Detections of [O <scp>iii</scp>] 88 μm in two quasars in the reionization epoch

Hashimoto, T.; Inoue, Akio; Tamura, Motohide; Matsuo, Hiroshi; Mawatari, Ken; Yamaguchi, Yuki

doi:10.1093/pasj/psz094

Cited by 60 publications

(95 citation statements)

References 84 publications

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“…Since the [O iii]/[C ii] has been observed to also be similarly extreme in many high-z galaxies (e.g. Laporte et al 2019;Hashimoto et al 2019;Tamura et al 2019;Harikane et al 2020), the results presented here, where we focus on low-Z star-forming galaxies, may eventually be relevant to the understanding of the total molecular gas content and structure in some high-z galaxies.…”

Section: Dwarf Galaxy Survey: Extreme Properties In Low-metallicity Ementioning

confidence: 79%

Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas

Madden

Cormier

Hony

et al. 2020

A&A

132

128

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Context. Molecular gas is a necessary fuel for star formation. The CO (1−0) transition is often used to deduce the total molecular hydrogen but is challenging to detect in low-metallicity galaxies in spite of the star formation taking place. In contrast, the [C ii]λ158 µm is relatively bright, highlighting a potentially important reservoir of H 2 that is not traced by CO (1−0) but is residing in the C +-emitting regions. Aims. Here we aim to explore a method to quantify the total H 2 mass (M H 2) in galaxies and to decipher what parameters control the CO-dark reservoir. Methods. We present Cloudy grids of density, radiation field, and metallicity in terms of observed quantities, such as [O i], [C i], CO (1−0), [C ii], L TIR , and the total M H 2. We provide recipes based on these models to derive total M H 2 mass estimates from observations. We apply the models to the Herschel Dwarf Galaxy Survey, extracting the total M H 2 for each galaxy, and compare this to the H 2 determined from the observed CO (1−0) line. This allows us to quantify the reservoir of H 2 that is CO-dark and traced by the [C ii]λ158 µm. Results. We demonstrate that while the H 2 traced by CO (1−0) can be negligible, the [C ii]λ158 µm can trace the total H 2. We find 70 to 100% of the total H 2 mass is not traced by CO (1−0) in the dwarf galaxies, but is well-traced by [C ii]λ158 µm. The CO-dark gas mass fraction correlates with the observed L [C ii] /L CO(1−0) ratio. A conversion factor for [C ii]λ158 µm to total H 2 and a new CO-to-total-M H 2 conversion factor as a function of metallicity are presented. Conclusions. While low-metallicity galaxies may have a feeble molecular reservoir as surmised from CO observations, the presence of an important reservoir of molecular gas that is not detected by CO can exist. We suggest a general recipe to quantify the total mass of H 2 in galaxies, taking into account the CO and [C ii] observations. Accounting for this CO-dark H 2 gas, we find that the star-forming dwarf galaxies now fall on the Schmidt-Kennicutt relation. Their star-forming efficiency is rather normal because the reservoir from which they form stars is now more massive when introducing the [C ii] measures of the total H 2 compared to the small amount of H 2 in the CO-emitting region.

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Section: Dwarf Galaxy Survey: Extreme Properties In Low-metallicity Ementioning

confidence: 79%

Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas

Madden

Cormier

Hony

et al. 2020

A&A

132

128

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“…A complementary approach to obtaining accurate redshifts is searching for the [CII]158 µm or the [OIII]88 µm line in spectroscopic observations at (sub-)mm frequencies (e.g., Decarli et al 2017;Hashimoto et al 2019;Harikane et al 2020). This approach is particularly promising as it allows for a redshift estimate in those LBG candidates with absent or weak Lyα (Decarli et al 2019) or a fall in redshift windows covered by sky lines (see Fig.…”

Section: Environment Of Early Black Holes: Future Prospectsmentioning

confidence: 99%

Web of the giant: Spectroscopic confirmation of a large-scale structure around the z = 6.31 quasar SDSS J1030+0524

Mignoli

Gilli

Decarli

et al. 2020

A&A

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We report on the spectroscopic confirmation of a large-scale structure around the luminous z = 6.31 quasi-stellar object (QSO) SDSS J1030+0524, powered by a one billion solar mass black hole. The structure is populated by at least six members, namely, four Lyman-break galaxies (LBGs), and two Lyman alpha emitters (LAEs). The four LBGs were identified among a sample of 21 i-band dropouts with zAB < 25.5 selected up to projected separations of 5 physical Mpc (15 arcmin) from the QSO. Their redshifts were determined through multi-object spectroscopic observations at 8−10 m class telescopes lasting up to eight hours. The two LAEs were identified in a 6 h VLT/MUSE observation centered on the QSO. The redshifts of the six galaxies cover the range between 6.129−6.355. Assuming that the peculiar velocities are negligible, this range corresponds to radial separations of ±5 physical Mpc from the QSO, that is comparable to the projected scale of the observed LBG distribution on the sky. We conservatively estimate that this structure is significant at a level > 3.5σ and that the level of the galaxy overdensity is at least 1.5−2 within the large volume sampled (∼780 physical Mpc3). The spectral properties of the six member galaxies (Lyα strength and UV luminosity) are similar to those of field galaxies at similar redshifts. This is the first spectroscopic identification of a galaxy overdensity around a supermassive black hole in the first billion years of the Universe. Our finding lends support to the idea that the most distant and massive black holes form and grow within massive (>1012 M⊙) dark matter halos in large-scale structures and that the absence of earlier detections of such systems is likely due to observational limitations.

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“…This whole domain opened up at high redshift (z > 4) with the ALMA interferometer becoming fully operational when pilot observations took note that detecting [CII] for normal galaxies was ubiquitous even with short on-source exposure times (Capak et al 2015). Galaxies with star formation rates as low as a few M yr −1 have been detected in [CII] at z ∼ 5 (Riechers et al 2014;Capak et al 2015), and [CII] is now detected for galaxies well into the reionization epoch (e.g., Bradač et al 2017;Smit et al 2018;Harikane et al 2018;Fujimoto et al 2019;Sobral et al 2019;Hashimoto et al 2019).…”

Section: Introductionmentioning

confidence: 99%

The ALPINE-ALMA [CII] survey

Fèvre

Béthermin

Faisst

et al. 2020

A&A

170

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The ALMA-ALPINE [CII] survey is aimed at characterizing the properties of a sample of normal star-forming galaxies (SFGs). The ALMA Large Program to INvestigate (ALPINE) features 118 galaxies observed in the [CII]-158 μm line and far infrared (FIR) continuum emission during the period of rapid mass assembly, right after the end of the HI reionization, at redshifts of 4 < z < 6. We present the survey science goals, the observational strategy, and the sample selection of the 118 galaxies observed with ALMA, with an average beam minor axis of about 0.85″, or ∼5 kpc at the median redshift of the survey. The properties of the sample are described, including spectroscopic redshifts derived from the UV-rest frame, stellar masses, and star-formation rates obtained from a spectral energy distribution (SED) fitting. The observed properties derived from the ALMA data are presented and discussed in terms of the overall detection rate in [CII] and FIR continuum, with the observed signal-to-noise distribution. The sample is representative of the SFG population in the main sequence at these redshifts. The overall detection rate in [CII] is 64% for a signal-to-noise ratio (S/N) threshold larger than 3.5 corresponding to a 95% purity (40% detection rate for S/N > 5). Based on a visual inspection of the [CII] data cubes together with the large wealth of ancillary data, we find a surprisingly wide range of galaxy types, including 40% that are mergers, 20% extended and dispersion-dominated, 13% compact, and 11% rotating discs, with the remaining 16% too faint to be classified. This diversity indicates that a wide array of physical processes must be at work at this epoch, first and foremost, those of galaxy mergers. This paper sets a reference sample for the gas distribution in normal SFGs at 4 < z < 6, a key epoch in galaxy assembly, which is ideally suited for studies with future facilities, such as the James Webb Space Telescope (JWST) and the Extremely Large Telescopes (ELTs).

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Detections of [O iii] 88 μm in two quasars in the reionization epoch

Cited by 60 publications

References 84 publications

Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas

Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas

Web of the giant: Spectroscopic confirmation of a large-scale structure around the z = 6.31 quasar SDSS J1030+0524

The ALPINE-ALMA [CII] survey

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