- ID:
- ivo://CDS.VizieR/J/ApJ/899/13
- Title:
- GASP. XXI. Star forming rate in 54 galaxies
- Short Name:
- J/ApJ/899/13
- Date:
- 15 Mar 2022 08:27:30
- Publisher:
- CDS
- Description:
- Using MUSE observations from the GASP survey, we study 54 galaxies undergoing ram pressure stripping (RPS) and spanning a wide range in galaxy mass and host cluster mass. We use this rich sample to study how the star formation rate (SFR) in the tails of stripped gas depends on the properties of the galaxy and its host cluster. We show that the interplay between all the parameters involved is complex and that there is not a single, dominant one in shaping the observed amount of SFR. Hence, we develop a simple analytical approach to describe the mass fraction of stripped gas and the SFR in the tail, as a function of the cluster velocity dispersion, galaxy stellar mass, clustercentric distance, and speed in the intracluster medium. Our model provides a good description of the observed gas truncation radius and of the fraction of SFR observed in the stripped tails, once we take into account the fact that the star formation efficiency in the tails is a factor of ~5 lower than in the galaxy disk, in agreement with GASP ongoing HI and CO observations. Finally, we estimate the contribution of RPS to the intracluster light (ICL) and find that the average SFR in the tails of ram pressure stripped gas is ~0.22M{odot}/yr per cluster. By extrapolating this result to evaluate the contribution to the ICL at different epochs, we compute an integrated average value per cluster of ~4x109M{sun} of stars formed in the tails of RPS galaxies since z~1.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/897/89
- Title:
- 1482 Gaussian clumps in the Central Molecular Zone
- Short Name:
- J/ApJ/897/89
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We carry out a systematic study of the density structure of gas in the Central Molecular Zone (CMZ) in the Galactic center by extracting clumps from the APEX Telescope Large Area Survey of the Galaxy survey at 870{mu}m. We find that the clumps follow a scaling of m={rho}_0_r^3^, which corresponds to a characteristic density of n_H_2__=1.6x10^3^/cm^3^ ({rho}_0_=112M{sun}/pc^3^) with a variation of ~0.5dex, where we assumed a gas-to-dust mass ratio of 100. This characteristic density can be interpreted as the result of thermal pressure equilibrium between the molecular gas and the warm ambient interstellar medium. Such an equilibrium can plausibly be established since shear has approximately the same strength as self-gravity. Our findings may explain the fact that star formation in the CMZ is highly inefficient compared to the rest of the Milky Way disk. We also identify a population of clumps whose densities are two orders of magnitudes higher in the vicinity of the Sgr B2 region, which we propose are produced by collisions between the clumps of lower densities. For these collisions to occur, processes such as compressive tides probably have created the appropriate condition by assembling the clumps together.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A66
- Title:
- 6.7GHz CH_3_OH maser in G24.78+0.08
- Short Name:
- J/A+A/616/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- G24.78+0.08 is a well known high-mass star-forming region, where several molecular cores harboring OB young stellar objects are found inside a clump of size ~=1pc. This article focuses on the most prominent of these cores, A1, where an intense hypercompact (HC) HII region has been discovered by previous observations. Our aim is to determine the physical conditions and the kinematics of core A1, and study the interaction of the HII region with the parental molecular core. We combine ALMA 1.4mm high-angular resolution (~=0.2'') observations of continuum and line emission with multi-epoch Very Long Baseline Interferometry data of water 22GHz and methanol 6.7GHz masers. These observations allow us to study the gas kinematics on linear scales from 10 to 10^4^au, and to accurately map the physical conditions of the gas over core A1. The 1.4mm continuum is dominated by free-free emission from the intense HC HII region (size~=1000au) observed to the North of core A1 (region A1N). Analyzing the H30{alpha} line, we reveal a fast bipolar flow in the ionized gas, covering a range of LSR velocities (VLSR) of ~=60km/s. The amplitude of the VLSR gradient, 22km/s/mpc, is one of the highest so far observed towards HC HII regions. Water and methanol masers are distributed around the HC HII region in A1N, and the maser three-dimensional (3D) velocities clearly indicate that the ionized gas is expanding at high speed (>=200km/s) into the surrounding molecular gas. The temperature distribution (in the range 100-400K) over core A1, traced with molecular (CH_3_OCHO, ^13^CH_3_CN, ^13^CH_3_OH, and CH_3_CH_2_CN) transitions with level energy in the range 30K<=E_u_/k<=300K, reflects the distribution of shocks produced by the fast-expansion of the ionized gas of the HII region. The high-energy (550K<=E_u_/k<=800K) transitions of vibrationally excited CH_3_CN are likely radiatively pumped, and their rotational temperature can significantly differ from the kinetic temperature of the gas. Over core A1, the VLSR maps from both the 1.4mm molecular lines and the 6.7GHz methanol masers consistently show a VLSR gradient (amplitude ~=0.3km/s/mpc) directed approximately S-N. Rather than gravitationally supported rotation of a massive toroid, we interpret this velocity gradient as a relatively slow expansion of core A1.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/33
- Title:
- GOBELINS. IV. VLBA obs. of Taurus
- Short Name:
- J/ApJ/859/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new trigonometric parallaxes and proper motions of young stellar objects in the Taurus molecular cloud complex from observations collected with the Very Long Baseline Array as part of the Gould's Belt Distances Survey. We detected 26 young stellar objects and derived trigonometric parallaxes for 18 stars with an accuracy of 0.3% to a few percent. We modeled the orbits of six binaries and determined the dynamical masses of the individual components in four of these systems (V1023 Tau, T Tau S, V807 Tau, and V1000 Tau). Our results are consistent with the first trigonometric parallaxes delivered by the Gaia satellite and reveal the existence of significant depth effects. We find that the central portion of the dark cloud Lynds 1495 is located at d=129.5+/-0.3pc, while the B216 clump in the filamentary structure connected to it is at d=158.1+/-1.2pc. The closest and remotest stars in our sample are located at d=126.6+/-1.7pc and d=162.7+/-0.8pc, yielding a distance difference of about 36pc. We also provide a new distance estimate for HL Tau that was recently imaged. Finally, we compute the spatial velocity of the stars with published radial velocity and investigate the kinematic properties of the various clouds and gas structures in this region.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/73
- Title:
- GOBELINS. V. Kinematics of Perseus
- Short Name:
- J/ApJ/865/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the distance and structure of the Perseus molecular cloud by combining trigonometric parallaxes from Very Long Baseline Array (VLBA) observations, taken as part of the GOBELINS survey and Gaia Data Release 2. Based on our VLBA astrometry, we obtain a distance of 321+/-10pc for IC 348. This is fully consistent with the mean distance of 320+/-26 measured by Gaia. The VLBA observations toward NGC 1333 are insufficient to claim a successful distance measurement to this cluster. Gaia parallaxes, on the other hand, yield a mean distance of 293+/-22pc. Hence, the distance along the line of sight between the eastern and western edges of the cloud is ~30pc, which is significantly smaller than previously inferred. We use Gaia proper motions and published radial velocities to derive the spatial velocities of a selected sample of stars. The average velocity vectors with respect to the LSR are (u,v,w)=(-6.1+/-1.6, 6.8+/-1.1, -0.9+/-1.2) and (-6.4+/-1.0, 2.1+/-1.4, -2.4+/-1.0)km/s for IC 348 and NGC 1333, respectively. Finally, our analysis of the kinematics of the stars has shown that there is no clear evidence of expansion, contraction, or rotational motions within the clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A3
- Title:
- G202.3+2.5 position-position-velocity cubes
- Short Name:
- J/A+A/631/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Current theories and models attempt to explain star formation globally, from core scales to giant molecular cloud scales. A multi-scale observational characterisation of an entire molecular complex is necessary to constrain them. We investigate star formation in G202.3+2.5, a ~10x3pc sub-region of the Monoceros OB1 cloud with a complex morphology harbouring interconnected filamentary structures. We aim to connect the evolution of cores and filaments in G202.3+2.5 with the global evolution of the cloud and to identify the engines of the cloud dynamics. In this first paper, the star formation activity is evaluated by surveying the distributions of dense cores and protostars, and their evolutionary state, as characterised using both infrared observations from the Herschel and WISE telescopes and molecular line observations with the IRAM 30-m telescope. We find ongoing star formation in the whole cloud, with a local peak in star formation activity around the centre of G202.3+2.5 where a chain of massive cores (10-50M_{sun}_) forms a massive ridge (>150M_{sun}_). All evolutionary stages from starless cores to Class II protostars are found in G202.3+2.5, including a possibly starless, large column density (8x10^22^cm^-2^), and massive (52M_{sun}_) core. All the core-scale observables examined in this paper point to an enhanced star formation activity centred on the junction between the three main branches of the ramified structure of G202.3+2.5. This suggests that the increased star-formation activity results from the convergence of these branches. To further investigate the origin of this enhancement, it is now necessary to extend the analysis to larger scales, in order to examine the relationship between cores, filaments and their environment. We address these points through the analysis of the dynamics of G202.3+2.5 in a joint paper.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A90
- Title:
- Halpha emission-line stars in Canis Major
- Short Name:
- J/A+A/630/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A deep objective-prism survey for H-alpha emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Halpha emitters were detected, 353 of which are new detections. There is a strong concentration of these H-alpha emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of H-alpha emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the H-alpha emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour-colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Halpha emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350pc that surrounds a strong peak at 1185pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the H-alpha stars. We find a median distance for the OB stars of 1182pc, in excellent correspondence with the distance from the H-alpha stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/111
- Title:
- HCN, HNC, H13CN & HC3N of Galactic Center map. II.
- Short Name:
- J/ApJ/903/111
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We report a statistical analysis exploring the origin of the overall low star formation efficiency (SFE) of the Galactic central molecular zone (CMZ) and the SFE diversity among the CMZ clouds using a wide-field HCN J=4-3 map, whose optically thin critical density (~10^7^/cm^3^) is the highest among the tracers ever used in CMZ surveys. Logistic regression is performed to empirically formulate star formation probability of 195 HCN clumps, 13 of which contain star formation signatures. The explanatory parameters in the best-fit model are reduced into the virial parameter {alpha}_vir_ without significant contribution from other parameters, whereas the performance of the model without {alpha}_vir_ is no better than that using randomly generated data. The threshold {alpha}_vir_ is 6, which translates into a volume density (n_H_2__) of 10^4.6^/cm^3^ with the n_H_2__-{alpha}_vir_ correlation. The scarcity of the low-{alpha}_vir_ clumps, whose fraction to all HCN clumps is 0.1, can be considered as one of the immediate causes of the suppressed SFE. No correlation between the clump size or mass and star formation probability is found, implying that HCN J= 4-3 does not immediately trace the mass of star-forming gas above a threshold density. Meanwhile, star-forming and non-star-forming clouds are degenerate in the physical parameters of the CS J=1-0 clouds, highlighting the efficacy of the HCN J=4-3 line to probe star-forming regions in the CMZ. The timescale of the high-{alpha}_vir_ to low-{alpha}_vir_ transition is <~2Myr, which is consistent with the tidal compression and X1/X2 orbit transition models but possibly does not fit the cloud-cloud collision picture.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/167
- Title:
- High-mass outflows from the COHRS CO(3-2) survey
- Short Name:
- J/ApJ/867/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An unbiased search of molecular outflows within the region of the CO High Resolution survey has identified 157 high-mass outflows from a sample of 770 APEX Telescope Large Area Survey of the Galaxy clumps with a detection rate of 20%. The detection rate of outflows increases for clumps with higher M_clump_, L_bol_, L_bol_/M_clump_,N_H2_, and T_dust_ compared to the clumps with no outflow. The detection rates of the outflow increase from protostellar (8%) to young stellar object clump (17%) to massive star-forming clump (29%). The detection rate 26% for quiescent clump is preliminary, because the sample of quiescent clumps is small. A statistical relation between the outflow and clump masses for our sample is log(M_out_/M_{sun}_)=(-1.1+/-0.21)+(0.9+/-0.07)log(M_clump_/M_{sun}_). The detection rate of outflows and the outflow mass-loss rate show an increase with increasing M_clump_, L_bol_, N_H_2_, and T_dust_, which indicates that clumps with outflow with higher parameter values are at a more advanced evolutionary stage. The outflow mechanical force increases with increasing bolometric luminosities. No clear evidence has yet been found that higher-mass outflows have different launching conditions than low-mass outflows.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A103
- Title:
- 19 highmass SFR Herschel spectra and maps
- Short Name:
- J/A+A/625/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical conditions during high-mass star formation are poorly understood. Outflow and infall motions have been detected around massive protostellar objects, but their dependence on mass, luminosity, and age is unclear. In addition, physical conditions and molecular abundances are often estimated using simple assumptions such as spherical shape and chemical homogeneity, which may limit the accuracy of the results. We aim to characterize the dust and gas distribution and kinematics of the envelopes of high-mass protostars. In particular, we search for infall motions, abundance variations, and deviations from spherical symmetry, using Herschel data from the WISH program. We used HIFI maps of the 987GHz H_2_O 2_02_-1_11_ emission to measure the sizes and shapes of 19 high-mass protostellar envelopes. To identify infall, we used HIFI spectra of the optically thin C^18^O 9-8 and H_2_^18^O 1_11_-0_00_ lines. The high-J C^18^O line traces the warm central material and redshifted H_2_^18^O 1_11_-0_00_ absorption indicates material falling onto the warm core. We probe small-scale chemical differentiation by comparing H_2_O 752 and 987GHz spectra with those of H_2_^18^O. Our measured radii of the central part of the H_2_O 2_02_-1_11_ emission are 30-40% larger than the predictions from spherical envelope models, and axis ratios are <2, which we consider good agreement. For 11 of the 19 sources, we find a significant redshift of the H_2_^18^O 1_11_-0_00_ line relative to C^18^O 9-8. The inferred infall velocities are 0.6-3.2km/s, and estimated mass inflow rates range from 7x10^-5^ to 2x10^-2^M_{sun}_/yr. The highest mass inflow rates seem to occur toward the sources with the highest masses, and possibly the youngest ages. The other sources show either expanding motions or H_2_^18^O lines in emission. The H_2_^18^O 1_11_-0_00_ line profiles are remarkably similar to the differences between the H_2_O 2_02_-1_11_ and 2_11_-2_02_ profiles, suggesting that the H_2_^18^O line and the H_2_O 2_02_-1_11_ absorption originate just inside the radius where water evaporates from grains, typically 1000-5000au from the center. In some sources, the H_2_^18^O line is detectable in the outflow, where no C^18^O emission is seen. Together, the H_2_^18^O absorption and C^18^O emission profiles show that the water abundance around high-mass protostars has at least three levels: low in the cool outer envelope, high within the 100K radius, and very high in the outflowing gas. Thus, despite the small regions, the combination of lines presented in this work reveals systematic inflows and chemical information about the outflows.
