- ID:
- ivo://CDS.VizieR/J/ApJ/831/67
- Title:
- Galactic CHaMP. III. ^12^CO dense clump properties
- Short Name:
- J/ApJ/831/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the second complete molecular line data release from the Census of High- and Medium-mass Protostars (CHaMP), a large-scale, unbiased, uniform mapping survey at sub-parsec resolution, of millimeter-wave line emission from 303 massive, dense molecular clumps in the Milky Way. This release is for all ^12^CO J=1->0 emission associated with the dense gas, the first from Phase II of the survey, which includes ^12^CO, ^13^CO, and C^18^O. The observed clump emission traced by both ^12^CO and HCO^+^ (from Phase I) shows very similar morphology, indicating that, for dense molecular clouds and complexes of all sizes, parsec-scale clumps contain {Xi}~75% of the mass, while only 25% of the mass lies in extended (>~10pc) or "low density" components in these same areas. The mass fraction of all gas above a density of 10^9^m^-3^ is {xi}_9_>~50%. This suggests that parsec-scale clumps may be the basic building blocks of the molecular interstellar medium, rather than the standard giant molecular cloud (GMC) concept. Using ^12^CO emission, we derive physical properties of these clumps in their entirety, and compare them to properties from HCO^+^, tracing their denser interiors. We compare the standard X-factor converting I_^12^CO_ to N_H2_ with alternative conversions, and show that only the latter give whole-clump properties that are physically consistent with those of their interiors. We infer that the clump population is systematically closer to virial equilibrium than when considering only their interiors, with perhaps half being long-lived (10s of Myr), pressure-confined entities that only terminally engage in vigorous massive star formation, supporting other evidence along these lines that was previously published.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/831/73
- Title:
- Galactic MCs associated with HII regions
- Short Name:
- J/ApJ/831/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relations between star formation and properties of molecular clouds (MCs) are studied based on a sample of star-forming regions in the Galactic Plane. Sources were selected by having radio recombination lines to provide identification of associated MCs and dense clumps. Radio continuum emission and mid-infrared emission were used to determine star formation rates (SFRs), while ^13^CO and submillimeter dust continuum emission were used to obtain the masses of molecular and dense gas, respectively. We test whether total molecular gas or dense gas provides the best predictor of SFR. We also test two specific theoretical models, one relying on the molecular mass divided by the free-fall time, the other using the free-fall time divided by the crossing time. Neither is supported by the data. The data are also compared to those from nearby star-forming regions and extragalactic data. The star formation "efficiency," defined as SFR divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all of the molecular gas.
- ID:
- ivo://CDS.VizieR/J/MNRAS/467/3140
- Title:
- Galaxies angular momentum evolution
- Short Name:
- J/MNRAS/467/3140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a MUSE (Multi-Unit Spectroscopic Explorer) and KMOS (K-band Multi-Object Spectrograph) dynamical study 405 star-forming galaxies at redshift z=0.28-1.65 (median redshift <z>=0.84). Our sample is representative of the star-forming 'main sequence', with star formation rates of SFR=0.1-30M_{sun}_/yr and stellar masses M*=10^8^-10^11^M_{sun}_. For 49+/-4 per cent of our sample, the dynamics suggest rotational support, 24+/-3 per cent are unresolved systems and 5+/-2 per cent appear to be early-stage major mergers with components on 8-30kpc scales. The remaining 22+/-5 per cent appear to be dynamically complex, irregular (or face-on systems). For galaxies whose dynamics suggest rotational support, we derive inclination-corrected rotational velocities and show that these systems lie on a similar scaling between stellar mass and specific angular momentum as local spirals with j*=J/M*{prop.to}M*^2/3^ but with a redshift evolution that scales as j*{prop.to}M*^2/3^(1+z)^-1^. We also identify a correlation between specific angular momentum and disc stability such that galaxies with the highest specific angular momentum (log(j*/M*^2/3^)>2.5) are the most stable, with Toomre Q=1.10+/-0.18, compared to Q=0.53+/-0.22 for galaxies with log(j*/M*^2/3^)<2.5. At a fixed mass, the Hubble Space Telescope morphologies of galaxies with the highest specific angular momentum resemble spiral galaxies, whilst those with low specific angular momentum are morphologically complex and dominated by several bright star-forming regions. This suggests that angular momentum plays a major role in defining the stability of gas discs: at z~1, massive galaxies that have discs with low specific angular momentum are globally unstable, clumpy and turbulent systems. In contrast, galaxies with high specific angular momentum have evolved into stable discs with spiral structure where star formation is a local (rather than global) process.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2018
- Title:
- Galaxies with large velocity dispersions
- Short Name:
- J/AJ/131/2018
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the results of a search for galaxies with large (350>=km/s) velocity dispersions. The largest systems we have found appear to be the extremes of the early-type galaxy population: compared to other galaxies with similar luminosities, they have the largest velocity dispersions and the smallest sizes.
- ID:
- ivo://CDS.VizieR/J/ApJS/246/2
- Title:
- Galaxy cluster cat. from SDSS-DR13 (GalWCat19)
- Short Name:
- J/ApJS/246/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Utilizing the SDSS-DR13 spectroscopic data set, we create a new publicly available catalog of 1800 galaxy clusters (GalWeight cluster catalog, GalWCat19) and a corresponding catalog of 34,471 identified member galaxies. The clusters are identified from overdensities in redshift phase space. The GalWeight technique introduced by Abdullah+ (2018ApJ...861...22A) is then applied to identify cluster members. The completeness of the cluster catalog (GalWCat19) and the procedure followed to determine cluster mass are tested on the Bolshoi N-body simulations. The 1800 GalWCat19 clusters range in redshift between 0.01 and 0.2 and have masses in the range of (0.4-14)x10^14^h^-1^M_{sun}_. The cluster catalog provides a large number of cluster parameters, including sky position, redshift, membership, velocity dispersion, and mass at overdensities {Delta}=500, 200, 100, and 5.5. The 34471 member galaxies are identified within the radius at which the density is 200 times the critical density of the universe. The galaxy catalog provides the coordinates of each galaxy and the ID of the cluster that the galaxy belongs to. The cluster velocity dispersion scales with mass as log({sigma}_200_)=log(946+/-52km/s)+ (0.349+/-0.142)log[h(z)M_200_/10^1 5^M_{sun}], with a scatter of {delta}log{sigma}=0.06+/-0.04.
- ID:
- ivo://CDS.VizieR/J/A+A/338/813
- Title:
- Galaxy clusters {sigma}-T relationship
- Short Name:
- J/A+A/338/813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a sample of 149 galaxy clusters for which both the X-ray determined temperature T of the intracluster gas and the optical measured velocity dispersion {sigma} of the cluster galaxies have been available.
- ID:
- ivo://CDS.VizieR/J/ApJ/552/427
- Title:
- Galaxy groups a intermediate redshifts
- Short Name:
- J/ApJ/552/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy groups likely to be virialized are identified within the CNOC2, (Yee et al., 2000, Cat. <J/ApJS/129/475>) intermediate-redshift galaxy survey. The resulting groups have a median velocity dispersion, {sigma}1=~200km/s. The virial mass-to-light ratios, using k-corrected and evolution-compensated luminosities, have medians in the range of 150-250h M_{suns}_/L_{sun}_, depending on group definition details. The number-velocity dispersion relation at {sigma}1>~200km/s is in agreement with the low-mass extrapolation of the cluster-normalized Press-Schechter model. Lower velocity dispersion groups are deficient relative to the Press-Schechter model. The two-point group-group autocorrelation function has r0=6.8+/-0.3h^-1^Mpc, which is much larger than the correlations of individual galaxies, but about as expected from biased clustering. The mean number density of galaxies around group centers falls nearly as a power law with r^-2.5^ and has no well-defined core. The projected velocity dispersion of galaxies around group centers is either flat or slowly rising outward. The combination of a steeper than isothermal density profile and the outward rising velocity dispersion implies that the mass-to-light ratio of groups rises with radius if the velocity ellipsoid is isotropic but could be nearly constant if the galaxy orbits are nearly circular. Such strong tangential anisotropy is not supported by other evidence. Although the implication of a rising M/L must be viewed with caution, it could naturally arise through dynamical friction acting on the galaxies in a background of "classical" collisionless dark matter.
- ID:
- ivo://CDS.VizieR/J/ApJS/167/1
- Title:
- Galaxy groups and clusters from SDSS
- Short Name:
- J/ApJS/167/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify galaxy groups and clusters in volume-limited samples of the Sloan Digital Sky Survey (SDSS) redshift survey, using a redshift-space friends-of-friends algorithm. We optimize the friends-of-friends linking lengths to recover galaxy systems that occupy the same dark matter halos, using a set of mock catalogs created by populating halos of N-body simulations with galaxies. Extensive tests with these mock catalogs show that no combination of perpendicular and line-of-sight linking lengths is able to yield groups and clusters that simultaneously recover the true halo multiplicity function, projected size distribution, and velocity dispersion. We adopt a linking length combination that yields, for galaxy groups with 10 or more members: a group multiplicity function that is unbiased with respect to the true halo multiplicity function; an unbiased median relation between the multiplicities of groups and their associated halos; a spurious group fraction of less than ~1%; a halo completeness of more than 97%; the correct projected size distribution as a function of multiplicity; and a velocity dispersion distribution that is ~20% too low at all multiplicities. These results hold over a range of mock catalogs that use different input recipes of populating halos with galaxies. We apply our group-finding algorithm to the SDSS data and obtain three group and cluster catalogs for three volume-limited samples that cover 3495.1deg^2^ on the sky, go out to redshifts of 0.1, 0.068, and 0.045, and contain 57138, 37820, and 18895 galaxies, respectively. We correct for incompleteness caused by fiber collisions and survey edges and obtain measurements of the group multiplicity function, with errors calculated from realistic mock catalogs. These multiplicity function measurements provide a key constraint on the relation between galaxy populations and dark matter halos.
- ID:
- ivo://CDS.VizieR/J/ApJ/625/6
- Title:
- Galaxy groups in the DEEP2 Galaxy Redshift Survey
- Short Name:
- J/ApJ/625/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7<=z<=1.4, over 1{deg}^2^ on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350km/s. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z~1.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A61
- Title:
- Galaxy groups in the 2M++
- Short Name:
- J/A+A/578/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide the galaxy group sample used as tracers of the large scale structure in the work to study the compact group environment.
