Constraints on high-J CO emission lines in z ∼ 6 quasars

Carniani, Stefano; Gallerani, S.; Vallini, L.; Pallottini, Andrea; Tazzari, Marco; Ferrara, Andrea; Maiolino, R.; Cicone, C.; Feruglio, C.; Neri, R.; D’Odorico, V.; Wang, R.; Li, J.

doi:10.1093/mnras/stz2410

Cited by 33 publications

(30 citation statements)

References 87 publications

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“…We have also estimated the extent of the FIR line emission by performing a 2D-Gaussian fitting of the [CII] flux map with the CASA task imfit. In addition to the image plane analysis, we have also performed the size measurements on the uv plane by collapsing the spectral channels around the line peak and following the procedure explained in (Carniani et al 2019), which adopts the GALARIO package Tazzari et al (2018). The two measurements are in agreement within the errors.…”

Section: Observations and Data Analysismentioning

confidence: 99%

Missing [C ii] emission from early galaxies

Carniani

Ferrara

Maiolino

et al. 2020

Monthly Notices of the Royal Astronomical Society

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ALMA observations have revealed that [C$\scriptstyle \rm II$]158μm line emission in high-z galaxies is ≈2 − 3 × more extended than the UV continuum emission. Here we explore whether surface brightness dimming (SBD) of the [C$\scriptstyle \rm II$] line is responsible for the reported [C$\scriptstyle \rm II$] deficit, and the large L[OIII]/L[CII] luminosity ratio measured in early galaxies. We first analyse archival ALMA images of nine z > 6 galaxies observed in both [C$\scriptstyle \rm II$] and [O$\scriptstyle \rm III$]. After performing several uv-tapering experiments to optimize the identification of extended line emission, we detect [C$\scriptstyle \rm II$] emission in the whole sample, with an extent systematically larger than the [O$\scriptstyle \rm III$] emission. Next, we use interferometric simulations to study the effect of SBD on the line luminosity estimate. About 40% of the extended [C$\scriptstyle \rm II$] component might be missed at an angular resolution of 0.8″, implying that L[CII] is underestimated by a factor ≈2 in data at low (<7) signal-to-noise ratio. By combining these results, we conclude that L[CII] of z > 6 galaxies lies, on average, slightly below the local L[CII] − SFR relation (Δz = 6 − 9 = −0.07 ± 0.3), but within the intrinsic dispersion of the relation. SBD correction also yields L[OIII]/L[CII] < 10, i.e. more in line with current hydrodynamical simulations.

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Section: Observations and Data Analysismentioning

confidence: 99%

Missing [C ii] emission from early galaxies

Carniani

Ferrara

Maiolino

et al. 2020

Monthly Notices of the Royal Astronomical Society

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155

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“…Error bars are estimated by propagating the error of the line flux on L CO , and assuming a variation of 0.5 dex for L FIR . Also shown are the values obtained for high-redshift SMGs/quasi-stellar objects (QSOs) as the green and grey filled circles in case of CO(9−8) and CO(10−9) transitions, respectively(Carilli & Walter 2013;ALMA Partnership et al 2015;Carniani et al 2019). Right-hand panel: [C II] as a function of FIR luminosity for several kinds of objects at different redshifts.…”

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confidence: 99%

The ALPINE−ALMA [C ii] Survey: on the nature of an extremely obscured serendipitous galaxy

Romano

Cassata

Morselli

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We report the serendipitous discovery of a dust-obscured galaxy observed as part of the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [C ii] at Early times (ALPINE). While this galaxy is detected both in line and continuum emissions in ALMA Band 7, it is completely dark in the observed optical/near-infrared bands and only shows a significant detection in the UltraVISTA Ks band. We discuss the nature of the observed ALMA line, that is [C ii] at $z$ ∼ 4.6 or high-J CO transitions at $z$ ∼ 2.2. In the first case, we find a [C ii]/FIR luminosity ratio of $\mathrm{log}{(L_{[\mathrm{ C}\, \rm {\small {II}}]}/L_{\mathrm{ FIR}})} \sim -2.5$, consistent with the average value for local star-forming galaxies (SFGs). In the second case instead, the source would lie at larger CO luminosities than those expected for local SFGs and high-z submillimetre galaxies. At both redshifts, we derive the star formation rate (SFR) from the ALMA continuum and the physical parameters of the galaxy, such as the stellar mass (M*), by fitting its spectral energy distribution. Exploiting the results of this work, we believe that our source is a ‘main-sequence’, dusty SFG at $z$ = 4.6 (i.e. [C ii] emitter) with $\mathrm{log(SFR/M_{\odot }\, yr^{-1})}\sim 1.4$ and log(M*/M⊙) ∼ 9.9. As a support to this scenario our galaxy, if at this redshift, lies in a massive protocluster recently discovered at $z$ ∼ 4.57, at only ∼1 proper Mpc from its centre. This work underlines the crucial role of the ALPINE survey in making a census of this class of objects, in order to unveil their contribution to the global SFR density at the end of the Reionization epoch.

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“…This model also assumes no contributions from separate MIR (e.g., Casey 2012), radio (e.g., Yun & Carilli 2002), or higher frequency (e.g., Leitherer et al 1999) components. In particular, some studies have found that the addition of a MIR power law to a MBB results in a better fit to the FIR SEDs of some galaxies (e.g., Ibar et al 2015;Faisst et al 2020;Reuter et al 2020) Even though the MBB function is indeed simple, it has been found to fit dust SEDs very well (e.g., Bianchi 2013;Jiménez-Andrade et al 2018;Carniani et al 2019;Crocker et al 2019;Lamperti et al 2019). The frequency domain of our model is also controlled to ensure that the contributions from higher and lower frequency components are negligible.…”

Section: Discussion Of Uncertaintiesmentioning

confidence: 99%

“…Optical Thickness: As discussed in Section 4.1.1, we make no assumption on the optical thickness of our source, and therefore use a generalized MBB (similar to e.g., Leech et al 2001;Cortzen et al 2020), rather than one that assumes τ ν << 1 (e.g., Carniani et al 2019;Lamperti et al 2019;Valentino et al 2020). To test whether this source is optically thin, we apply equation 2 to the data in Table 1, using our best-fit dust mass and emissivity index.…”

Section: Discussion Of Uncertaintiesmentioning

confidence: 99%

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Gas and star formation from HD and dust emission in a strongly lensed galaxy

Jones

Maiolino

Caselli

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The molecular gas content of high-redshift galaxies is a highly sought-after property. However, H2 is not directly observable in most environments, so its mass is probed through other emission lines (e.g., CO, [CI], [CII]), or through a gas-to-dust ratio. Each of these methods depends on several assumptions, and are best used in parallel. In this work, we extend an additional molecular gas tracer to high-redshift studies by observing hydrogen deuteride (HD) emission in the strongly lensed z = 5.656 galaxy SPT0346-52 with ALMA. While no HD(1-0) emission is detected, we are able to place an upper limit on the gas mass of $\rm M_{H_2}<6.4\times 10^{11}\, M_{\odot }$. This is used to find a limit on the $L^{\prime }_{CO}$ conversion factor of $\rm \alpha _{CO}<5.8$ M⊙(K km s−1 pc2)−1. In addition, we construct the most complete spectral energy distribution (SED) of this source to date, and fit it with a single-temperature modified blackbody using the nested sampling code MultiNest, yielding a best-fit dust mass Mdust = 108.92 ± 0.02 M⊙, dust temperature 78.6 ± 0.5 K, dust emissivity spectral index β = 1.81 ± 0.03, and star formation rate SFR = 3800 ± 100 M⊙ year−1. Using the continuum flux densities to estimate the total gas mass of the source, we find M$_{H_2}<2.4\times 10^{11}$ M⊙, assuming sub-solar metallicity. This implies a CO conversion factor of αCO < 2.2, which is between the standard values for MW-like galaxies and starbursts. These properties confirm that SPT0346-52 is a heavily starbursting, gas rich galaxy.

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Constraints on high-J CO emission lines in z ∼ 6 quasars

Cited by 33 publications

References 87 publications

Missing [C ii] emission from early galaxies

Missing [C ii] emission from early galaxies

The ALPINE−ALMA [C ii] Survey: on the nature of an extremely obscured serendipitous galaxy

Gas and star formation from HD and dust emission in a strongly lensed galaxy

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