scholarly journals CLASH-VLT: Enhancement of (O/H) in z  =  0.35 RX J2248−4431 cluster galaxies

2020 ◽  
Vol 633 ◽  
pp. A139 ◽  
Author(s):  
B. I. Ciocan ◽  
C. Maier ◽  
B. L. Ziegler ◽  
M. Verdugo
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Environmental Effects ◽  
High Mass ◽  
Intermediate Mass ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Evolution Of Galaxies ◽  
Halo Gas ◽  
Mass Field

Aims. Gas-phase metallicities offer insight into the chemical evolution of galaxies as they reflect the recycling of gas through star formation and galactic inflows and outflows. Environmental effects such as star-formation quenching mechanisms play an important role in shaping the evolution of galaxies. Clusters of galaxies at z <  0.5 are expected to be the sites where environmental effects can be clearly observed with present-day telescopes. Methods. We explored the Frontier Fields cluster RX J2248−443 at z = 0.348 with VIMOS/VLT spectroscopy from CLASH-VLT, which covers a central region corresponding to almost 2 virial radii. The fluxes of [OII] λ3727, Hβ, [OIII] λ5007, Hα and [NII] λ6584 emission lines were measured allowing the derivation of (O/H) gas metallicities, star formation rates based on extinction-corrected Hα fluxes, and contamination from active galactic nuclei. We compared our sample of cluster galaxies to a population of field galaxies at similar redshifts. Results. We use the location of galaxies in projected phase-space to distinguish between cluster and field galaxies. Both populations follow the star-forming sequence in the diagnostic diagrams, which allow the ionising sources in a galaxy to be disentangled, with only a low number of galaxies classified as Seyfert II. Both field and cluster galaxies follow the “main sequence” of star-forming galaxies, with no substantial difference observed between the two populations. In the mass–metallicity (MZ) plane, both high-mass field and cluster galaxies show comparable (O/H)s to the local SDSS MZ relation, with an offset of low-mass galaxies (log(M/M⊙) < 9.2) towards higher metallicities. While both the metallicities of “accreted” (R <  R500) and “infalling” (R >  R500) cluster members are comparable at all masses, the cluster galaxies from the “mass complete” bin (which is the intermediate mass bin in this study: 9.2 <  log(M/M⊙) < 10.2), show more enhanced metallicities than their field counterparts by a factor of 0.065 dex with a ∼1.8σ significance. The intermediate-mass field galaxies are in accordance with the expected (O/H)s from the fundamental metallicity relation, while the cluster members deviate strongly from the model predictions, namely by a factor of ∼0.12 dex. The results of this work are in accordance with studies of other clusters at z <  0.5 and favour the scenario in which the hot halo gas of low- and intermediate-mass cluster galaxies is removed due to ram pressure stripping, leading to an increase in their gas-phase metallicity.

scholarly journals Complex organic molecules in low-mass protostars on Solar System scales

2020 ◽  
Vol 639 ◽  
pp. A87 ◽  
Author(s):  
M. L. van Gelder ◽  
B. Tabone ◽  
Ł. Tychoniec ◽  
E. F. van Dishoeck ◽  
H. Beuther ◽  
...  
Keyword(s):  
Star Formation ◽  
Solar System ◽  
Gas Phase ◽  
Organic Molecules ◽  
High Mass ◽  
Local Source ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Complex Organic

Context. Complex organic molecules (COMs) are thought to form on icy dust grains in the earliest phase of star formation. The evolution of these COMs from the youngest Class 0/I protostellar phases toward the more evolved Class II phase is still not fully understood. Since planet formation seems to start early, and mature disks are too cold for characteristic COM emission lines, studying the inventory of COMs on Solar- System scales in the Class 0/I stage is relevant. Aims. Our aim is to determine the abundance ratios of oxygen-bearing COMs in Class 0 protostellar systems on scales of ~100 AU radius. We aim to compare these abundances with one another, and to the abundances of other low-mass protostars such as IRAS 16293-2422B and HH 212. Additionally, using both cold and hot COM lines, the gas-phase abundances can be tracked from a cold to a hot component, and ultimately be compared with those in ices to be measured with the James Webb Space Telescope (JWST). The abundance of deuterated methanol allows us to probe the ambient temperature during the formation of this species. Methods. ALMA Band 3 (3 mm) and Band 6 (1 mm) observations are obtained for seven Class 0 protostars in the Perseus and Serpens star-forming regions. By modeling the inner protostellar region using local thermodynamic equilibrium models, the excitation temperature and column densities are determined for several O-bearing COMs including methanol (CH3OH), acetaldehyde (CH3CHO), methyl formate (CH3OCHO), and dimethyl ether (CH3OCH3). Abundance ratios are taken with respect to CH3OH. Results. Three out of the seven of the observed sources, B1-c, B1-bS (both Perseus), and Serpens S68N (Serpens), show COM emission. No clear correlation seems to exist between the occurrence of COMs and source luminosity. The abundances of several COMs such as CH3OCHO, CH3OCH3, acetone (CH3COCH3), and ethylene glycol ((CH2OH)2) are remarkably similar for the three COM-rich sources; this similarity also extends to IRAS 16293-2422B and HH 212, even though collectively these sources originate from four different star-forming regions (i.e., Perseus, Serpens, Ophiuchus, and Orion). For other COMs like CH3CHO, ethanol (CH3CH2OH), and glycolaldehyde (CH2OHCHO), the abundances differ by up to an order of magnitude, indicating that local source conditions become important. B1-c hosts a cold (Tex ≈ 60 K), more extended component of COM emission with a column density of typically a few percent of the warm/hot (Tex ~ 200 K) central component. A D/H ratio of 1–3% is derived for B1-c, S68N, and B1-bS based on the CH2DOH/CH3OH ratio (taking into account statistical weighting) suggesting a temperature of ~15 K during the formation of methanol. This ratio is consistent with other low-mass protostars, but is lower than for high-mass star-forming regions. Conclusions. The abundance ratios of most O-bearing COMs are roughly fixed between different star-forming regions, and are presumably set at an earlier cold prestellar phase. For several COMs, local source properties become important. Future mid-infrared facilities such as JWST/MIRI will be essential for the direct observation of COM ices. Combining this with a larger sample of COM-rich sources with ALMA will allow ice and gas-phase abundances to be directly linked in order to constrain the routes that produce and maintain chemical complexity during the star formation process.

scholarly journals Morphology and star formation in IllustrisTNG: the build-up of spheroids and discs

2019 ◽  
Vol 487 (4) ◽  
pp. 5416-5440 ◽  
Author(s):  
Sandro Tacchella ◽  
Benedikt Diemer ◽  
Lars Hernquist ◽  
Shy Genel ◽  
Federico Marinacci ◽  
...  
Keyword(s):  
Star Formation ◽  
Mass Density ◽  
Stellar Mass ◽  
High Mass ◽  
Intermediate Mass ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Formation Activity ◽  
Stellar Motion ◽  
Galaxy Morphology

ABSTRACT Using the IllustrisTNG simulations, we investigate the connection between galaxy morphology and star formation in central galaxies with stellar masses in the range 109–1011.5 M⊙. We quantify galaxy morphology by a kinematical decomposition of the stellar component into a spheroidal and a disc component (spheroid-to-total ratio, S/T) and by the concentration of the stellar mass density profile (C82). S/T is correlated with stellar mass and star formation activity, while C82 correlates only with stellar mass. Overall, we find good agreement with observational estimates for both S/T and C82. Low- and high-mass galaxies are dominated by random stellar motion, while only intermediate-mass galaxies (M⋆ ≈ 1010–1010.5 M⊙) are dominated by ordered rotation. Whereas higher mass galaxies are typical spheroids with high concentrations, lower mass galaxies have low concentration, pointing to different formation channels. Although we find a correlation between S/T and star formation activity, in the TNG model galaxies do not necessarily change their morphology when they transition through the green valley or when they cease their star formation, this depending on galaxy stellar mass and morphological estimator. Instead, the morphology (S/T and C82) is generally set during the star-forming phase of galaxies. The apparent correlation between S/T and star formation arises because earlier forming galaxies had, on average, a higher S/T at a given stellar mass. Furthermore, we show that mergers drive in situ bulge formation in intermediate-mass galaxies and are responsible for the recent spheroidal mass assembly in the massive galaxies with M⋆ &gt; 1011 M⊙. In particular, these massive galaxies assemble about half of the spheroidal mass while star-forming and the other half through mergers while quiescent.

scholarly journals GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

2021 ◽  
Author(s):  
A J Rigby ◽  
N Peretto ◽  
R Adam ◽  
P Ade ◽  
M Anderson ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Sensitivity ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Mass Growth ◽  
Star Forming ◽  
Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

scholarly journals Tidal Dwarf Galaxies

1998 ◽  
Vol 11 (1) ◽  
pp. 141-144
Author(s):  
P.-A. Duc ◽  
I.F. Mirabel ◽  
E. Brinks
Keyword(s):  
Environmental Effects ◽  
Intergalactic Medium ◽  
Dwarf Galaxies ◽  
Star Forming ◽  
Evolution Of Galaxies ◽  
New Generation

The life and evolution of galaxies are dramatically affected by environmental effects. Interactions with the intergalactic medium and collisions with companions cause major perturbations in the morphology and contents of galaxies: in particular stars and gas clouds may be gravitationally pulled out from their parent galaxies during tidal encounters, forming rings, tails and bridges. This debris of collisions lies at the origin of a new generation of small galaxies, the so-called “tidal dwarf galaxies” (hereafter TDGs). Such an exotic way of forming galaxies was put forward by Schweizer (1978) and by Mirabel et al. (1992), who clearly observed the genesis of a star-forming object, out of material tidally expelled from the interacting system NGC 4038/39 (“The Antennae”). Recent studies, based on optical and HI observations, have shown that TDGs actually form a class of “recycled” objects with some properties similar to the more classical dwarf irregulars (dIrr) and blue compact dwarf galaxies (BCDs).

scholarly journals Survey of ortho-H2D+ in high-mass star-forming regions

2020 ◽  
Vol 644 ◽  
pp. A34
Author(s):  
G. Sabatini ◽  
S. Bovino ◽  
A. Giannetti ◽  
F. Wyrowski ◽  
M. A. Órdenes ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Strong Dependence ◽  
Cosmic Ray ◽  
High Mass ◽  
Clear Correlation ◽  
Mass Star ◽  
Large Sample ◽  
Star Forming ◽  
Star Forming Regions

Context. Deuteration has been suggested to be a reliable chemical clock of star-forming regions due to its strong dependence on density and temperature changes during cloud contraction. In particular, the H3+ isotopologues (e.g. ortho-H2D+) seem to act as good proxies of the evolutionary stages of the star formation process. While this has been widely explored in low-mass star-forming regions, in the high-mass counterparts only a few studies have been pursued, and the reliability of deuteration as a chemical clock remains inconclusive. Aims. We present a large sample of o-H2D+ observations in high-mass star-forming regions and discuss possible empirical correlations with relevant physical quantities to assess its role as a chronometer of star-forming regions through different evolutionary stages. Methods. APEX observations of the ground-state transition of o-H2D+ were analysed in a large sample of high-mass clumps selected from the ATLASGAL survey at different evolutionary stages. Column densities and beam-averaged abundances of o-H2D+ with respect to H2, X(o-H2D+), were obtained by modelling the spectra under the assumption of local thermodynamic equilibrium. Results. We detect 16 sources in o-H2D+ and find clear correlations between X(o-H2D+) and the clump bolometric luminosity and the dust temperature, while only a mild correlation is found with the CO-depletion factor. In addition, we see a clear correlation with the luminosity-to-mass ratio, which is known to trace the evolution of the star formation process. This would indicate that the deuterated forms of H3+ are more abundant in the very early stages of the star formation process and that deuteration is influenced by the time evolution of the clumps. In this respect, our findings would suggest that the X(o-H2D+) abundance is mainly affected by the thermal changes rather than density changes in the gas. We have employed these findings together with observations of H13CO+, DCO+, and C17O to provide an estimate of the cosmic-ray ionisation rate in a sub-sample of eight clumps based on recent analytical work. Conclusions. Our study presents the largest sample of o-H2D+ in star-forming regions to date. The results confirm that the deuteration process is strongly affected by temperature and suggests that o-H2D+ can be considered a reliable chemical clock during the star formation processes, as proved by its strong temporal dependence.

scholarly journals Spatially resolved signature of quenching in star-forming galaxies

2019 ◽  
Vol 490 (2) ◽  
pp. 2347-2366 ◽  
Author(s):  
Salvatore Quai ◽  
Lucia Pozzetti ◽  
Michele Moresco ◽  
Annalisa Citro ◽  
Andrea Cimatti ◽  
...  
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Galaxy Evolution ◽  
Spatial Information ◽  
Formation Rate ◽  
Radial Profile ◽  
Control Sample ◽  
Star Forming ◽  
Radial Profiles ◽  
Two Samples

ABSTRACT Understanding when, how, and where star formation ceased (quenching) within galaxies is still a critical subject in galaxy evolution studies. Taking advantage of the new methodology developed by Quai et al. to select recently quenched galaxies, we explored the spatial information provided by the IFU data to get critical insights on this process. In particular, we analyse 10 SDSS-IV MaNGA galaxies that show regions with low [O iii]/H α compatible with a recent quenching of the star formation. We compare the properties of these 10 galaxies with those of a control sample of 8 MaNGA galaxies with ongoing star formation in the same stellar mass, redshift, and gas-phase metallicity range. The quenching regions found are located between 0.5 and 1.1 effective radii from the centre. This result is supported by the analysis of the average radial profile of the ionization parameter, which reaches a minimum at the same radii, while the one of the star-forming sample shows an almost flat trend. These quenching regions occupy a total area between ∼ 15 and 45 per cent of our galaxies. Moreover, the average radial profile of the star formation rate surface density of our sample is lower and flatter than that of the control sample, at any radii, suggesting a systematic suppression of the star formation in the inner part of our galaxies. Finally, the radial profiles of gas-phase metallicity of the two samples have a similar slope and normalization. Our results cannot be ascribed to a difference in the intrinsic properties of the analysed galaxies, suggesting a quenching scenario more complicated than a simple inside-out quenching.

scholarly journals Multiwavelength investigation of extended green object G19.88-0.53: revealing a protocluster

2020 ◽  
Vol 497 (4) ◽  
pp. 5454-5472
Author(s):  
Namitha Issac ◽  
Anandmayee Tej ◽  
Tie Liu ◽  
Watson Varricatt ◽  
Sarita Vig ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Star Formation ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Gas Kinematics ◽  
Evolutionary Spectrum ◽  
Multiple Shock

ABSTRACT A multiwavelength analysis of star formation associated with the extended green object, G19.88-0.53 is presented in this paper. With multiple detected radio and millimetre components, G19.88-0.53 unveils as harbouring a protocluster rather than a single massive young stellar object. We detect an ionized thermal jet using the upgraded Giant Meterwave Radio Telescope, India, which is found to be associated with a massive, dense and hot ALMA 2.7 mm core driving a bipolar CO outflow. Near-infrared spectroscopy with UKIRT–UIST shows the presence of multiple shock-excited H2 lines concurrent with the nature of this region. Detailed investigation of the gas kinematics using ALMA data reveals G19.88-0.53 as an active protocluster with high-mass star-forming components spanning a wide evolutionary spectrum from hot cores in accretion phase to cores driving multiple outflows to possible UCH ii regions.

scholarly journals Slow-then-rapid quenching as traced by tentative evidence for enhanced metallicities of cluster galaxies at z ∼ 0.2 in the slow quenching phase

2019 ◽  
Vol 621 ◽  
pp. A131 ◽  
Author(s):  
C. Maier ◽  
B. L. Ziegler ◽  
C. P. Haines ◽  
G. P. Smith
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Rapid Quenching ◽  
Cluster Center ◽  
Cluster Galaxy ◽  
Local Cluster ◽  
Cluster Galaxies ◽  
Star Forming ◽  
The Galaxy ◽  
Tentative Evidence

Aims. As large-scale structures in the Universe develop with time, environmental effects become more and more important as a star formation quenching mechanism. Since the effects of environmental quenching are more pronounced in denser structures that form at later times, we seek to constrain environmental quenching processes using cluster galaxies at z <  0.3. Methods. We explored seven clusters from the Local Cluster Substructure Survey (LoCuSS) at 0.15 <  z <  0.26 with spectra of 1965 cluster members in a mass-complete sample from the ACReS (Arizona Cluster Redshift Survey) Hectospec survey covering a region that corresponds to about three virial radii for each cluster. We measured fluxes of [O II] λ 3727, Hβ, [O III] λ 5007, Hα, and [N II] λ 6584 emission lines of cluster members, enabling us to unambiguously derive O/H gas metallicities. We also measured star formation rates (SFRs) from extinction-corrected Hα fluxes. We compared our cluster galaxy sample with a field sample of 705 galaxies at similar redshifts observed with Hectospec as part of the same survey. Results. We find that star-forming cluster and field galaxies show similar median specific SFRs in a given mass bin of 1 − 3.2 × 1010 M⊙ and 3.2 − 10 × 1010 M⊙, respectively. But their O/H values are displaced, in the lower mass bin, to higher values (significance 2.4σ) at projected radii of R <  R200 compared with galaxies at larger radii and in the field. The comparison with metallicity-SFR-mass model predictions with inflowing gas indicates a slow-quenching scenario in which strangulation is initiated when galaxies pass R ∼ R200 by stopping the inflow of gas. We find tentative evidence that the metallicities of cluster members inside R200 are thereby increasing, but their SFRs are hardly affected for a period of time because these galaxies consume available disk gas. We use the observed fraction of star-forming cluster galaxies as a function of clustercentric radius compared to predictions from the Millennium simulation to constrain quenching timescales to be 1−2 Gyr, which is defined as the time between the moment the galaxy passes R200 until complete quenching of star formation. This is consistent with a slow-then-rapid quenching scenario. Slow quenching (strangulation) starts when the gas inflow is stopped when the galaxy passes R200 with a phase in which cluster galaxies are still star forming, but they show elevated metallicities tracing the ongoing quenching. This phase lasts for 1−2 Gyr, and meanwhile the galaxies travel to denser inner regions of the cluster. This is followed by a “rapid” phase, i.e., a rapid complete quenching of star formation due to the increasing ram pressure toward the cluster center that can also strip the cold gas in massive galaxies.

scholarly journals Multi-scale analysis of the Monoceros OB 1 star-forming region

2019 ◽  
Vol 631 ◽  
pp. A3 ◽  
Author(s):  
Julien Montillaud ◽  
Mika Juvela ◽  
Charlotte Vastel ◽  
Jinhua He ◽  
Tie Liu ◽  
...  
Keyword(s):  
Star Formation ◽  
High Mass ◽  
Scale Analysis ◽  
Junction Region ◽  
Star Forming ◽  
Multi Scale ◽  
Filament Dynamics ◽  
The North ◽  
Star Formation Activity ◽  
Multi Scale Analysis

Context. We started a multi-scale analysis of star formation in G202.3+2.5, an intertwined filamentary sub-region of the Monoceros OB1 molecular complex, in order to provide observational constraints on current theories and models that attempt to explain star formation globally. In the first paper (Paper I), we examined the distributions of dense cores and protostars and found enhanced star formation activity in the junction region of the filaments. Aims. In this second paper, we aim to unveil the connections between the core and filament evolutions, and between the filament dynamics and the global evolution of the cloud. Methods. We characterise the gas dynamics and energy balance in different parts of G202.3+2.5 using infrared observations from the Herschel and WISE telescopes and molecular tracers observed with the IRAM 30-m and TRAO 14-m telescopes. The velocity field of the cloud is examined and velocity-coherent structures are identified, characterised, and put in perspective with the cloud environment. Results. Two main velocity components are revealed, well separated in radial velocities in the north and merged around the location of intense N2H+ emission in the centre of G202.3+2.5 where Paper I found the peak of star formation activity. We show that the relative position of the two components along the sightline, and the velocity gradient of the N2H+ emission imply that the components have been undergoing collision for ~105 yr, although it remains unclear whether the gas moves mainly along or across the filament axes. The dense gas where N2H+ is detected is interpreted as the compressed region between the two filaments, which corresponds to a high mass inflow rate of ~1 × 10−3 M⊙ yr−1 and possibly leads to a significant increase in its star formation efficiency. We identify a protostellar source in the junction region that possibly powers two crossed intermittent outflows. We show that the H II region around the nearby cluster NCG 2264 is still expanding and its role in the collision is examined. However, we cannot rule out the idea that the collision arises mostly from the global collapse of the cloud. Conclusions. The (sub-)filament-scale observables examined in this paper reveal a collision between G202.3+2.5 sub-structures and its probable role in feeding the cores in the junction region. To shed more light on this link between core and filament evolutions, one must characterise the cloud morphology, its fragmentation, and magnetic field, all at high resolution. We consider the role of the environment in this paper, but a larger-scale study of this region is now necessary to investigate the scenario of a global cloud collapse.

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