More Like this

1. Fast supermassive black hole growth in the SPT2349–56 protocluster at z = 4.3

   https://doi.org/10.1051/0004-6361/202450225  

   Vito, F; Brandt, W N; Comastri, A; Gilli, R; Ivison, R J; Lanzuisi, G; Lehmer, B D; Lopez, I E; Tozzi, P; Vignali, C (September 2024, Astronomy & Astrophysics)

   Context.Large-scale environment is one of the main physical drivers of galaxy evolution. The densest regions at high redshifts (i.e.z > 2 protoclusters) are gas-rich regions characterised by high star formation activity. The same physical properties that enhance star formation in protoclusters are also thought to boost the growth of supermassive black holes (SMBHs), most likely in heavily obscured conditions. Aims.We aim to test this scenario by probing the active galactic nucleus (AGN) content of SPT2349–56: a massive, gas-rich, and highly star-forming protocluster core atz = 4.3 discovered as an overdensity of dusty star-forming galaxies (DSFGs). We compare our results with data on the field environment and other protoclusters. Methods.We observed SPT2349–56 withChandra(200 ks) and searched for X-ray emission from the known galaxy members. We also performed a spectral energy distribution fitting procedure to derive the physical properties of the discovered AGNs. Results.In the X-ray band, we detected two protocluster members: C1 and C6, corresponding to an AGN fraction among DSFGs in the structure of ≈10%. This value is consistent with other protoclusters atz  =  2 − 4, but higher than the AGN incidence among DSFGs in the field environment. Both AGNs are heavily obscured sources, hosted in star-forming galaxies with ≈3 × 10¹⁰ M_⊙stellar masses. We estimate that the intergalactic medium in the host galaxies contributes to a significant fraction (or even entirely) to the nuclear obscuration. In particular, C1 is a highly luminous (L_X = 2 × 10⁴⁵ erg s⁻¹) and Compton-thick (N_H = 2 × 10²⁴ cm⁻²) AGN, likely powered by aM_BH > 6 × 10⁸ M_⊙SMBH, assuming Eddington-limited accretion. Its high accretion rate suggests that it is in the phase of efficient growth that is generally required to explain the presence of extremely massive SMBHs in the centres of local galaxy clusters. Considering SPT2349–56 and DRC, a similar protocuster atz = 4, and under different assumptions on their volumes, we find that gas-rich protocluster cores atz ≈ 4 enhance the triggering of luminous (logL_X/erg s⁻¹ = 45 − 46) AGNs by three to five orders of magnitude with respect to the predictions from the AGN X-ray luminosity function at a similar redshift in the field environment. We note that this result is not solely driven by the overdensity of the galaxy population in the structures. Conclusions.Our results indicate that gas-rich protoclusters at high redshift boost the growth of SMBHs, which will likely impact the subsequent evolution of the structures. Therefore, they stand as key science targets to obtain a complete understanding of the relation between the environment and galaxy evolution. Dedicated investigations of similar protoclusters are required to definitively confirm this conclusion with a higher statistical significance. 

   more » « less
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. 

   more » « less
3. Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-redshift Obscured Galaxies

   https://doi.org/10.3847/1538-4357/ac2eb4  

   Casey, Caitlin M.; Zavala, Jorge A.; Manning, Sinclaire M.; Aravena, Manuel; Béthermin, Matthieu; Caputi, Karina I.; Champagne, Jaclyn B.; Clements, David L.; Drew, Patrick; Finkelstein, Steven L.; et al (December 2021, The Astrophysical Journal)

   Abstract We present the characteristics of 2 mm selected sources from the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey conducted to date, the Mapping Obscuration to Reionization with ALMA (MORA) survey covering 184 arcmin 2 at 2 mm. Twelve of 13 detections above 5 σ are attributed to emission from galaxies, 11 of which are dominated by cold dust emission. These sources have a median redshift of 〈 z 2 mm 〉 = 3.6 − 0.3 + 0.4 primarily based on optical/near-infrared photometric redshifts with some spectroscopic redshifts, with 77% ± 11% of sources at z > 3 and 38% ± 12% of sources at z > 4. This implies that 2 mm selection is an efficient method for identifying the highest-redshift dusty star-forming galaxies (DSFGs). Lower-redshift DSFGs ( z < 3) are far more numerous than those at z > 3 yet are likely to drop out at 2 mm. MORA shows that DSFGs with star formation rates in excess of 300 M ⊙ yr −1 and a relative rarity of ∼10 −5 Mpc −3 contribute ∼30% to the integrated star formation rate density at 3 < z < 6. The volume density of 2 mm selected DSFGs is consistent with predictions from some cosmological simulations and is similar to the volume density of their hypothesized descendants: massive, quiescent galaxies at z > 2. Analysis of MORA sources’ spectral energy distributions hint at steeper empirically measured dust emissivity indices than reported in typical literature studies, with 〈 β 〉 = 2.2 − 0.4 + 0.5 . The MORA survey represents an important step in taking census of obscured star formation in the universe’s first few billion years, but larger area 2 mm surveys are needed to more fully characterize this rare population and push to the detection of the universe’s first dusty galaxies. 

   more » « less
4. Characterizing the Molecular Gas in Infrared Bright Galaxies with CARMA

   https://doi.org/10.3847/1538-4357/ad7b31  

   Alatalo, Katherine; Petric, Andreea O; Lanz, Lauranne; Rowlands, Kate; U, Vivian; Larson, Kirsten L; Armus, Lee; Barcos-Muñoz, Loreto; Evans, Aaron S; Koda, Jin; et al (November 2024, The Astrophysical Journal)

   Abstract We present the CO(1–0) maps of 28 infrared-bright galaxies from the Great Observatories All-Sky Luminous Infrared Galaxy Survey (GOALS) taken with the Combined Array for Research in Millimeter Astronomy (CARMA). We detect 100 GHz continuum in 16 of the 28 CARMA GOALS galaxies, which trace both active galactic nuclei (AGNs) and compact star-forming cores. The GOALS galaxies show a variety of molecular gas morphologies, though in the majority of cases the average velocity fields show a gradient consistent with rotation. We fit the full continuum spectral energy distributions (SEDs) of each of the sources using eithermagphysor SED3FIT (if there are signs of an AGN) to derive the total stellar mass, dust mass, and SFRs of each object. We adopt a value determined from luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) ofα_CO= ${1.5}_{-0.8}^{+1.3}$M_⊙(K km s⁻¹pc²)⁻¹, which leads to more physical values forf_moland the gas-to-dust ratio. Mergers tend to have the highest gas-to-dust ratios. We assume the cospatiality of the molecular gas and star formation and plot the CARMA GOALS sample on the Schmidt–Kennicutt relation, where we find that they preferentially lie above the line set by normal star-forming galaxies. This hyper-efficiency is likely due to the increased turbulence in these systems, which decreases the freefall time compared to star-forming galaxies, leading to “enhanced” star formation efficiency. Line wings are present in a non-negligible subsample (11/28) of the CARMA GOALS sources and are likely due to outflows driven by AGNs or star formation, gas inflows, or additional decoupled gas components. 

   more » « less
5. SQuIGGL⃗E : Studying Quenching in Intermediate-z Galaxies—Gas, AnguL⃗ar Momentum, and Evolution

   https://doi.org/10.3847/1538-4357/ac404a  

   Suess, Katherine A.; Kriek, Mariska; Bezanson, Rachel; Greene, Jenny E.; Setton, David; Spilker, Justin S.; Feldmann, Robert; Goulding, Andy D.; Johnson, Benjamin D.; Leja, Joel; et al (February 2022, The Astrophysical Journal)

   Abstract We describe the Studying Quenching in Intermediate- z Galaxies: Gas, angu L → ar momentum, and Evolution ( SQuIGG L ⃗ E ) survey of intermediate-redshift post-starburst galaxies. We leverage the large sky coverage of the Sloan Digital Sky Survey to select ∼ 1300 recently quenched galaxies at 0.5 < z ≤ 0.9 based on their unique spectral shapes. These bright, intermediate-redshift galaxies are ideal laboratories to study the physics responsible for the rapid quenching of star formation: they are distant enough to be useful analogs for high-redshift quenching galaxies, but low enough redshift that multiwavelength follow-up observations are feasible with modest telescope investments. We use the Prospector code to infer the stellar population properties and nonparametric star formation histories (SFHs) of all galaxies in the sample. We find that SQuIGG L ⃗ E galaxies are both very massive ( M * ∼ 10 11.25 M ⊙ ) and quenched, with inferred star formation rates ≲1 M ⊙ yr −1 , more than an order of magnitude below the star-forming main sequence. The best-fit SFHs confirm that these galaxies recently quenched a major burst of star formation: >75% of SQuIGG L ⃗ E galaxies formed at least a quarter of their total stellar mass in the recent burst, which ended just ∼200 Myr before observation. We find that SQuIGG L ⃗ E galaxies are on average younger and more burst-dominated than most other z ≲ 1 post-starburst galaxy samples. This large sample of bright post-starburst galaxies at intermediate redshift opens a wide range of studies into the quenching process. In particular, the full SQuIGG L ⃗ E survey will investigate the molecular gas reservoirs, morphologies, kinematics, resolved stellar populations, active galactic nucleus incidence, and infrared properties of this unique sample of galaxies in order to place definitive constraints on the quenching process. 

   more » « less