Abstract
James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) images of the luminous infrared (IR) galaxy VV 114 are presented. This redshift ∼0.020 merger has a western component (VV ...114W) rich in optical star clusters and an eastern component (VV 114E) hosting a luminous mid-IR nucleus hidden at UV and optical wavelengths by dust lanes. With MIRI, the VV 114E nucleus resolves primarily into bright NE and SW cores separated by 630 pc. This nucleus comprises 45% of the 15
μ
m light of VV 114, with the NE and SW cores having IR luminosities,
L
IR
(8 − 1000
μ
m) ∼ 8 ± 0.8 × 10
10
L
⊙
and ∼ 5 ± 0.5 × 10
10
L
⊙
, respectively, and IR densities, Σ
IR
≳ 2 ± 0.2 × 10
13
L
⊙
kpc
−2
and ≳ 7 ± 0.7 × 10
12
L
⊙
kpc
−2
, respectively—in the range of Σ
IR
for the Orion star-forming core and the nuclei of Arp 220. The NE core, previously speculated to have an active galactic nucleus (AGN), has starburst-like mid-IR colors. In contrast, the VV 114E SW core has AGN-like colors. Approximately 40 star-forming knots with
L
IR
∼ 0.02–5 × 10
10
L
⊙
are identified, 28% of which have no optical counterpart. Finally, diffuse emission accounts for 40%–60% of the mid-IR emission. Mostly notably, filamentary polycyclic aromatic hydrocarbon (PAH) emission stochastically excited by UV and optical photons accounts for half of the 7.7
μ
m light of VV 114. This study illustrates the ability of JWST to detect obscured compact activity and distributed PAH emission in the most extreme starburst galaxies in the local universe.
Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty ...star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.
We present a list of candidate gravitationally lensed dusty star-forming galaxies (DSFGs) from the HerMES Large Mode Survey and the Herschel Stripe 82 Survey. Together, these partially overlapping ...surveys cover 372 deg super(2) on the sky. After removing local spiral galaxies and known radio-loud blazars, our candidate list of lensed DSFGs is composed of 77 sources with 500 mum flux densities (S sub(500)) greater than 100 mJy. Such sources are dusty starburst galaxies similar to the first bright sub-millimeter galaxies (SMGs) discovered with SCUBA. We expect a large fraction of this list to be strongly lensed, with a small fraction made up of bright SMG-SMG mergers that appear as hyper-luminous infrared galaxies (L sub(IR)> 10 super(13)L sub(middot in circle)). Thirteen of the 77 candidates have spectroscopic redshifts from CO spectroscopy with ground-based interferometers, putting them at z> 1 and well above the redshift of the foreground lensing galaxies. The surface density of our sample is 0.21 + or - 0.03 deg super(-2). We present follow-up imaging of a few of the candidates to confirm their lensing nature. The sample presented here is an ideal tool for higher-resolution imaging and spectroscopic observations to understand the detailed properties of starburst phenomena in distant galaxies.
ABSTRACT
We present new Institut de Radioastronomie Millimétrique (IRAM) 30 m spectroscopic observations of the ∼88 GHz band, including emission from the
multiplet, HCN (
,
, and
, for a sample of 58 ...local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new IRAM data with literature data and
Spitzer
/IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGNs) and star formation to the mid-infrared luminosity of each system. We find the HCN (1–0) emission to be enhanced in AGN-dominated systems (
/
), compared to composite and starburst-dominated systems (
/
and 0.88, respectively). However, some composite and starburst systems have
/
ratios comparable to those of AGNs, indicating that enhanced HCN emission is not uniquely associated with energetically dominant AGNs. After removing AGN-dominated systems from the sample, we find a linear relationship (within the uncertainties) between log
10
(
) and log
10
(
L
IR
), consistent with most previous findings.
/
L
IR
, typically interpreted as the dense-gas depletion time, appears to have no systematic trend with
L
IR
for our sample of luminous and ultraluminous infrared galaxies, and has significant scatter. The galaxy-integrated
and
emission do not appear to have a simple interpretation in terms of the AGN dominance or the star formation rate, and are likely determined by multiple processes, including density and radiative effects.
We investigate the far-infrared-radio correlation (FRC) of stellar-mass-selected galaxies in the Extended Chandra Deep Field-South using far-infrared (FIR) imaging from Spitzer and radio imaging from ...the Very Large Array and Giant Metre-Wave Radio Telescope. We stack in redshift bins to probe galaxies below the noise and confusion limits. Radio fluxes are K-corrected using observed flux ratios, leading to tentative evidence for an evolution in spectral index. We compare spectral energy distribution (SED) templates of local galaxies for K-correcting FIR fluxes and show that the data are best fitted by a quiescent spiral template (M51) rather than a warm starburst (M82) or ultra-luminous infrared galaxy (Arp 220), implying a predominance of cold dust in massive galaxies at high redshift. In contrast, we measure total infrared luminosities that are consistent with high star-formation rates. We observe that the FRC index (q) does not evolve significantly over z= 0-2 when computed from K-corrected 24- or 160-μm photometry, but that using 70-μm fluxes leads to an apparent decline in q beyond z∼ 1. This suggests some change in the SED at high redshift, either a steepening of the spectrum at rest-frame ∼25-35 μm or a deficiency at ∼70 μm leading to a drop in the total infrared-radio ratios. We compare our results to other work in the literature and find synergies with recent findings on the high-redshift FRC, high specific star formation rates of massive galaxies and the cold dust temperatures in these galaxies.
Abstract
We report the detection of CO(1–0) line emission from seven Planck and Herschel selected hyper luminous (${L_{\rm IR (8{\rm -}1000{\mu m})} > 10^{13}\,\, {\rm L}_{{\odot }} }$) infrared ...galaxies with the Green Bank Telescope (GBT). CO(1–0) measurements are a vital tool to trace the bulk molecular gas mass across all redshifts. Our results place tight constraints on the total gas content of these most apparently luminous high-z star-forming galaxies (apparent IR luminosities of LIR > 1013 − 14 L⊙), while we confirm their predetermined redshifts measured using the Large Millimeter Telescope, LMT (zCO = 1.33–3.26). The CO(1–0) lines show similar profiles as compared to Jup = 2–4 transitions previously observed with the LMT. We report enhanced infrared to CO line luminosity ratios of $\langle L_{\rm IR} / L^{\prime }_{\rm CO(1{\rm -}0)} \rangle \ = 110 \pm 22 {\, }\,\, {\rm L_{{\odot }} (K {\, } km {\, } s^{-1} {\, } pc^{-2})^{-1} }$ compared to normal star-forming galaxies, yet similar to those of well-studied IR-luminous galaxies at high-z. We find average brightness temperature ratios of 〈 r21〉 = 0.93 (2 sources), 〈 r31〉 = 0.34 (5 sources), and 〈 r41〉 = 0.18 (1 source). The r31 and r41 values are roughly half the average values for SMGs. We estimate the total gas mass content as ${\rm \mu M_{H2} = (0.9{\rm -}27.2) \times 10^{11} (\alpha _{\rm CO}/0.8){\, }{\rm M}_{{\odot }}}$, where μ is the magnification factor and αCO is the CO line luminosity to molecular hydrogen gas mass conversion factor. The rapid gas depletion times, ${\rm \langle \tau _{\rm depl} \rangle = 80}$ Myr, reveal vigorous starburst activity, and contrast the Gyr depletion time-scales observed in local, normal star-forming galaxies.
We present IRAM-30 m Telescope 12CO and 13CO observations of a sample of 55 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe. This sample is a subset of the Great ...Observatory All-Sky LIRG Survey (GOALS), for which we use ancillary multi-wavelength data to better understand their interstellar medium and star formation properties. Fifty-three (96%) of the galaxies are detected in 12CO, and 29 (52%) are also detected in 13CO above a 3σ level. The median full width at zero intensity (FWZI) velocity of the CO line emission is 661 km s−1, and ∼54% of the galaxies show a multi-peak CO profile. Herschel photometric data is used to construct the far-IR spectral energy distribution of each galaxy, which are fit with a modified blackbody model that allows us to derive dust temperatures and masses, and infrared luminosities. We make the assumption that the gas-to-dust mass ratio of (U)LIRGs is comparable to local spiral galaxies with a similar stellar mass (i.e., gas/dust of mergers is comparable to their progenitors) to derive a CO-to-H2 conversion factor of ⟨α⟩ = 1.8−0.8+1.3 M⊙ ⟨ α ⟩ = 1 . 8 − 0.8 + 1.3 M ⊙ $ \langle\alpha\rangle=1.8^{+1.3}_{-0.8}\,M_\odot $ (K km s−1 pc2)−1; such a value is comparable to that derived for (U)LIRGs based on dynamical mass arguments. We derive gas depletion times of 400 − 600 Myr for the (U)LIRGs, compared to the 1.3 Gyr for local spiral galaxies. Finally, we re-examine the relationship between the 12CO/13CO ratio and dust temperature, confirming a transition to elevated ratios in warmer systems.
Aims. We derive the evolution of the infrared luminosity function (LF) over the last 4/5ths of cosmic time using deep 24 and 70 μm imaging of the GOODS North and South fields. Methods. We use an ...extraction technique based on prior source positions at shorter wavelengths to build the 24 and 70 μm source catalogs. The majority (93%) of the sources have a spectroscopic (39%) or a photometric redshift (54%) and, in our redshift range of interest (i.e., 1.3 < z < 2.3) s20% of the sources have a spectroscopic redshift. To extend our study to lower 70 μm luminosities we perform a stacking analysis and we characterize the observed L24/(1 + z) vs. L70/(1 + z) correlation. Using spectral energy distribution (SED) templates which best fit this correlation, we derive the infrared luminosity of individual sources from their 24 and 70 μm luminosities. We then compute the infrared LF at zs1.55 ± 0.25 and zs2.05 ± 0.25. Results. We observe the break in the infrared LF up to zs2.3. The redshift evolution of the infrared LF from z = 1.3 to z = 2.3 is consistent with a luminosity evolution proportional to (1 + z)1.0 ± 0.9 combined with a density evolution proportional to (1 + z)−1.1 ± 1.5. At zs2, luminous infrared galaxies (LIRGs: 1011L⊙ < LIR < 1012 L⊙) are still the main contributors to the total comoving infrared luminosity density of the Universe. At zs2, LIRGs and ultra-luminous infrared galaxies (ULIRGs: 1012L⊙ < LIR) account for s49% and s17% respectively of the total comoving infrared luminosity density of the Universe. Combined with previous results using the same strategy for galaxies at z < 1.3 and assuming a constant conversion between the infrared luminosity and star-formation rate (SFR) of a galaxy, we study the evolution of the SFR density of the Universe from z = 0 to z = 2.3. We find that the SFR density of the Universe strongly increased with redshift from z = 0 to z = 1.3, but is nearly constant at higher redshift out to z = 2.3. As part of the online material accompanying this article, we present source catalogs at 24 μm and 70 μm for both the GOODS-North and -South fields.
Examining a sample of massive galaxies at 1.4 < z < 2.5 with unk < 22 from GOODS, we compare photometry from Spitzer at mid- and far-IR to submillimeter, radio, and rest-frame UV wavelengths, to test ...the agreement between different tracers of star formation rates (SFRs) and to explore the implications for galaxy assembly. For z similar to 2 galaxies with moderate luminosities ( unk < 10 super(11) L unk), we find that the SFR can be estimated consistently from the multiwavelength data based on local luminosity correlations. However, 20%-30% of massive galaxies, and nearly all those with unk 10 super(11) L unk, show a mid-IR excess that is likely due to the presence of obscured active nuclei, as shown in a companion paper. There is a tight and roughly linear correlation between stellar mass and SFR for 24 mu m-detected galaxies. For a given mass, the SFR at z = 2 was larger by a factor of similar to 4 and similar to 30 relative to that in star-forming galaxies at z = 1 and 0, respectively. Typical ultraluminous infrared galaxies (ULIRGs) at z = 2 are relatively "transparent" to ultraviolet light, and their activity is long lived ( unk400 Myr), unlike that in local ULIRGs and high-redshift submillimeter-selected galaxies. ULIRGs are the common mode of star formation in massive galaxies at z = 2, and the high duty cycle suggests that major mergers are not the dominant trigger for this activity. Current galaxy formation models underpredict the normalization of the mass-SFR correlation by about a factor of 4 and the space density of ULIRGs by an order of magnitude but give better agreement for z > 1.4 quiescent galaxies.
ABSTRACT
Using the Eight MIxer Receiver (EMIR) instrument on the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope, we conducted a spectroscopic redshift search of seven zphot ∼ 4 ...submillimetre bright galaxies selected from the Herschel Bright Sources sample with fluxes at 500 μm greater than 80 mJy. For four sources, we obtained spectroscopic redshifts between 3.4 < z < 4.1 through the detection of multiple CO-spectral lines with J ≥ 3. Later, we detected low-J transitions for two of these sources with the Green Bank Telescope including the CO(1–0) transition. For the remaining three sources, more data are needed to determine the spectroscopic redshift unambiguously. The measured CO luminosities and line widths suggest that all these sources are gravitationally lensed. These observations demonstrate that the 2 mm window is indispensable to confirm robust spectroscopic redshifts for z < 4 sources. Finally, we present an efficient graphical method to correctly identify spectroscopic redshifts.
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