23 research outputs found
The Extremely Luminous Quasar Survey in the Pan-STARRS 1 Footprint (PS-ELQS)
We present the results of the Extremely Luminous Quasar Survey in the
survey of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS;
PS1). This effort applies the successful quasar selection strategy of the
Extremely Luminous Survey in the Sloan Digital Sky Survey footprint
() to a much larger area
(). This spectroscopic survey targets the most
luminous quasars (; ) at intermediate redshifts
(). Candidates are selected based on a near-infrared JKW2 color cut
using WISE AllWISE and 2MASS photometry to mainly reject stellar contaminants.
Photometric redshifts () and star-quasar classifications for each
candidate are calculated from near-infrared and optical photometry using the
supervised machine learning technique random forests. We select 806 quasar
candidates at from a parent sample of 74318 sources. After
exclusion of known sources and rejection of candidates with unreliable
photometry, we have taken optical identification spectra for 290 of our 334
good PS-ELQS candidates. We report the discovery of 190 new quasars
and an additional 28 quasars at lower redshifts. A total of 44 good PS-ELQS
candidates remain unobserved. Including all known quasars at , our
quasar selection method has a selection efficiency of at least . At lower
declinations we approximately triple the known
population of extremely luminous quasars. We provide the PS-ELQS quasar catalog
with a total of 592 luminous quasars (, ). This unique
sample will not only be able to provide constraints on the volume density and
quasar clustering of extremely luminous quasars, but also offers valuable
targets for studies of the intergalactic medium.Comment: 34 pages, 10 figures, accepted to ApJ
ALMA Observations of the Sub-kpc Structure of the Host Galaxy of a z= 6.5 Lensed Quasar: A Rotationally-Supported Hyper-Starburst System at the Epoch of Reionization
We report ALMA observations of the dust continuum and {\cii} emission of the
host galaxy of J0439+1634, a gravitationally lensed quasar at .
Gravitational lensing boosts the source-plane resolution to \sim0\farcs15
. The lensing model derived from the ALMA data is
consistent with the fiducial model in \citet{fan19} based on {\it HST} imaging.
The host galaxy of J0439+1634 can be well-fitted by a S\'ersic profile
consistent with an exponential disk, both in the far-infrared (FIR) continuum
and the {\cii} emission. The overall magnification is for the
continuum and for the {\cii} line. The host galaxy of J0439+1634
is a compact ultra-luminous infrared galaxy, with a total star formation rate
(SFR) of after correcting for lensing and
an effective radius of kpc. The resolved regions in J0439+1634 follow
the ``{\cii} deficit," where the {\cii}-to-FIR ratio decreases with FIR surface
brightness. The reconstructed velocity field of J0439+1634 appears to be
rotation-like. The maximum line-of-sight rotation velocity of 130 km/s at a
radius of 2 kpc. However, our data cannot be fit by an axisymmetric thin
rotating disk, and the inclination of the rotation axis, , remains
unconstrained. We estimate the dynamical mass of the host galaxy to be
. J0439+1634 is likely to have a high
gas-mass fraction and an oversized SMBH compared to local relations. The SFR of
J0439+1634 reaches the maximum possible values, and the SFR surface density is
close to the highest value seen in any star-forming galaxy currently known in
the universe.Comment: 14 pages, 7 figures. Accepted by Ap
Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies II. Momentum-Driven Winds Powered by Star Formation in the Early Universe
Galactic outflows of molecular gas are a common occurrence in galaxies and
may represent a mechanism by which galaxies self-regulate their growth,
redistributing gas that could otherwise have formed stars. We previously
presented the first survey of molecular outflows at z > 4 towards a sample of
massive, dusty galaxies. Here we characterize the physical properties of the
molecular outflows discovered in our survey. Using low-redshift outflows as a
training set, we find agreement at the factor-of-two level between several
outflow rate estimates. We find molecular outflow rates 150-800Msun/yr and
infer mass loading factors just below unity. Among the high-redshift sources,
the molecular mass loading factor shows no strong correlations with any other
measured quantity. The outflow energetics are consistent with expectations for
momentum-driven winds with star formation as the driving source, with no need
for energy-conserving phases. There is no evidence for AGN activity in our
sample, and while we cannot rule out deeply-buried AGN, their presence is not
required to explain the outflow energetics, in contrast to nearby obscured
galaxies with fast outflows. The fraction of the outflowing gas that will
escape into the circumgalactic medium (CGM), though highly uncertain, may be as
high as 50%. This nevertheless constitutes only a small fraction of the total
cool CGM mass based on a comparison to z~2-3 quasar absorption line studies,
but could represent >~10% of the CGM metal mass. Our survey offers the first
statistical characterization of molecular outflow properties in the very early
universe.Comment: ApJ accepted. 25 pages, 16 figures. Data and tables from Papers I and
II available at https://github.com/spt-smg/publicdat
Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies I. Sample Overview and Clumpy Structure in Molecular Outflows on 500pc Scales
Massive galaxy-scale outflows of gas are one of the most commonly-invoked
mechanisms to regulate the growth and evolution of galaxies throughout the
universe. While the gas in outflows spans a large range of temperatures and
densities, the cold molecular phase is of particular interest because molecular
outflows may be capable of suppressing star formation in galaxies by removing
the star-forming gas. We have conducted the first survey of molecular outflows
at z > 4, targeting 11 strongly-lensed dusty, star-forming galaxies (DSFGs)
with high-resolution Atacama Large Millimeter Array (ALMA) observations of OH
119um absorption as an outflow tracer. In this first paper, we give an overview
of the survey, focusing on the detection rate and structure of molecular
outflows. We find unambiguous evidence for outflows in 8/11 (73%) galaxies,
more than tripling the number known at z > 4. This implies that molecular winds
in z > 4 DSFGs must have both a near-unity occurrence rate and large opening
angles to be detectable in absorption. Lensing reconstructions reveal that
500pc-scale clumpy structures in the outflows are common. The individual clumps
are not directly resolved, but from optical depth arguments we expect that
future observations will require 50-200pc spatial resolution to do so. We do
not detect high-velocity [CII] wings in any of the sources with clear OH
outflows, indicating that [CII] is not a reliable tracer of molecular outflows.
Our results represent a first step toward characterizing molecular outflows at
z > 4 at the population level, demonstrating that large-scale outflows are
ubiquitous among early massive, dusty galaxies.Comment: ApJ accepted. 28 pages, 12 figures + appendix. Data and tables from
Papers I and II available at https://github.com/spt-smg/publicdat
Chaotic and Clumpy Galaxy Formation in an Extremely Massive Reionization-era Halo
© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. https://creativecommons.org/licenses/by/4.0/Abstract: The SPT 0311–58 system at z = 6.900 is an extremely massive structure within the reionization epoch and offers a chance to understand the formation of galaxies at an extreme peak in the primordial density field. We present 70 mas Atacama Large Millimeter/submillimeter Array observations of the dust continuum and [C ii] 158 μm emission in the central pair of galaxies and reach physical resolutions of ∼100–350 pc, among the most detailed views of any reionization-era system to date. The observations resolve the source into at least a dozen kiloparsec-size clumps. The global kinematics and high turbulent velocity dispersion within the galaxies present a striking contrast to recent claims of dynamically cold thin-disk kinematics in some dusty galaxies just 800 Myr later at z ∼ 4. We speculate that both gravitational interactions and fragmentation from massive parent disks have likely played a role in the overall dynamics and formation of clumps in the system. Each clump individually is comparable in mass to other 6 < z < 8 galaxies identified in rest-UV/optical deep field surveys, but with star formation rates elevated by a factor of ~3-5. Internally, the clumps themselves bear close resemblance to greatly scaled-up versions of virialized cloud-scale structures identified in low-redshift galaxies. Our observations are qualitatively similar to the chaotic and clumpy assembly within massive halos seen in simulations of high-redshift galaxies.Peer reviewe
Nature of the Diffuse Source and Its Central Point-like Source in SNR 0509–67.5
We examine a diffuse emission region near the center of SNR 0509-67.5 to determine its nature. Within this diffuse region we observe a point-like source that is bright in the near-IR, but is not visible in the B and V bands. We consider an emission line observed at 6766 angstrom and the possibilities that it is Ly alpha, H alpha, and [O II] lambda 3727. We examine the spectral energy distribution (SED) of the source, comprised of Hubble Space Telescope B, V, I, J, and H bands in addition to Spitzer/IRAC 3.6, 4.5, 5.8, and 8 mu m bands. The peak of the SED is consistent with a background galaxy at z approximate to 0.8 +/- 0.2 and a possible Balmer jump places the galaxy at z approximate to 0.9 +/- 0.3. These SED considerations support the emission line's identification as [O II] lambda 3727. We conclude that the diffuse source in SNR 0509-67.5 is a background galaxy at z approximate to 0.82. Furthermore, we identify the point-like source superposed near the center of the galaxy as its central bulge. Finally, we find no evidence for a surviving companion star, indicating a double-degenerate origin for SNR 0509-67.5.NASA [HST-GO13282.01-A]; U.S. National Science Foundation [AST-1312950]; Taiwanese Ministry of Science and Technology [MOST 104-2112-M-001044-MY3]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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Nature of the Diffuse Source and Its Central Point-like Source in SNR 0509-67.5
We examine a diffuse emission region near the center of SNR 0509-67.5 to determine its nature. Within this diffuse region we observe a point-like source that is bright in the near-IR, but is not visible in the B and V bands. We consider an emission line observed at 6766 angstrom and the possibilities that it is Ly alpha, H alpha, and [O II] lambda 3727. We examine the spectral energy distribution (SED) of the source, comprised of Hubble Space Telescope B, V, I, J, and H bands in addition to Spitzer/IRAC 3.6, 4.5, 5.8, and 8 mu m bands. The peak of the SED is consistent with a background galaxy at z approximate to 0.8 +/- 0.2 and a possible Balmer jump places the galaxy at z approximate to 0.9 +/- 0.3. These SED considerations support the emission line's identification as [O II] lambda 3727. We conclude that the diffuse source in SNR 0509-67.5 is a background galaxy at z approximate to 0.82. Furthermore, we identify the point-like source superposed near the center of the galaxy as its central bulge. Finally, we find no evidence for a surviving companion star, indicating a double-degenerate origin for SNR 0509-67.5.NASA [HST-GO13282.01-A]; U.S. National Science Foundation [AST-1312950]; Taiwanese Ministry of Science and Technology [MOST 104-2112-M-001044-MY3]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Spatially Resolved [C ii] Emission in SPT0346-52: A Hyper-starburst Galaxy Merger at z ∼ 5.7
International audienceSPT0346-52 is one of the most most luminous and intensely star-forming galaxies in the universe, with {L}FIR}> {10}13 {\text{}}{L}ȯ and {{{Σ }}}SFR}≈ 4200 {\text{}}{M}ȯ {yr}}-1 {kpc}}-2. In this paper, we present ∼ 0\buildrel{\prime\prime}\over{.} 15 ALMA observations of the [{{C}} {{II}}] 158 μm emission line in this z = 5.7 dusty star-forming galaxy. We use a pixellated lensing reconstruction code to spatially and kinematically resolve the source-plane [{{C}} {{II}}] and rest-frame 158 μm dust continuum structure at ∼700 pc (∼0.″12) resolution. We discuss the [{{C}} {{II}}] deficit with a pixellated study of the L [C II]/L FIR ratio in the source plane. We find that individual pixels within the galaxy follow the same trend found using unresolved observations of other galaxies, indicating that the deficit arises on scales ≲700 pc. The lensing reconstruction reveals two spatially and kinematically separated components (∼1 kpc and ∼500 km s‑1 apart) connected by a bridge of gas. Both components are found to be globally unstable, with Toomre Q instability parameters \ll 1 everywhere. We argue that SPT0346-52 is undergoing a major merger, which is likely driving the intense and compact star formation
Multiphase ISM in the z = 5.7 Hyperluminous Starburst SPT 0346-52
International audienceWith ΣSFR ~ 4200 M ⊙ yr-1 kpc-2, SPT 0346-52 (z = 5.7) is the most intensely star-forming galaxy discovered by the South Pole Telescope. In this paper, we expand on previous spatially resolved studies, using ALMA observations of dust continuum, [N II] 205 μm, [C II] 158 μm, [O I] 146 μm, and undetected [N II] 122 μm and [O I] 63 μm emission to study the multiphase interstellar medium (ISM) in SPT 0346-52. We use pixelated, visibility-based lens modeling to reconstruct the source-plane emission. We also model the source-plane emission using the photoionization code CLOUDY and find a supersolar metallicity system. We calculate T dust = 48.3 K and λ peak = 80 μm and see line deficits in all five lines. The ionized gas is less dense than comparable galaxies, with n e -3, while ~20% of the [C II] 158 μm emission originates from the ionized phase of the ISM. We also calculate the masses of several phases of the ISM. We find that molecular gas dominates the mass of the ISM in SPT 0346-52, with the molecular gas mass ~4× higher than the neutral atomic gas mass and ~100× higher than the ionized gas mass
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Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies. II. Momentum-driven Winds Powered by Star Formation in the Early Universe
Galactic outflows of molecular gas are a common occurrence in galaxies and
may represent a mechanism by which galaxies self-regulate their growth,
redistributing gas that could otherwise have formed stars. We previously
presented the first survey of molecular outflows at z > 4 towards a sample of
massive, dusty galaxies. Here we characterize the physical properties of the
molecular outflows discovered in our survey. Using low-redshift outflows as a
training set, we find agreement at the factor-of-two level between several
outflow rate estimates. We find molecular outflow rates 150-800Msun/yr and
infer mass loading factors just below unity. Among the high-redshift sources,
the molecular mass loading factor shows no strong correlations with any other
measured quantity. The outflow energetics are consistent with expectations for
momentum-driven winds with star formation as the driving source, with no need
for energy-conserving phases. There is no evidence for AGN activity in our
sample, and while we cannot rule out deeply-buried AGN, their presence is not
required to explain the outflow energetics, in contrast to nearby obscured
galaxies with fast outflows. The fraction of the outflowing gas that will
escape into the circumgalactic medium (CGM), though highly uncertain, may be as
high as 50%. This nevertheless constitutes only a small fraction of the total
cool CGM mass based on a comparison to z~2-3 quasar absorption line studies,
but could represent >~10% of the CGM metal mass. Our survey offers the first
statistical characterization of molecular outflow properties in the very early
universe