higher empirical diffusion timescale may be needed to
see any departure from symmetry as it is discussed in the literature for SN
2017egm.Comment: 29 pages, 13 Figures, 15 Tables, submitted to the MNRA
The nature of 500 micron risers I: SMA observations
We present SMA observations at resolutions from 0.35 to 3âarcsec of a sample of 34 candidate high redshift dusty star forming galaxies (DSFGs). These sources were selected from the HerMES Herschel survey catalogues to have SEDs rising from 250 to 350 to 500âÎŒm, a population termed 500-risers. We detect counterparts to 24 of these sources, with four having two counterparts. We conclude that the remaining ten sources that lack detected counterparts are likely to have three or more associated sources which blend together to produce the observed Herschel source. We examine the role of lensing, which is predicted to dominate the brightest (F500 > 60âmJy) half of our sample. We find that while lensing plays a role, at least 35 perâcent of the bright sources are likely to be multiple sources rather than the result of lensing. At fainter fluxes we find a blending rate comparable to, or greater than, the predicted 40 perâcent. We determine far-IR luminosities and star formation rates for the non-multiple sources in our sample and conclude that, in the absence of strong lensing, our 500-risers are very luminous systems with LFIR > 1013âLâ and star formation rates >1000âMââyrâ1
Frontier Fields : Combining HST, VLT and Spitzer data to explore the 8 Universe behind the lensing cluster MACS04162403
(Abridged) The HST Frontier Fields project started at the end of 2013 with
the aim of providing extremely deep images of 6 massive galaxy clusters. One of
the main goals of this program is to push several telescopes to their limits in
order to provide the best current view of the earliest stages of the Universe.
We present a detailed analysis of 8 objects behind the HFFs lensing
cluster, MACS0416-2403, combining 0.3-1.6 m imaging from HST, ground-based
imaging from VLT HAWK-I, and 3.6 m and 4.5 m Spitzer Space
Telescope. We apply the classical Lyman Break technique, combining
non-detection criteria and color-selection. In order to avoid contamination by
mid- interlopers, we require a strong break between optical and near
infrared data. The luminosity function at 8 is computed using a MC
method taking advantage of the SED-fitting results. A piece of cautionary
information is gleaned from new deep optical photometry of a previously
identified 8 galaxy in this cluster, which is now firmly detected as a
mid- interloper with a strong mag Balmer break (between F606W
and F125W). Using the SED of this interloper, we estimate the contamination
rate of our MACS04162403 sample, as well as for previous samples in Abell
2744 based on HFF data. Our selection recovers 4 robust objects with
m ranging from 26.0 to 27.9 AB and located in modest amplification
regions (2.4). Two of the objects display a secondary break between the
IRAC 3.6 m and 4.5 m bands which could be associated to the Balmer
break or emission lines at 8. The candidates generally have star
formation rates around 10 M/yr and sizes ranging from 0.2 to
0.5 kpc, in good agreement with previous observations and expectations for
objects in the early Universe.Comment: 11 pages, 8 figures, accepted for publication in A&
HerMES: A Statistical Measurement of the Redshift Distribution of Herschel-SPIRE Sources Using the Cross-correlation Technique
The wide-area imaging surveys with the Herschel Space Observatory at submillimeter (sub-mm) wavelengths have now resulted in catalogs of the order of one-hundred-thousand dusty, starburst galaxies. These galaxies capture an important phase of galaxy formation and evolution, but, unfortunately, the redshift distribution of these galaxies, N(z), is still mostly uncertain due to limitations associated with counterpart identification at optical wavelengths and spectroscopic follow-up. We make a statistical estimate of N(z) using a clustering analysis of sub-mm galaxies detected at each of 250, 350 and 500 ÎŒm from the Herschel Multi-tiered Extragalactic Survey centered on the Boötes field. We cross-correlate Herschel galaxies against galaxy samples at optical and near-IR wavelengths from the Sloan Digital Sky Survey, the NOAO Deep Wide Field Survey, and the Spitzer Deep Wide Field Survey. We create optical and near-IR galaxy samples based on their photometric or spectroscopic redshift distributions and test the accuracy of those redshift distributions with similar galaxy samples defined with catalogs from the Cosmological Evolution Survey (COSMOS), which has superior spectroscopic coverage. We model the clustering auto- and cross-correlations of Herschel and optical/IR galaxy samples to estimate N(z) and clustering bias factors. The S_(350) > 20 mJy galaxies have a bias factor varying with redshift as b(z) = 1.0^(+1.0)_(â0.5)(1 + z)^1.2^(+0.3)_(â0.7). This bias and the redshift dependence is broadly in agreement with galaxies that occupy dark matter halos of mass in the range of 1012 to 10^(13) M_â. We find that galaxy selections in all three Spectral and Photometric Imaging Receiver (SPIRE) bands share a similar average redshift, with = 1.8 ± 0.2 for 250 ÎŒm selected samples, and = 1.9 ± 0.2 for both 350 and 500 ÎŒm samples, while their distributions behave differently. For 250 ÎŒm selected galaxies we find the a larger number of sources with z †1 when compared with the subsequent two SPIRE bands, with 350 and 500 ÎŒm selected SPIRE samples having peaks in N(z) at progressively higher redshifts. We compare our clustering-based N(z) results to sub-mm galaxy model predictions in the literature, and with an estimate of N(z) using a stacking analysis of COSMOS 24 ÎŒm detections
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A 15 ”m selected sample of hHigh-z starbursts and AGNs
We report results from our Spitzer GO-1 program on IRS spectroscopy of a large sample of Luminous Infrared Galaxies and quasars selected from the European Large Area ISO Survey (ELAIS). The selected ELAIS sources have a wide multi-wavelength coverage, including ISOCAM, ISOPHOT, IRAC
and MIPS (from SWIRE), and optical photometry. Here we present the sample selection and results from the IRS spectroscopy
Evidence for very massive stars in extremely UV-bright star-forming galaxies at z ⌠2.2 â 3.6
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