We present the first results from the deep and wide 5 GHz radio observations of the Great Observatories Origins Deep Survey (GOODS)-North ( = 3.5 Jy beam−1, synthesized beam size θ = 1 47 × 1 42, and ...52 sources over 109 arcmin2) and GOODS-South ( = 3.0 Jy beam−1, θ = 0 98 × 0 45, and 88 sources over 190 arcmin2) fields using the Karl G. Jansky Very Large Array. We derive radio spectral indices between 1.4 and 5 GHz using the beam-matched images and show that the overall spectral index distribution is broad even when the measured noise and flux bias are considered. We also find a clustering of faint radio sources around = 0.8, but only within S5 GHz < 150 Jy. We demonstrate that the correct radio spectral index is important for deriving accurate rest-frame radio power and analyzing the radio-FIR correlation, and adopting a single value of = 0.8 leads to a significant scatter and a strong bias in the analysis of the radio-FIR correlation, resulting from the broad and asymmetric spectral index distribution. When characterized by specific star formation rates, the starburst population (58%) dominates the 5 GHz radio source population, and the quiescent galaxy population (30%) follows a distinct trend in spectral index distribution and the radio-FIR correlation. Lastly, we offer suggestions on sensitivity and angular resolution for future ultra-deep surveys designed to trace the cosmic history of star formation and AGN activity using radio continuum as a probe.
Abstract
We present the 3 mm wavelength spectra of 28 local galaxy merger remnants obtained with the Large Millimeter Telescope. Sixteen molecular lines from 14 different molecular species and ...isotopologues were identified, and 21 out of 28 sources were detected in one or more molecular lines. On average, the line ratios of the dense gas tracers, such as HCN (1–0) and HCO
+
(1–0), to
13
CO (1–0) are 3–4 times higher in ultra/luminous infrared galaxies (U/LIRGs) than in non-LIRGs in our sample. These high line ratios could be explained by the deficiency of
13
CO and high dense gas fractions suggested by high HCN (1–0)/
12
CO (1–0) ratios. We calculate the IR-to-HCN (1–0) luminosity ratio as a proxy of the dense gas star formation efficiency. There is no correlation between the IR/HCN ratio and the IR luminosity, while the IR/HCN ratio varies from source to source ((1.1–6.5) × 10
3
L
☉
/(K km s
−1
pc
2
)). Compared with the control sample, we find that the average IR/HCN ratio of the merger remnants is higher by a factor of 2–3 than those of the early/mid-stage mergers and nonmerging LIRGs, and it is comparable to that of the late-stage mergers. The IR-to-
12
CO (1–0) ratios show a similar trend to the IR/HCN ratios. These results suggest that star formation efficiency is enhanced by the merging process and maintained at high levels even after the final coalescence. The dynamical interactions and mergers could change the star formation mode and continue to impact the star formation properties of the gas in the postmerger phase.
Abstract
Mechanisms regulating the escape of Ly
α
photons and ionizing radiation remain poorly understood. To study these processes, we analyze Very Large Array 21 cm observations of one Green Pea ...(GP), J160810+352809 (hereafter J1608), and
Hubble Space Telescope
Cosmic Origins Spectrograph (COS) spectra of 17 GP galaxies at
. All are highly ionized: J1608 has the highest O
iii
λ
5007/O
ii
λ
3727 for star-forming galaxies in Sloan Digital Sky Survey, and the 17 GPs have O
iii/O
ii
≥ 6.6. We set an upper limit on J1608's H
i
mass of
, near or below average compared to similar-mass dwarf galaxies. In the COS sample, eight GPs show Ly
α
absorption components, six of which also have Ly
α
emission. The H
i
column densities derived from Ly
α
absorption are high,
cm
−2
= 19–21, well above the LyC optically thick limit. Using low-ionization absorption lines, we measure covering fractions (
) of 0.1–1 and find that
strongly anticorrelates with Ly
α
escape fraction. Low covering fractions may facilitate Ly
α
and LyC escape through dense neutral regions. GPs with
all have low neutral gas velocities, while GPs with lower
have a larger range of velocities. Conventional mechanical feedback may help establish low
in some cases, whereas other processes may be important for GPs with low velocities. Finally, we compare
with proposed indicators of LyC escape. Ionizing photon escape likely depends on a combination of neutral gas geometry and kinematics, complicating the use of emission-line diagnostics for identifying LyC emitters.
Abstract
The PASSAGES (Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts) collaboration has recently defined a sample of 30 gravitationally lensed dusty star-forming galaxies ...(DSFGs). These rare, submillimeter-selected objects enable high-resolution views of the most extreme sites of star formation in galaxies at cosmic noon. Here, we present the first major compilation of strong lensing analyses using
lenstool
for PASSAGES, including 15 objects spanning
z
= 1.1–3.3, using complementary information from 0.″6-resolution 1.1 mm Atacama Large Millimeter/submillimeter Array and 0.″4 5 cm Jansky Very Large Array continuum imaging, in tandem with 1.6
μ
m Hubble and optical imaging with Gemini-S. Magnifications range from
μ
= 2 to 28 (median
μ
= 7), yielding intrinsic infrared luminosities of
L
IR
= 0.2–5.9 × 10
13
L
⊙
(median 1.4 × 10
13
L
⊙
) and inferred star formation rates of 170–6300
M
⊙
yr
−1
(median 1500
M
⊙
yr
−1
). These results suggest that the PASSAGES objects comprise some of the most extreme known starbursts, rivaling the luminosities of even the brightest unlensed objects, further amplified by lensing. The intrinsic sizes of far-infrared continuum regions are large (
R
e
= 1.7–4.3 kpc; median 3.0 kpc) but consistent with
L
IR
–
R
e
scaling relations for
z
> 1 DSFGs, suggesting a widespread spatial distribution of star formation. With modestly high angular resolution, we explore if these objects might be maximal starbursts. Instead of approaching Eddington-limited surface densities, above which radiation pressure will disrupt further star formation, they are safely sub-Eddington—at least on global, galaxy-integrated scales.
ABSTRACT The central structure in three of the brightest unlensed z = 3-4 submillimeter galaxies is investigated through 0 015-0 05 (120-360 pc) 860 m continuum images obtained using the Atacama ...Large Millimeter/submillimeter Array (ALMA). The distribution in the central kiloparsec in AzTEC1 and AzTEC8 is extremely complex, and they are composed of multiple ∼200 pc clumps. AzTEC4 consists of two sources that are separated by ∼1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ∼300-3000 M yr−1 kpc−2, suggesting regions with extreme star formation near the Eddington limit. By comparing the flux obtained by ALMA and Submillimeter Array, we find that 68%-90% of the emission is extended ( 1 kpc) in AzTEC4 and 8. For AzTEC1, we identify at least 11 additional compact (∼200 pc) clumps in the extended 3-4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at 150 pc scales are roughly similar to that observed in local ULIRGs, as in the eastern nucleus of Arp 220. Between 10% and 30% of the 860 m continuum is concentrated in clumpy structures in the central kiloparsec, while the remaining flux is distributed over 1 kpc regions, some of which could also be clumpy. These sources can be explained by a rapid inflow of gas such as a merger of gas-rich galaxies, surrounded by extended and clumpy starbursts. However, the cold mode accretion model is not ruled out.
Abstract
We report the detection of an ionized gas outflow from an X-ray active galactic nucleus hosted in a massive quiescent galaxy in a protocluster at
z
= 3.09 (J221737.29+001823.4). It is a ...type-2 QSO with broad (
W
80
> 1000 km s
−1
) and strong (
log
(
L
OIII
/erg s
−1
) ≈ 43.4) O
iii
λ
λ
4959,5007 emission lines detected by slit spectroscopy in three-position angles using Multi-Object Infra-Red Camera and Spectrograph (MOIRCS) on the Subaru telescope and the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) on the Keck-I telescope. In the all slit directions, O
iii
emission is extended to ∼15 physical kpc and indicates a powerful outflow spreading over the host galaxy. The inferred ionized gas mass outflow rate is 22 ± 3
M
⊙
yr
−1
. Although it is a radio source, according to the line diagnostics using H
β
, O
ii
, and O
iii
, photoionization by the central QSO is likely the dominant ionization mechanism rather than shocks caused by radio jets. On the other hand, the spectral energy distribution of the host galaxy is well characterized as a quiescent galaxy that has shut down star formation several hundred Myr ago. Our results suggest a scenario that QSOs are powered after the shutdown of the star formation and help complete the quenching of massive quiescent galaxies at high redshift.
We report 1.1-mm number counts revealed with the Atacama Large Millimeter/submillimeter Array (ALMA) in the Subaru/XMM-Newton Deep Survey Field (SXDF). The advent of ALMA enables us to reveal ...millimeter-wavelength number counts down to the faint end without source confusion. However, previous studies are based on the ensemble of serendipitously detected sources in fields originally targeting different sources and could be biased due to the clustering of sources around the targets. We derive number counts in the flux range of 0.2–2 mJy by using 23 (≥4σ) sources detected in a continuous 2.0-arcmin2 area of the SXDF. The number counts are consistent with previous results within errors, suggesting that the counts derived from serendipitously detected sources are not significantly biased, although there could be field-to-field variation due to the small survey area. By using the best-fitting function of the number counts, we find that ∼40% of the extragalactic background light at 1.1 mm is resolved at S
1.1mm > 0.2 mJy.
We present new Atacama Large Millimeter Array (ALMA) dust continuum observations of 101 galaxies in the COSMOS field to study the effect of the environment on the interstellar medium at z ∼ 0.7. At ...this redshift, our targets span a wide range of environments allowing for a diverse sample of galaxies with densities of = 0.16-10.5 Mpc−2 (per Δz = 0.024). Using the ALMA observations, we calculate the total interstellar medium (ISM) mass (MISM) and look for depletion as a function of galaxy density in order to understand the quenching or triggering of star formation in galaxies in different environments. MISM is found to have a small dependence on the environment, while the depletion timescale remains constant (∼200 Myr) across all environments. We find elevated MISM values at intermediate densities and lower values at high densities compared to low (field) densities. Our observed evolution in gas fraction with density in this single redshift slice is equivalent to the observed evolution with cosmic time over 2-3 Gyr. To explain the change in the gas mass fraction seen in galaxies in intermediate and high densities, these results suggest environmental processes such as mergers and ram pressure stripping are likely playing a role in dense filamentary cluster environments.
Abstract
Gradients in the mass-to-light ratio of distant galaxies impede our ability to characterize their size and compactness. The long-wavelength filters of JWST’s NIRCam offer a significant step ...forward. For galaxies at Cosmic Noon (
z
∼ 2), this regime corresponds to the rest-frame near-infrared, which is less biased toward young stars and captures emission from the bulk of a galaxy’s stellar population. We present an initial analysis of an extraordinary lensed dusty star-forming galaxy at
z
= 2.3 behind the El Gordo cluster (
z
= 0.87), named El Anzuelo (“The Fishhook”) after its partial Einstein-ring morphology. The far-UV to near-IR spectral energy distribution suggests an intrinsic star formation rate of
81
−
2
+
7
M
⊙
yr
−
1
and dust attenuation
A
V
≈ 1.6, in line with other DSFGs on the star-forming main sequence. We develop a parametric lens model to reconstruct the source-plane structure of dust imaged by the Atacama Large Millimeter/submillimeter Array, far-UV to optical light from Hubble, and near-IR imaging with 8 filters of JWST/NIRCam, as part of the Prime Extragalactic Areas for Reionization and Lensing Science program. The source-plane half-light radius is remarkably consistent from ∼1 to 4.5
μ
m, despite a clear color gradient where the inferred galaxy center is redder than the outskirts. We interpret this to be the result of both a radially decreasing gradient in attenuation and substantial spatial offsets between UV- and IR-emitting components. A spatial decomposition of the SED reveals modestly suppressed star formation in the inner kiloparsec, which suggests that we are witnessing the early stages of inside-out quenching.
We present high-resolution observations (0 2-1 5) of multiple dense gas tracers, HCN and HCO+ (J = 1-0, 3-2, and 4-3), HNC (J = 1-0), and CS (J = 7-6) lines, toward the nearby luminous infrared ...galaxy VV 114 with the Atacama Large Millimeter/submillimeter Array. All lines are robustly detected at the central gaseous filamentary structure, including the eastern nucleus and the overlap region, the collision interface of the progenitors. We found that there is no correlation between star formation efficiency and dense gas fraction, indicating that the amount of dense gas does not simply control star formation in VV 114. We predict the presence of more turbulent and diffuse molecular gas clouds around the overlap region compared to those at the nuclear region, assuming a turbulence-regulated star formation model. The intracloud turbulence at the overlap region might be excited by galaxy-merger-induced shocks, which also explains the enhancement of gas-phase CH3OH abundance previously found there. We also present spatially resolved spectral line energy distributions of HCN and HCO+ for the first time, and derive excitation parameters by assuming optically thin and local thermodynamic equilibrium (LTE) conditions. The LTE model revealed that warmer, HCO+-poorer molecular gas medium is dominated around the eastern nucleus, harboring an active galactic nucleus (AGN). The HCN abundance is remarkably flat (∼3.5 × 10−9) independently of the various environments within the filament of VV 114 (i.e., AGN, star formation, and shock).
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