FIR-luminous [C ii] Emitters in the ALMA-SCUBA-2 COSMOS Survey (AS2COSMOS): The Nature of Submillimeter Galaxies in a 10 Comoving Megaparsec-scale Structure at z ∼ 4.6

Mitsuhashi, Ikki; Matsuda, Yoshihisa; Smail, Ian; Hayatsu, Natsuki H.; Simpson, J. M.; Swinbank, A. M.; Umehata, Hideki; Dudzevičiūtė, U.; Birkin, Jack E.; Ikarashi, Soh; Chen, Chian-Chou; Tadaki, Ken-ichi; Yajima, Hidenobu; Harikane, Yuichi; Inami, Hanae; Chapman, Scott; Hatsukade, Bunyo; Iono, Daisuke; Bunker, A. J.; Ao, Yiping; Saito, Tomoki; Ueda, Junko; Sakamoto, Seiichi

doi:10.3847/1538-4357/abcc72

“…To investigate whether there is a specific property that explains its Planck significant detection, we compare G237 with other protoclusters situated in the Cosmos field at z∼2-2.5. There are other protoclusters found at much higher redshifts (e.g., Capak et al 2011;Pavesi et al 2018;Lemaux et al 2018;Mitsuhashi et al 2021), but we do not analyze them as the Planck high-z source selection is not tailored to find protoclusters at z 4.…”

Section: Structure Properties That Make a Planck High-z Sourcementioning

confidence: 99%

Spectroscopic observations of PHz G237.01+42.50: A galaxy protocluster at z = 2.16 in the Cosmos field

Polletta

¹

,

Soucail

²

,

Dole

³

et al. 2021

A&A

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The Planck satellite has identified more than 2000 protocluster candidates with extreme star formation rates (SFRs). Here, we present the spectroscopic identification of a Planck-selected protocluster located in the Cosmos field, PHz G237.01+42.50. PHz G237.01+42.50 contains a galaxy overdensity of 31 spectroscopically identified galaxies at z ≃ 2.16 (significant at 5.4σ) in a 10′ × 11′ region. The overdensity contains two substructures or protoclusters at ⟨z⟩ ≃ 2.16 and 2.195 with estimated halo masses at z = 0 of ∼5–6 × 1014 M⊙, roughly consistent with Virgo-type clusters. The overdensity total SFR, ∼4000 M⊙ yr−1, is higher than predicted by simulations but much smaller than the SFR derived from the Planck data (i.e., 10 173 M⊙ yr−1). The analysis of the Herschel data in the field, in combination with the available ancillary data, shows that such a difference is due to an effect of source alignment along the line of sight that produces a 5σ overdensity of red Herschel sources in the field. We analyze the members’ ultraviolet (UV) spectra and UV-far-infrared spectral energy distributions to derive their SFR, stellar mass, and metallicity. Galaxy members include blue star-forming galaxies and Active galactic nuclei (AGN) with SFRs and stellar masses consistent with the main sequence. Active galactic nuclei, identified through optical spectroscopy or X-ray data, represent a significant fraction (20 ± 10%) of all members of the protocluster at z = 2.16, and they are powerful enough to produce radiative feedback. The core of this protocluster, besides being denser, includes members that are, on average, more massive and star-forming and contains a larger fraction of AGN and Herschel-detected galaxies than the full sample, suggesting an environmental effect on galaxy growth. A comparison between PHz G237.01+42.50 and other protoclusters in the literature at similar redshifts reveals some common traits and differences that reflect both observational biases and a diversity in intrinsic properties that is not yet fully understood.

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“…These ALMA-detected H-faint galaxies, found in abundance (∼530 deg −2 by Wang et al 2019), are proposed as a critical tracer of the early phase of massive galaxy formation history. However, most of their physical properties still remain highly uncertain except for rare cases with spectroscopic confirmations (e.g., Walter et al 2012;Wang et al 2019;Umehata et al 2020;Zhou et al 2020;Caputi et al 2021;Mitsuhashi et al 2021) due to their non-detections and faintness at most wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters

Sun

¹

,

Egami

²

,

Pérez‐González

³

et al. 2021

ApJ

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We present a Spitzer/IRAC survey of H-faint (H 160 ≳ 26.4, < 5σ) sources in 101 lensing cluster fields. Across a CANDELS/Wide-like survey area of ∼648 arcmin2 (effectively ∼221 arcmin2 in the source plane), we have securely discovered 53 sources in the IRAC Channel-2 band (CH2, 4.5 μm; median CH2 = 22.46 ± 0.11 AB mag) that lack robust HST/WFC3-IR F160W counterparts. The most remarkable source in our sample, namely ES-009 in the field of Abell 2813, is the brightest H-faint galaxy at 4.5 μm known so far (CH2 = 20.48 ± 0.03 AB mag). We show that the H-faint sources in our sample are massive (median M star = 1010.3±0.3 M ⊙), star-forming (median star formation rate = 100 − 40 + 60 M ⊙ yr−1), and dust-obscured (A V = 2.6 ± 0.3) galaxies around a median photometric redshift of z = 3.9 ± 0.4. The stellar continua of 14 H-faint galaxies can be resolved in the CH2 band, suggesting a median circularized effective radius (R e,circ; lensing corrected) of 1.9 ± 0.2 kpc and <1.5 kpc for the resolved and whole samples, respectively. This is consistent with the sizes of massive unobscured galaxies at z ∼ 4, indicating that H-faint galaxies represent the dusty tail of the distribution of a wider galaxy population. Comparing with the ALMA dust continuum sizes of similar galaxies reported previously, we conclude that the heavy dust obscuration in H-faint galaxies is related to the compactness of both stellar and dust continua (R e,circ ∼ 1 kpc). These H-faint galaxies make up 16 − 7 + 13 % of the galaxies in the stellar-mass range of 1010 − 1011.2 M ⊙ at z = 3 ∼ 5, contributing to 8 − 4 + 8 % of the cosmic star formation rate density in this epoch and likely tracing the early phase of massive galaxy formation.

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“…To determine redshifts, the target SMGs are grouped into three categories; SMGs with multiple line detection, those with only one line detection, and then finally those that do not have emission line detection. Other work in the literature are referenced to aid the redshift determinations, in particular those from Jiménez-Andrade et al ( 2020) and Mitsuhashi et al (2021). The category to which each SMG belongs is given in Table 2.…”

Section: Redshift Determinationmentioning

confidence: 99%

“…Simpson et al (2020) andMitsuhashi et al (2021) both reported the redshift of AS2COS0001.2 to be 4.635±0.001 based on the CII line.…”

mentioning

confidence: 99%

An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS field (AS2COSPEC): Survey Description and First Results

Chen,

Liao,

Smail

et al. 2021

Preprint

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We introduce an ALMA band 3 spectroscopic survey, targeting the brightest submillimeter galaxies (SMGs) in the COSMOS field. Here we present the first results based on the 18 primary SMGs that have 870 µm flux densities of S 870 = 12.4 − 19.3 mJy and are drawn from a parent sample of 260 ALMA-detected SMGs from the AS2COSMOS survey. We detect emission lines in 17 and determine their redshifts to be in the range of z = 2 − 5 with a median of 3.2 ± 0.3. We confirm that SMGs with brighter S 870 are located at higher redshifts. The data additionally cover five fainter companion SMGs, and we obtain line detection in one. Together with previous studies, our results indicate that for SMGs that satisfy our selection, their brightest companion SMGs are physically associated with their corresponding primary SMGs in ≥ 40% of the time, suggesting that mergers play a role in the triggering of star formation. By modeling the foreground gravitational fields, < 10% of the primary SMGs can be strongly lensed with a magnification µ > 2. We determine that about 90% of the primary SMGs have lines that are better described by double Gaussian profiles, and the median separation of the two Gaussian peaks is 430±40 km s −1 . This allows estimates of an average baryon mass, which together with the line dispersion measurements puts our primary SMGs on the similar mass-σ correlation found on local early-type galaxies. Finally, the number density of our z > 4 primary SMGs is found to be 1 × 10 −6 cMpc −3 , suggesting that they can be the progenitors of z ∼ 3 − 4 massive quiescent galaxies.

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FIR-luminous [C ii] Emitters in the ALMA-SCUBA-2 COSMOS Survey (AS2COSMOS): The Nature of Submillimeter Galaxies in a 10 Comoving Megaparsec-scale Structure at z ∼ 4.6

Cited by 17 publications

References 112 publications

Spectroscopic observations of PHz G237.01+42.50: A galaxy protocluster at z = 2.16 in the Cosmos field

Spectroscopic observations of PHz G237.01+42.50: A galaxy protocluster at z = 2.16 in the Cosmos field

Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters

An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS field (AS2COSPEC): Survey Description and First Results

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