A Herschel and CARMA view of CO and [C II] in Hickson Compact groups

Understanding the evolution of galaxies from the starforming blue cloud to the quiescent red sequence has been revolutionized by observations taken with Herschel Space Observatory, and the onset of the era of sensitive millimeter interferometers, allowing astronomers to probe both cold dust as well as the cool interstellar medium in a large set of galaxies with unprecedented sensitivity. Recent Herschel observations of of H2-bright Hickson Compact Groups of galaxies (HCGs) has shown that [CII] may be boosted in diffuse shocked gas. CARMA CO(1-0) observations of these [CII]-bright HCGs has shown that these turbulent systems also can show suppression of SF. Here we present preliminary results from observations of HCGs with Herschel and CARMA, and their [CII] and CO(1-0) properties to discuss how shocks influence galaxy transitions and star formation.Comment: 4 pages, 3 figures, Proceedings for IAU Symposium 309, Galaxies in 3D across the Univers

Deep HI Mapping of Stephan’s Quintet and Its Neighborhood

National Key R&D Programme of China No. 2017YFA0402704National Natural Science Foundation of China (NSFC) No. 11873055The Chinese Academy of Sciences (CAS)CAS South America Center for AstronomyNSFC grant No. 11733006Grant No. 1180304412173045CMS-CSST-2021-A05Zhejiang Lab Open Research Project (No. K2022PE0AB01)Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CASNational key R&D program of China under grant No. 2018YFE0202900University Annual Scientific Research Plan of Anhui Province (No. 2022AH010013)National Key R&D Program of China for grant No. 2022YFA1605300The National Nature Science Foundation of China (NSFC) grants No. 1227305111933003Grant No. 11933003Project PID2020-114414GB-100MCIN/AEI/10.13039/ 501100011033P20_00334 financed by the Junta de AndalucíaFEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades/ Proyecto A-FQM-510-UGR20Knut and Alice Wallenberg FoundationFAST, a Chinese national mega-science facility built and operated by the National Astronomical ObservatoriesCAS and the Peopleʼs Government of Yunnan ProvinceJet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administratio

Dust grain size evolution in local galaxies: a comparison between observations and simulations

The evolution of the dust grain size distribution has been studied in recent years with great detail in cosmological hydrodynamical simulations taking into account all the channels under which dust evolves in the interstellar medium. We present a systematic analysis of the observed spectral energy distribution of a large sample of galaxies in the local Universe in order to derive not only the total dust masses but also the relative mass fraction between small and large dust grains ( D S / D L ). Simulations reproduce fairly well the observations except for the high-stellar mass regime where dust masses tend to be o v erestimated. We find that ∼45 per cent of galaxies exhibit D S / D L consistent with the expectations of simulations, while there is a subsample of massive galaxies presenting high D S / D L (log ( D S / D L ) ∼−0.5), and deviating from the prediction in simulations. For these galaxies which also have high-molecular gas mass fractions and metallicities, coagulation is not an important mechanism affecting the dust e volution. Including dif fusion, transporting large grains from dense regions to a more diffuse medium where they can be easily shattered, would explain the observed high D S / D L values in these galaxies. With this study, we reinforce the use of the small-to-large grain mass ratio to study the relative importance of the different mechanisms in the dust life cycle. Multiphase hydrodynamical simulations with detailed feedback prescriptions and more realistic subgrid models for the dense phase could help to reproduce the evolution of the dust grain size distribution traced by observations.MCIN/AEI PID2020-114414GB-100 Spanish Government AYA2017-84897-PJunta de Andalucia P2000334 A-FQM-510-UGR20FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades European Research Council (ERC) European Commission 851622HPCI System Research Project hp200041 hp210090Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) JP17H01111 19H05810 20H00180Ministry of Science and Technology, China MOST 107-2923-M-001-003-MY3 MOST 108-2112-M-001-007-MY3Academia Sinica - Taiwan AS-IA-109-M02National Basic Research Program of China 2017YFA0402704Comunidad de Madrid 2018-T1/TIC-1103

Formation of Molecular Gas in the debris of violent Galaxy Interactions

In many gravitational interactions between galaxies, gas and stars that have been torn from either or both of the precursor galaxies can collect in 'tidal tails'. Star formation begins anew in these regions to produce 'tidal dwarf galaxies', giving insight into the process of galaxy formation through the well-defined timescale of the interaction. But tracking the star formation process has proved to be difficult: the tidal dwarf galaxies with young stars showed no evidence of the molecular gas out of which new stars form. Here we report the discovery of molecular gas (carbon monoxide emission) in two tidal dwarf galaxies. In both cases, the molecular gas peaks at the same location as the maximum in atomic-hydrogen density, unlike most gas-rich galaxies. We infer from this that the molecular gas formed from the HI, rather than being torn in molecular form from the interacting galaxies. Star formation in the tidal dwarfs appears to mimic that process in normal spiral galaxies like our own.Comment: 8 pages, 3 figures, Nature in pres

A 0.6 Mpc H i structure associated with Stephan’s Quintet

This work is supported by the National Key R&D Programme of China No. 2017YFA0402704 and National Natural Science Foundation of China (NSFC) No. 11873055 and sponsored (in part) by the Chinese Academy of Sciences (CAS) through a grant to the CAS South America Center for Astronomy. C.K.X. acknowledges NSFC grant No. 11733006. C.C. acknowledges NSFC grant No. 11803044 and 12173045. N.-Y.T. is supported by the National key R&D program of China under grant no. 2018YFE0202900 and the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS. J.-S.H. acknowledges NSFC grant No. 11933003. U.L. acknowledges support from project PID2020-114414GB-100, financed by MCIN/AEI/10.13039/501100011033, from project P20_00334 financed by the Junta de Andalucia and from FEDER/Junta de Andalucía-Consejería de Transformaciòn Econòmica, Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20. F.R. acknowledges support from the Knut and Alice Wallenberg Foundation. This work made use of data from FAST, a Chinese national mega-science facility built and operated by the National Astronomical Observatories, CAS. We thank P. Jiang, L. Hou, C. Sun and other FAST operation team members for supports in the observations and data reductions, and H.-C. Feng and Y. Huang for helping with the optical spectroscopic observation of NGC 7320a. Support of the staff from the Lijiang 2.4 m telescope is acknowledged. Funding for the Lijiang 2.4 m telescope has been provided by the CAS and the People’s Government of Yunnan Province. This research has made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We dedicate this Article to the memory of Y. Gao, a coauthor of the Article who passed away recently.Data availability Observational data are available from the FAST archive (http://fast.bao. ac.cn) 1 year after data collection, following FAST data policy. The data that support the findings of this study are openly available in Science Data Bank at https://www.scidb.cn/s/jiIfee.Stephan’s Quintet (SQ, co-moving radial distance = 85 ± 6 Mpc, taken from the NASA/IPAC Extragalactic Database (NED)1) is unique among compact groups of galaxies2-12. Observations have previously shown that interactions between multiple members, including a high-speed intruder galaxy currently colliding into the intragroup medium, have probably generated tidal debris in the form of multiple gaseous and stellar filaments6,8,13, the formation of tidal dwarfs7,14,15 and intragroup-medium starbursts16, as well as widespread intergalactic shocked gas5,10,11,17. The details and timing of the interactions and collisions remain poorly understood because of their multiple nature18,19. Here we report atomic hydrogen (H i) observations in the vicinity of SQ with a smoothed sensitivity of 1σ = 4.2 × 1016 cm−2 per channel (velocity bin-width Δv = 20 km s−1; angular resolution = 4′), which are about two orders of magnitude deeper than previous observations8,13,20,21. The data show a large H i structure (with linear scale of around 0.6 Mpc) encompassing an extended source of size approximately 0.4 Mpc associated with the debris field and a curved diffuse feature of length around 0.5 Mpc attached to the south edge of the extended source. The diffuse feature was probably produced by tidal interactions in early stages of the formation of SQ (>1 Gyr ago), although it is not clear how the low-density H i gas (NH i ≲ 1018 cm−2) can survive the ionization by the intergalactic ultraviolet background on such a long time scale. Our observations require a rethinking of properties of gas in outer parts of galaxy groups and demand complex modelling of different phases of the intragroup medium in simulations of group formation.CAMS-CAS 11933003Chinese Academy of Sciences South America Center for Astronomy 11733006, 11803044, 12173045National Natural Science Foundation of China 11873055Chinese Academy of SciencesNational Key Research and Development Program of China 2017YFA0402704, 2018YFE020290

Dust properties and distribution in dwarf galaxies

We present a study of the extinction, traced by the Balmer decrement, in HII regions in the dwarf galaxies NGC 1569 and NGC 4214. We find that the large-scale extinction around the most prominent HII regions in both galaxies forms a shell in which locally the intrinsic extinction can adopt relatively high values ($A_V = 0.8 - 0.9$ mag) despite the low metallicity and thus the low overall dust content. The small-scale extinction (spatial resolution $\sim$0.3'') shows fluctuations that are most likely due to variations in the dust distribution. We compare the distribution of the extinction to that of the dust emission, traced by Spitzer emission at 8 and 24 \mi, and to the emission of cold dust at 850 \mi. We find in general a good agreement between all tracers, expect for the 850 \mi emission in NGC 4214 which is more extended than the extinction and the other emissions. Whereas in NGC 1569 the dust emission at all wavelengths is very similar, NGC 4214 shows spatial variations in the 24-to-850 \mi ratio. We furthermore compared the 24 \mi and the extinction-corrected Halpha emission from HII regions in a sample of galaxies with a wide range of metallicities and found a good correlation between both emissions, independent of metallicity. We suggest that this lack of dependence on metallicity might be due to the formation of dust shells with a relatively constant opacity, like the ones observed here, around ionizing stars.Comment: 5 pages, to appear in proceeding of IAU Symposition 255 "Low-metallicity star formation", ed. L. Hunt, S. Madden, & R. Schneider (Cambridge: CUP

Dark matter halos and scaling relations of extremely massive spiral galaxies from extended H I rotation curves

We present new and archival atomic hydrogen (H I ) observations of 15 of the most massive spiral galaxies in the local Universe ( M (* )> 10 (11) M-?). From 3D kinematic modeling of the datacubes, we derive extended HI rotation curves, and from these, we estimate masses of the dark matter halos and specific angular momenta of the discs. We confirm that massive spiral galaxies lie at the upper ends of the Tully-Fisher relation (mass vs velocity, M infinity V (4) ) and Fall relation (specific angular momentum vs mass, j infinity M (0.6) ), in both stellar and baryonic forms, with no significant deviations from single power laws. We study the connections between baryons and dark matter through the stellar (and baryon)-to-halo ratios of mass f(M) equivalent to M (*) /M-h and specific angular momentum f (j, *) equivalent to j( *) /j(h) and f( j, bar) equivalent to j(bar) /j(h). Combining our sample with others from the literature for less massive disc-dominated galaxies, we find that f(M) rises monotonically with M (*) and M-h (instead of the inverted-U shaped f(M) for spheroid-dominated galaxies), while f (j, *) and f( j, bar) are essentially constant near unity o v er four decades in mass. Our results indicate that disc galaxies constitute a self-similar population of objects closely linked to the self-similarity of their dark halos. This picture is reminiscent of early analytical models of galaxy formation wherein discs grow by relatively smooth and gradual inflow, isolated from disruptive events such as major mergers and strong active galactic nuclei feedback, in contrast to the more chaotic growth of spheroids.National Science Foundation (NSF) 1616177European Research Council (ERC) European Commission 101040751 ERC under the European Union Horizon 2020 research and innovation program 834148Brinson FoundationMCIN/AEI PID2020-114414GB-100Junta de Andalucia P20_00334 FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades A-FQM-510-UGR20 NSF/AST-171482

The role of gravitational supernovae in the Galactic evolution of the Li, Be and B isotopes

The observed Be and B relationships with metallicity clearly support the idea that both elements have a primary origin and that are produced by the same class of objects. Spallation by particles accelerated during gravitational events (SNII, SNIb/c) seems to be a likely origin. We show, in the context of a model of chemical evolution, that it is possible to solve the Li, Be and B abundance puzzle with the yields recently proposed by Ramaty et al. (1997), provided that SNII are unable to significantly accelerate helium nuclei and that different mechanisms are allowed to act simultaneously