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ALMA¹²CO(1-0) observations of 42 star-forming regions located outside the disc of the Virgo Cluster galaxy NGC 4254 within an H Igas tail produced during the galaxy’s interaction with another cluster member have revealed the presence of ten giant molecular clouds (GMCs) in four of these regions. All of the GMCs were resolved at the angular resolution of the observations (≃160 pc) and have molecular gas masses ofM(H₂)≃(0.8 − 2.0)×10⁶M_⊙. These ten clouds are characterised by gas column densities [Σ(H₂) ≃ 10 M_⊙pc⁻²] and velocity dispersions [σ_v(CO) ≃ 3–12 km s⁻¹] respectively lower and comparable to those encountered in similar GMCs in the Milky Way. They follow the relation between the gas column density and the star formation activity (Schmidt law) derived using similar data over the stellar disc of NGC 4254 and other local and Virgo cluster galaxies. With analytic calculations and tuned simulations, we show that these clouds are unstable and thus expected to dissolve on relatively short timescales (∼10–30 Myr). We show that they probably formed after the collapse of dense gas clouds in the H Igas tail stripped during the gravitational interaction that the galaxy suffered several hundreds millions of years ago. The clouds are short-lived and isolated given the low density of the surrounding intracluster medium, which cannot confine the gas expelled by stellar feedback. We discuss the implications of these results in the general context of the fate of stripped gas in hostile cluster environments. 

Context.Galaxies fly inside galaxy clusters and ram pressure by the intracluster medium (ICM) can remove a large amount of the interstellar medium (ISM) from the galaxy, and deposit the gas in the ICM. The ISM decoupled from the host galaxy leaves a long trail following the moving galaxy. Such long trails track galaxy motions and they can be detected with sensitive data in Hα. Aims.We study the Hαtail trailing NGC 4569 in the Virgo cluster. Methods.The initial discovery was made with the deep Hαimaging data with CFHT from the VESTIGE project. The follow-up spectroscopic observations were carried out withAPO/DIS,MMT/Binospec, andCFHT/SITELLE. Results.Aside from the known 80 kpc Hαtail downstream of NGC 4569, the deep Hαimaging data allow the Hαtail detected to at least 230 kpc from the galaxy. More importantly, we confirmed the Hαclumps implied from the imaging data with spectroscopic data. The Hαclumps show a smooth radial velocity gradient across ∼1300 km/s, eventually reaching the velocity of the cluster. Conclusions.For the first time, this discovery offers a view of the full deceleration process of the stripped ISM. This discovery also showcases the potential with wide-field Hαsurvey on galaxy clusters to discover intracluster optical emission-line clouds originated from cluster galaxies. These clouds provide kinematic tracers to the infall history of cluster galaxies and the turbulence in the ICM. They also serve as excellent multi-phase objects for studying the classical cloud-crushing problem and other important physical processes. 

Abstract There have been 77 TNOs discovered to be librating in the distant trans-Neptunian resonances (beyond the 2:1 resonance, at semimajor axes greater than 47.7 au) in four well-characterized surveys: the Outer Solar System Origins Survey (OSSOS) and three similar prior surveys. Here, we use the OSSOS Survey Simulator to measure their intrinsic orbital distributions using an empirical parameterized model. Because many of the resonances had only one or very few detections, j : k resonant objects were grouped by k in order to have a better basis for comparison between models and reality. We also use the Survey Simulator to constrain their absolute populations, finding that they are much larger than predicted by any published Neptune migration model to date; we also find population ratios that are inconsistent with published models, presenting a challenge for future Kuiper Belt emplacement models. The estimated population ratios between these resonances are largely consistent with scattering–sticking predictions, though further discoveries of resonant TNOs with high-precision orbits will be needed to determine whether scattering–sticking can explain the entire distant resonant population or not. 

We report the discovery of 31 new high-zquasars in the redshift range 6.6 < z < 7.8. These quasars were selected from approximately 3000 deg²of sky covered during the first 1.5 years of the Euclid Wide Survey, representing the initial results of theEuclidhigh-zquasar search. Our candidate selection employed multiple machine-learning and probabilistic techniques applied to theEuclidI_E,Y_E,J_E, andH_Eimages, supplemented by ancillaryz-band data when available. Spectroscopic follow-up observations were carried out with Keck, Magellan, and the Large Binocular Telescope (LBT). Among the new discoveries, there are 12 quasars atz ≥ 7, more than doubling the number of previously known quasars atz ≥ 7. The newly discovered quasars exhibit 21.2 < J_E < 23.2 (−25.5 < M₁₄₅₀ < −23.6), extending quasar studies to the faint end of the quasar luminosity function (QLF) atz ≳ 7. The quasar with the highest-z, EUCL J172902.75+641018.1 atz ≈ 7.77, sets the new redshift record for the most distant quasar ever reported. These discoveries demonstrateEuclid’s transformative role in high-zquasar discovery and set the stage for future follow-up studies of the early galaxies hosting quasars, supermassive black hole growth, and the intergalactic medium in the epoch of reionisation. 

The Cosmic Dawn Survey pre-launch catalogues cover an effective 10.13 deg²area with uniform deepSpitzer/IRAC data (m ∼ 25 mag, 5σ), the largest area covered to these depths at IR wavelengths. We used these data to gain new insight into the growth of stellar mass across cosmic history by characterising the evolution of the galaxy stellar mass function through 0.2 < z ≤ 6.5. The total volume (0.62 Gpc³) represents an order of magnitude increase compared to previous works that exploredz > 3 and significantly reduces cosmic variance, thus yielding strong constraints on the abundance of galaxies above the characteristic stellar mass (ℳ^★) across this ten billion year period. The evolution of the galaxy stellar mass function is generally consistent with results from the literature but now provides firm estimates of the number density where only upper limits were previously available. Contrasting the galaxy stellar mass function with the dark matter halo mass function suggests that massive galaxies (ℳ ≳ 10¹¹M_⊙) atz > 3.5 required integrated star-formation efficiencies of ℳ/(ℳ_hf_b)≳ 0.25–0.5, in excess of the commonly held view of a ‘universal peak efficiency’ from studies on the stellar-to-halo mass relation. Such increased efficiencies imply an evolving peak in the stellar-to-halo mass relation atz > 3.5 that can be maintained if feedback mechanisms from active galactic nuclei and stellar processes are ineffective at early times. In addition, a significant fraction of the most massive quiescent galaxies are observed to be in place byz ∼ 2.5–3. The apparent lack of change in their number density byz ∼ 0.2 is consistent with relatively little mass growth from mergers. Utilising the unique volume, we find evidence of an environmental dependence of the galaxy stellar mass function all the way throughz ∼ 3.5 for the first time, though a more careful characterisation of the density field is ultimately required for confirmation. 

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band H α + [NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada-French-Hawaii telescope. We use a new set of data extracted from VESTIGE to study the impact of the hostile cluster environment on the star formation process down to the scale of HII regions (∼50 pc). Here, HII regions are identified and their parameters measured using the HII PHOT code on a sample of 114 late-type galaxies spanning a wide range in morphological type (Sa-Sd, Im, BCD), stellar mass (10 6.5  ≤  M star  ≤ 10 11 M ⊙ ), and star formation activity (10 −3  ≤ SFR ≤ 10 M ⊙ yr −1 ). Owing to the exquisite average resolution of the VESTIGE data (0.65 arcsec), we detect 11302 HII regions with an H α luminosity L (H α ) ≥ 10 37 erg s −1 . We show that the typical number of HII regions in gas-stripped objects is significantly lower than in healthy late-types of similar stellar mass. We also show that in these gas-stripped galaxies the number of HII regions significantly drops outside the effective radius, suggesting that the quenching process occurs outside-in, in agreement with other multifrequency observations. These new results consistently confirm that the main mechanism responsible for the decrease of the star formation activity observed in cluster galaxies is ram pressure, allowing us to discard other milder processes such as starvation or strangulation, which are unable to reproduce the observed radially truncated profiles. 

Abstract The Cosmic Evolution Survey (COSMOS) has become a cornerstone of extragalactic astronomy. Since the last public catalog in 2015, a wealth of new imaging and spectroscopic data have been collected in the COSMOS field. This paper describes the collection, processing, and analysis of these new imaging data to produce a new reference photometric redshift catalog. Source detection and multiwavelength photometry are performed for 1.7 million sources across the 2 deg 2 of the COSMOS field, ∼966,000 of which are measured with all available broadband data using both traditional aperture photometric methods and a new profile-fitting photometric extraction tool, The Farmer , which we have developed. A detailed comparison of the two resulting photometric catalogs is presented. Photometric redshifts are computed for all sources in each catalog utilizing two independent photometric redshift codes. Finally, a comparison is made between the performance of the photometric methodologies and of the redshift codes to demonstrate an exceptional degree of self-consistency in the resulting photometric redshifts. The i < 21 sources have subpercent photometric redshift accuracy and even the faintest sources at 25 < i < 27 reach a precision of 5%. Finally, these results are discussed in the context of previous, current, and future surveys in the COSMOS field. Compared to COSMOS2015, it reaches the same photometric redshift precision at almost one magnitude deeper. Both photometric catalogs and their photometric redshift solutions and physical parameters will be made available through the usual astronomical archive systems (ESO Phase 3, IPAC-IRSA, and CDS).