Very Compact Millimeter Sizes for Composite Star-forming/AGN Submillimeter Galaxies

Deep surveys with the Atacama Large Millimeter Array (ALMA) have uncovered a population of dusty star-forming galaxies which are faint or even undetected at optical to near-infrared wavelengths. Their faintness at short wavelengths makes the detailed characterization of the population challenging. Here we present a spectroscopic redshift identification and a characterization of one of these near-infrared-dark galaxies discovered by an ALMA deep survey. The detection of [C I](1–0) and CO(4–3) emission lines determines the precise redshift of the galaxy, ADF22.A2, to be z = 3.9913 ± 0.0008. On the basis of a multi-wavelength analysis, ADF22.A2 is found to be a massive, star-forming galaxy with a stellar mass of M∗ = 1.1−0.6+1.3 × 1011 M⊙ and SFR = 430−150+230 M⊙ yr−1. The molecular gas mass was derived to be M(H2)[CI] = (5.9 ± 1.5)×1010 M⊙, indicating a gas fraction of ≈35%, and the ratios of L[CI](1−0)/LIR and L[CI](1−0)/LCO(4−3) suggest that the nature of the interstellar medium in ADF22.A2 is in accordance with those of other bright submillimeter galaxies. The properties of ADF22.A2, including the redshift, star-formation rate, stellar mass, and depletion time scale (τdep ≈ 0.1−0.2 Gyr), also suggest that ADF22.A2 has the characteristics expected for the progenitors of quiescent galaxies at z ≳ 3. Our results demonstrate the power of ALMA contiguous mapping and line scan, which help us to obtain an unbiased view of galaxy formation in the early Universe.

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What is driving the evolution of the far-infrared radio correlation?

Zbornik Matice srpske za prirodne nauke ◽

10.2298/zmspn1937009p ◽

2019 ◽

pp. 9-16

Author(s):

Marina Pavlovic ◽

Tijana Prodanovic

Keyword(s):

Radio Emission ◽

Large Range ◽

High Redshift ◽

Far Infrared ◽

Morphological Type ◽

Interacting Galaxies ◽

Disk Galaxies ◽

Star Forming ◽

Submillimeter Galaxies ◽

Small Dispersion

Far infrared-radio correlation represents a linear relationship between far-infrared (FIR) and radio emission in star-forming galaxies. Previous observations have confirmed that this correlation is maintained over a large range of redshift and does not evolve, although a small dispersion is present. However, some of more recent observations at high redshift have shown the opposite. The question that arises is - what is driving this evolution? In this paper we investigate the possibility that galaxy morphology is the answer to this question. A sample of 37 submillimeter galaxies (SMGs) is analyzed. The observation and morphological class of these galaxies has previously been published. We examined FIR-radio correlation in galaxies of different morphological type in this sample and found that for star-forming disk galaxies correlation is stable and does not evolve and for irregular and interacting galaxies we find some hints of evolution.

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Extended Hα over compact far-infrared continuum in dusty submillimeter galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936286 ◽

2020 ◽

Vol 635 ◽

pp. A119 ◽

Cited By ~ 4

Author(s):

Chian-Chou Chen ◽

C. M. Harrison ◽

I. Smail ◽

A. M. Swinbank ◽

O. J. Turner ◽

...

Keyword(s):

Near Infrared ◽

Far Infrared ◽

Young Star ◽

Spectral Energy ◽

Star Forming ◽

Very Large Telescope ◽

Submillimeter Galaxies ◽

The Difference ◽

Using Data ◽

Integral Field

By using data from the Atacama Large Millimeter/submillimeter Array and near-infrared (NIR) integral field spectrographs, including both Spectrograph for INtegral Field Observations in the Near Infrared and K-band Multi Object Spectrograph on the Very Large Telescope, we investigate the two-dimensional distributions of Hα and rest-frame far-infrared (FIR) continuum in six submillimeter galaxies (SMGs) at z ∼ 2. At a similar spatial resolution (∼0.″5 FWHM; ∼4.5 kpc at z = 2), we find that the half-light radius of Hα is significantly larger than that of the FIR continuum in half of the sample, and on average Hα is a median factor of 2.0 ± 0.4 larger. Having explored various ways to correct for the attenuation, we find that the attenuation-corrected Hα-based star-formation rates (SFRs) are systematically lower than the infrared (IR)-based SFRs by at least a median factor of 3 ± 1, which cannot be explained by the difference in half-light radius alone. In addition, we find that in 40% of cases the total V-band attenuation (AV) derived from energy balance modeling of the full ultraviolet (UV)-to-FIR spectral energy distributions (SEDs) is significantly higher than what is derived from SED modeling using only the UV-to-NIR part of the SEDs, and the discrepancy appears to increase with increasing total infrared luminosity. Finally, in considering all of our findings along with the studies in the literature, we postulate that the dust distributions in SMGs, and possibly also in less IR luminous z ∼ 2 massive star-forming galaxies, can be decomposed into the following three main components: the diffuse dust heated by older stellar populations, the more obscured and extended young star-forming H II regions, and the heavily obscured central regions that have a low filling factor but dominate the infrared luminosity in which the majority of attenuation cannot be probed via UV-to-NIR emissions.

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Milky Way–like Gas Excitation in an Ultrabright Submillimeter Galaxy at z = 1.6

The Astrophysical Journal ◽

10.3847/2041-8213/ac2eba ◽

2021 ◽

Vol 923 (2) ◽

pp. L27

Author(s):

N. Sulzenauer ◽

H. Dannerbauer ◽

A. Díaz-Sánchez ◽

B. Ziegler ◽

S. Iglesias-Groth ◽

...

Keyword(s):

Star Formation ◽

Milky Way ◽

Formation Rate ◽

Galaxy Cluster ◽

Star Formation History ◽

Star Forming ◽

Line Intensities ◽

Formation Mode ◽

Formation History ◽

Submillimeter Galaxies

Abstract Based on observations with the IRAM 30 m and Yebes 40 m telescopes, we report evidence of the detection of Milky Way–like, low-excitation molecular gas, up to the transition CO(J = 5–4), in a distant, dusty star-forming galaxy at z CO = 1.60454. WISE J122651.0+214958.8 (alias SDSS J1226, the Cosmic Seahorse), is strongly lensed by a foreground galaxy cluster at z = 0.44 with a source magnification of μ = 9.5 ± 0.7. This galaxy was selected by cross-correlating near-to-mid-infrared colors within the full-sky AllWISE survey, originally aiming to discover rare analogs of the archetypical strongly lensed submillimeter galaxy SMM J2135–0102, the Cosmic Eyelash. We derive an apparent (i.e., not corrected for lensing magnification) rest-frame 8–1000 μm infrared luminosity of μ L IR = 1.66 − 0.04 + 0.04 × 10 13 L ⊙ and apparent star formation rate μSFRIR = 2960 ± 70 M ⊙ yr−1. SDSS J1226 is ultrabright at S 350μm ≃ 170 mJy and shows similarly bright low-J CO line intensities as SMM J2135–0102, however, with exceptionally small CO(J = 5–4) intensity. We consider different scenarios to reconcile our observations with typical findings of high-z starbursts, and speculate about the presence of a previously unseen star formation mechanism in cosmic noon submillimeter galaxies. In conclusion, the remarkable low line luminosity ratio r 5,2 = 0.11 ± 0.02 is best explained by an extended, main-sequence star formation mode—representing a missing link between starbursts to low-luminosity systems during the epoch of peak star formation history.

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Neutral carbon and highly excited CO in a massive star-forming main sequence galaxy at z = 2.2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935148 ◽

2019 ◽

Vol 628 ◽

pp. A104 ◽

Cited By ~ 3

Author(s):

Drew Brisbin ◽

Manuel Aravena ◽

Emanuele Daddi ◽

Helmut Dannerbauer ◽

Roberto Decarli ◽

...

Keyword(s):

Star Formation ◽

Main Sequence ◽

Far Infrared ◽

Molecular Gas ◽

Low Velocity ◽

Star Forming ◽

Luminous Infrared Galaxies ◽

Submillimeter Galaxies ◽

Co Emission ◽

Gas Component

We used the Plateau De Bure Interferometer to observe multiple CO and neutral carbon transitions in a z = 2.2 main sequence disk galaxy, BX610. Our observation of CO(7-6), CO(4-3), and both far-infrared (FIR) [CI] lines complements previous observations of Hα and low-J CO, and reveals a galaxy that is vigorously forming stars with UV fields (Log(GG0−1) ≲ 3.25); although less vigorously than local ultra-luminous infrared galaxies or most starbursting submillimeter galaxies in the early universe. Our observations allow new independent estimates of the cold gas mass which indicate Mgas ∼ 2 × 1011 M⊙, and suggest a modestly larger αCO value of ∼8.2. The corresponding gas depletion timescale is ∼1.5 Gyr. In addition to gas of modest density (Log(n cm3) ≲ 3) heated by star formation, BX610 shows evidence for a significant second gas component responsible for the strong high-J CO emission. This second component might either be a high-density molecular gas component heated by star formation in a typical photodissociation region, or could be molecular gas excited by low-velocity C shocks. The CO(7-6)-to-FIR luminosity ratio we observe is significantly higher than typical star-forming galaxies and suggests that CO(7-6) is not a reliable star-formation tracer in this galaxy.

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