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1. The ALPINE-ALMA [C II] survey: Little to no evolution in the [C II]–SFR relation over the last 13 Gyr

   https://doi.org/10.1051/0004-6361/202037617  

   Schaerer, D.; Ginolfi, M.; Béthermin, M.; Fudamoto, Y.; Oesch, P. A.; Le Fèvre, O.; Faisst, A.; Capak, P.; Cassata, P.; Silverman, J. D.; et al (November 2020, Astronomy & Astrophysics)

   The [C  II ] 158 μ m line is one of the strongest IR emission lines, which has been shown to trace the star formation rate (SFR) of galaxies in the nearby Universe, and up to z  ∼ 2. Whether this is also the case at higher redshift and in the early Universe remains debated. The ALPINE survey, which targeted 118 star-forming galaxies at 4.4 <   z  <  5.9, provides a new opportunity to examine this question with the first statistical dataset. Using the ALPINE data and earlier measurements from the literature, we examine the relation between the [C  II ] luminosity and the SFR over the entire redshift range from z  ∼ 4 − 8. ALPINE galaxies, which are both detected in [C  II ] and in dust continuum, show good agreement with the local L ([CII])–SFR relation. Galaxies undetected in the continuum by ALMA are found to be over-luminous in [C  II ] when the UV SFR is used. After accounting for dust-obscured star formation, by an amount of SFR(IR) ≈ SFR(UV) on average, which results from two different stacking methods and SED fitting, the ALPINE galaxies show an L ([CII])–SFR relation comparable to the local one. When [C  II ] non-detections are taken into account, the slope may be marginally steeper at high- z , although this is still somewhat uncertain. When compared homogeneously, the z  >  6 [C  II ] measurements (detections and upper limits) do not behave very differently to the z  ∼ 4 − 6 data. We find a weak dependence of L ([CII])/SFR on the Ly α equivalent width. Finally, we find that the ratio L ([CII])/ L IR ∼ (1 − 3) × 10 −3 for the ALPINE sources, comparable to that of “normal” galaxies at lower redshift. Our analysis, which includes the largest sample (∼150 galaxies) of [C  II ] measurements at z  > 4 available so far, suggests no or little evolution of the [C  II ]–SFR relation over the last 13 Gyr of cosmic time. 

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2. The ALPINE-ALMA [CII] survey: Data processing, catalogs, and statistical source properties

   https://doi.org/10.1051/0004-6361/202037649  

   Béthermin, M.; Fudamoto, Y.; Ginolfi, M.; Loiacono, F.; Khusanova, Y.; Capak, P. L.; Cassata, P.; Faisst, A.; Le Fèvre, O.; Schaerer, D.; et al (November 2020, Astronomy & Astrophysics)

   The Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE) targets the [CII] 158 μ m line and the far-infrared continuum in 118 spectroscopically confirmed star-forming galaxies between z  = 4.4 and z  = 5.9. It represents the first large [CII] statistical sample built in this redshift range. We present details regarding the data processing and the construction of the catalogs. We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates (SFRs), we measured the conversion factor from the ALMA 158 μ m rest-frame dust continuum luminosity to the total infrared luminosity ( L IR ) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data. We found that our continuum detections have a median L IR of 4.4 × 10 11 L ⊙ . We also detected 57 additional continuum sources in our ALMA pointings. They are at a lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5 ± 0.2. We measured the 850 μ m number counts between 0.35 and 3.5 mJy, thus improving the current interferometric constraints in this flux density range. We found a slope break in the number counts around 3 mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35 mJy. Finally, we detected the [CII] line in 75 of our targets. Their median [CII] luminosity is 4.8 × 10 8 L ⊙ and their median full width at half maximum is 252 km s −1 . After measuring the mean obscured SFR in various [CII] luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR– L [CII] relations. 

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3. The ALPINE-ALMA [CII] survey: Obscured star formation rate density and main sequence of star-forming galaxies at z  > 4

   https://doi.org/10.1051/0004-6361/202038944  

   Khusanova, Y.; Bethermin, M.; Le Fèvre, O.; Capak, P.; Faisst, A. L.; Schaerer, D.; Silverman, J. D.; Cassata, P.; Yan, L.; Ginolfi, M.; et al (May 2021, Astronomy & Astrophysics)

   Star formation rate (SFR) measurements at z  > 4 have relied mostly on the rest-frame far-ultraviolet (FUV) observations. The corrections for dust attenuation based on the IRX- β relation are highly uncertain and are still debated in the literature. Hence, rest-frame far-infrared (FIR) observations are necessary to constrain the dust-obscured component of the SFR. In this paper, we exploit the rest-frame FIR continuum observations collected by the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) to directly constrain the obscured SFR in galaxies at 4.4 <  z  < 5.9. We used stacks of continuum images to measure average infrared luminosities taking both detected and undetected sources into account. Based on these measurements, we measured the position of the main sequence of star-forming galaxies and the specific SFR (sSFR) at z  ∼ 4.5 and z  ∼ 5.5. We find that the main sequence and sSFR do not significantly evolve between z  ∼ 4.5 and z  ∼ 5.5, as opposed to lower redshifts. We developed a method to derive the obscured SFR density (SFRD) using the stellar masses or FUV-magnitudes as a proxy of FIR fluxes measured on the stacks and combining them with the galaxy stellar mass functions and FUV luminosity functions from the literature. We obtain consistent results independent of the chosen proxy. We find that the obscured fraction of SFRD is decreasing with increasing redshift, but even at z  ∼ 5.5 it constitutes around 61% of the total SFRD. 

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4. Discovery of a Protocluster Core Associated with an Enormous Lya Nebula at z = 2.3

   https://doi.org/10.3847/1538-4357/ac29c6  

   Li, Qiong; Wang, Ran; Dannerbauer, Helmut; Cai, Zheng; Emonts, Bjorn; Prochaska, Jason Xavier; Battaia, Fabrizio Arrigoni; Neri, Roberto; Zhang, Chengpeng; Fan, Xiaohui; et al (December 2021, The Astrophysical Journal)

   Abstract The MAMMOTH-1 nebula at z = 2.317 is an enormous Ly α nebula (ELAN) extending to a ∼440 kpc scale at the center of the extreme galaxy overdensity BOSS 1441. In this paper, we present observations of the CO(3 − 2) and 250 GHz dust-continuum emission from MAMMOTH-1 using the IRAM NOrthern Extended Millimeter Array. Our observations show that CO(3 − 2) emission in this ELAN has not extended widespread emission into the circum- and inter-galactic media. We also find a remarkable concentration of six massive galaxies in CO(3 − 2) emission in the central ∼100 kpc region of the ELAN. Their velocity dispersions suggest a total halo mass of M 200 c ∼ 10 13.1 M ⊙ , marking a possible protocluster core associated with the ELAN. The peak position of the CO(3 − 2) line emission from the obscured AGN is consistent with the location of the intensity peak of MAMMOTH-1 in the rest-frame UV band. Its luminosity line ratio between the CO(3 − 2) and CO(1 − 0) r 3,1 is 0.61 ± 0.17. The other five galaxies have CO(3 − 2) luminosities in the range of (2.1–7.1) × 10 9 K km s −1 pc 2 , with the star-formation rates derived from the 250 GHz continuum of (<36)–224 M ⊙ yr −1 . Follow-up spectroscopic observations will further confirm more member galaxies and improve the accuracy of the halo mass estimation. 

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5. The ALPINE-ALMA [CII] survey: Dust mass budget in the early Universe

   https://doi.org/10.1051/0004-6361/202040258  

   Pozzi, F.; Calura, F.; Fudamoto, Y.; Dessauges-Zavadsky, M.; Gruppioni, C.; Talia, M.; Zamorani, G.; Bethermin, M.; Cimatti, A.; Enia, A.; et al (September 2021, Astronomy & Astrophysics)

   Aims. The dust content of normal galaxies and the dust mass density (DMD) at high- z ( z  > 4) are unconstrained given the source confusion and the sensitivity limitations of previous observations. The ALMA Large Program to INvestigate [CII] at Early times (ALPINE), which targeted 118 ultra-violet (UV)-selected star-forming galaxies at 4.4 <  z  < 5.9, provides a new opportunity to tackle this issue for the first time with a statistically robust dataset. Methods. We exploited the rest-frame far-infrared (FIR) fluxes of 23 galaxies individually detected in their continuum emission, as well as stacked continuum images, to measure the dust content of the 118 UV-selected ALPINE galaxies. We focused on the dust scaling relations and, by comparison with predictions from chemical evolution models, we probed the evolutionary stage of UV-selected galaxies at high- z . By using the observed correlation between the UV luminosity and the dust mass, we estimated the DMD of UV-selected galaxies at z  ∼ 5, weighting the galaxies by means of the UV luminosity function. The derived DMD is compared with the value we estimated from ten ALPINE galaxies blindly detected in the FIR continuum, at the redshift of the ALPINE targets. Results. Our ALMA survey allows the exploration for the first time of the dust content in normal star-forming galaxies at z  > 4 in a statistically robust sample of sources. The comparison of the observed dust scaling relations with chemical evolution models suggests that ALPINE galaxies are not likely progenitors of disc galaxies, but of intermediate- and low-mass proto-spheroids, resulting in present-day bulges of spiral or elliptical galaxies. Interestingly, this conclusion is in line with the independent morphological analysis that shows that the majority (∼70%) of the dust-continuum detected galaxies have a disturbed morphology. The DMD obtained at z  ∼ 5 from UV-selected sources is ∼30% of the value obtained from blind FIR-selected sources, showing that the UV selection misses the most dust-rich, UV-obscured galaxies. 

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