- ID:
- ivo://CDS.VizieR/J/ApJ/772/107
- Title:
- Giant molecular clouds in nearby galaxies
- Short Name:
- J/ApJ/772/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We resolve 182 individual giant molecular clouds (GMCs) larger than 2.5x10^5^M_{sun}_ in the inner disks of 5 large nearby spiral galaxies (NGC 2403, NGC 3031, NGC 4736, NGC 4826, and NGC 6946) to create the largest such sample of extragalactic GMCs within galaxies analogous to the Milky Way. Using a conservatively chosen sample of GMCs most likely to adhere to the virial assumption, we measure cloud sizes, velocity dispersions, and ^12^CO(J=1-0) luminosities and calculate cloud virial masses. The average conversion factor from CO flux to H_2_ mass (or X_CO_) for each galaxy is 1-2x10^20^/cm2 (K.km/s)^-1^, all within a factor of two of the Milky Way disk value (~2x10^20^/cm2(K.km/s)^-1^). We find GMCs to be generally consistent within our errors between the galaxies and with Milky Way disk GMCs; the intrinsic scatter between clouds is of order a factor of two. Consistent with previous studies in the Local Group, we find a linear relationship between cloud virial mass and CO luminosity, supporting the assumption that the clouds in this GMC sample are gravitationally bound. We do not detect a significant population of GMCs with elevated velocity dispersions for their sizes, as has been detected in the Galactic center. Though the range of metallicities probed in this study is narrow, the average conversion factors of these galaxies will serve to anchor the high metallicity end of metallicity-X_CO_ trends measured using conversion factors in resolved clouds; this has been previously possible primarily with Milky Way measurements.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/803/16
- Title:
- Giant molecular clouds in NGC4526 based on ^12^CO
- Short Name:
- J/ApJ/803/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high spatial resolution (~20pc) of ^12^CO(2-1) observations of the lenticular galaxy NGC 4526. We identify 103 resolved giant molecular clouds (GMCs) and measure their properties: size R, velocity dispersion {sigma}_v_, and luminosity L. This is the first GMC catalog of an early-type galaxy. We find that the GMC population in NGC 4526 is gravitationally bound, with a virial parameter {alpha}~1. The mass distribution, dN/dM{propto}M^-2.39+/-0.03^, is steeper than that for GMCs in the inner Milky Way, but comparable to that found in some late-type galaxies. We find no size-line width correlation for the NGC 4526 clouds, in contradiction to the expectation from Larson's relation. In general, the GMCs in NGC 4526 are more luminous, denser, and have a higher velocity dispersion than equal-size GMCs in the Milky Way and other galaxies in the Local Group. These may be due to higher interstellar radiation field than in the Milky Way disk and weaker external pressure than in the Galactic center. In addition, a kinematic measurement of cloud rotation shows that the rotation is driven by the galactic shear. For the vast majority of the clouds, the rotational energy is less than the turbulent and gravitational energy, while the four innermost clouds are unbound and will likely be torn apart by the strong shear at the galactic center. We combine our data with the archival data of other galaxies to show that the surface density {Sigma} of GMCs is not approximately constant, as previously believed, but varies by ~3 orders of magnitude. We also show that the size and velocity dispersion of the GMC population across galaxies are related to the surface density, as expected from the gravitational and pressure equilibrium, i.e., {sigma}_v_R^-1/2^{propto}{Sigma}^1/2^.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/1092
- Title:
- Giant molecular clouds (SRBY)
- Short Name:
- J/ApJ/699/1092
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The properties of Galactic molecular clouds tabulated by Solomon et al. (SRBY; 1987ApJ...319..730S) are re-examined using the Boston University-FCRAO Galactic Ring Survey of ^13^COJ=1-0 emission. These new data provide a lower opacity tracer of molecular clouds and improved angular and spectral resolution compared with previous surveys of molecular line emission along the Galactic Plane. We calculate giant molecular cloud (GMC) masses within the SRBY cloud boundaries assuming local thermodynamic equilibrium (LTE) conditions throughout the cloud and a constant H_2_ to ^13^CO abundance, while accounting for the variation of the ^12^C/^13^C with galactocentric radius.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/1425
- Title:
- Gravitational lensing analysis of Abell 1689
- Short Name:
- J/MNRAS/372/1425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived the mass distribution of galaxy cluster Abell 1689 within 0.3h^-1^_70_Mpc of the cluster centre using its strong lensing (SL) effect on 32 background galaxies, which are mapped in altogether 107 multiple images. The multiple images are based on some from the literature with modifications to both include new and exclude some of the original image systems. The cluster profile is explored further out to ~2.5h^-1^_70_Mpc with weak lensing (WL) shear measurements from the literature. The masses of ~200 cluster galaxies are measured with the Fundamental Plane (FP) in order to model accurately the small-scale mass structure in the cluster. The cluster galaxies are modelled as elliptical truncated isothermal spheres. The scalings of the truncation radii with the velocity dispersions of galaxies are assumed to match those of: (i) field galaxies; and (ii) theoretical expectations for galaxies in dense environments. The dark matter (DM) component of the cluster is described by either non-singular isothermal ellipsoids (NSIE) or elliptical versions of the universal DM profile (elliptical Navarro, Frenk & White, ENFW). To account for substructure in the DM we allow for two DM haloes.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/194
- Title:
- Group of galaxies in gravitational lens fields
- Short Name:
- J/ApJ/833/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With a large, unique spectroscopic survey in the fields of 28 galaxy-scale strong gravitational lenses, we identify groups of galaxies in the 26 adequately sampled fields. Using a group-finding algorithm, we find 210 groups with at least 5 member galaxies; the median number of members is 8. Our sample spans redshifts of 0.04<=z_grp_<=0.76 with a median of 0.31, including 174 groups with 0.1<z_grp_<0.6. The groups have radial velocity dispersions of 60<={sigma}_grp_<=1200km/s with a median of 350km/s. We also discover a supergroup in field B0712+472 at z=0.29 that consists of three main groups. We recover groups similar to ~85% of those previously reported in these fields within our redshift range of sensitivity and find 187 new groups with at least five members. The properties of our group catalog, specifically, (1) the distribution of {sigma}_grp_, (2) the fraction of all sample galaxies that are group members, and (3) the fraction of groups with significant substructure, are consistent with those for other catalogs. The distribution of group virial masses agrees well with theoretical expectations. Of the lens galaxies, 12 of 26 (46%) (B1422+231, B1600+434, B2114+022, FBQS J0951+2635, HE0435-1223, HST J14113+5211, MG0751+2716, MGJ1654+1346, PG 1115+080, Q ER 0047-2808, RXJ1131-1231, and WFI J2033-4723) are members of groups with at least five galaxies, and one more (B0712+472) belongs to an additional, visually identified group candidate. There are groups not associated with the lens that still are likely to affect the lens model; in six of 25 (24%) fields (excluding the supergroup), there is at least one massive ({sigma}_grp_>=500km/s) group or group candidate projected within 2' of the lens.
- ID:
- ivo://CDS.VizieR/J/AJ/113/483
- Title:
- Groups of Galaxies
- Short Name:
- J/AJ/113/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a friends-of-friends algorithm to identify loose groups from the northern CfA2 survey covering the region 8h<={alpha}_(1950)_<=17h and 8.5{deg}<={delta}_(1950)_<=44.5{deg}. There are 406 groups; 149 of these contains five or more members within the survey. Geometric simulations guide our choice of the selection parameters; {delta}{rho}/{rho}=80 is the limiting density contrast and V0=350km/s is the fiducial velocity linking parameter. The geometric simulations are particularly important for evaluating the impact of large-scale structure (e.g., the Great Wall) on group selection. The physical parameters of this large sample are coincident with our earlier results [126 groups in Ramella et al. (1989ApJ...344...57R)]: the median velocity dispersion in 192 (156; 229)km/s and the median blue log(M/L) is 2.38 (2.20; 2.52). The mass-to-light ratio (M/L) is in units of Msun/Lsun for an assumed Hubble constant, H0=100km/s/Mpc. The numbers in parentheses are 99% confidence limits. This group catalog provides a substantially larger sample for statistical studies than has been previously available. For example, it provides a more substantial sample for estimation of the distribution of group velocity dispersions and of the group-group correlation function. (Copyright) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/VII/256
- Title:
- Groups of Galaxies from CfA2 Redshift Survey
- Short Name:
- VII/256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains statistically homogeneous and physically well graunded groups of galaxies based on the CfA2 redshift survey (Cat. J/ApJS/121/287) in the area of space 1000km/s<=cz<=15000km/s, |bII|>=20{deg}. For identification of groups we used a modification of a friends of friends (FoF) method. Principles of friendship and definition of values of presented there free parameters described in Mahtessian (1988Afz....28..255M, 1997Ap.....40..285M). There are 1971 groups with 2 or more members, for a total of 6787 members (46.3%); 765 of the groups have 3 or more members with 4375 galaxies (28.1%). The others 8790 (56.4%) galaxies make a sample of "single" galaxies. The catalog includes group numbers, numbers of members, equatorial coordinates, Virgo-centric radial velocities, line-of-sight-velocity dispersions, integrated group luminosities, and relative quantity of false members.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/341
- Title:
- Groups of Galaxies in PPS
- Short Name:
- J/A+AS/130/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large catalog of galaxy loose groups in the Southern Galactic Hemisphere, selected from the Perseus-Pisces redshift Survey (PPS). Particular care is taken in order to obtain group samples as homogeneous as possible to previously published catalogs. Groups are identified with the adaptive Friends-of-Friends (FoF) algorithm of Huchra & Geller (1982ApJ...257..423H), with suitable normalizations V_0_=350km/s and D_0_=0.231h.Mpc. As a necessary ingredient of FoF algorithms, we obtain the galaxy luminosity function (LF) for PPS. Its Schechter parameters ({alpha}=-1.15+/-0.15, M_*_=-19.3+/-0.1) are in good agreement with similar LF estimates from samples previously used to select groups. The LF normalizations {phi}_*_=0.02h^3^/Mpc^3^ appropriate for PPS yields a density threshold {delta}n/n~180 for the adopted D_0_, apparently rather different from the desired {delta}n/n~80 used in previous studies. We then consider several other link normalizations, and briefly discuss their effect on group properties. We suggest to replace the customarily adopted {delta}n/n parametrization with the more direct D_0_ parametrization. All our catalogs contain N_G_~200 groups, significantly more than in most previous studies where group samples were obtained from galaxy data sets of comparable quality to (but smaller extent than) PPS. The group properties are rather sensitive to the adopted D_0_ and V_0_, but vary little with different redshift corrections, redshift cut-off, and galaxy LF. Loose groups in PPS nicely trace the large scale structure (LSS) in the parent galaxy sample. Physical properties of groups in PPS and in other directly comparable samples are in good agreement. There seems to be a complex interplay among LSS features, FoF grouping procedure, and group properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3461
- Title:
- Halpha maps of 3 LIRGS
- Short Name:
- J/MNRAS/465/3461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed three luminous infrared galaxy systems (LIRGS) which are pairs of interacting galaxies, with the Galaxy H{alpha} Fabry-Perot system (GH{alpha}FaS) mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory, and combined the observations with the Atacama Large Millimeter Array (ALMA) observations of these systems in CO emission to compare the physical properties of the star formation regions and the molecular gas clouds, and specifically the internal kinematics of the star forming regions. We identified 88 star forming regions in the H$\alpha$ emission data-cubes, and 27 molecular cloud complexes in the CO emission data-cubes. The surface densities of the star formation rate and the molecular gas are significantly higher in these systems than in non-interacting galaxies and the Galaxy, and are closer to the surface densities of the star formation rate and the molecular gas of extreme star forming galaxies at higher redshifts. The large values of the velocity dispersion also show the enhanced gas surface density. The HII regions are situated on the {Sigma}_SFR_-{sigma}_v_ envelope, and so are also in virial equilibrium. Since the virial parameter decreases with the surface densities of both the star formation rate and the molecular gas, we claim that the clouds presented here are gravitationally dominated rather than being in equilibrium with the external pressure.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/143
- Title:
- HCO+ and N2D+ dense cores in Perseus
- Short Name:
- J/ApJ/819/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of an HCO^+^ (3-2) and N_2_D^+^ (3-2) molecular line survey performed toward 91 dense cores in the Perseus molecular cloud using the James Clerk Maxwell Telescope, to identify the fraction of starless and protostellar cores with systematic radial motions. We quantify the HCO^+^ asymmetry using a dimensionless asymmetry parameter {delta}_v_, and identify 20 cores with significant blue or red line asymmetries in optically thick emission indicative of collapsing or expanding motions, respectively. We separately fit the HCO^+^ profiles with an analytic collapse model and determine contraction (expansion) speeds toward 22 cores. Comparing the {delta}_v_ and collapse model results, we find that {delta}_v_ is a good tracer of core contraction if the optically thin emission is aligned with the model-derived systemic velocity. The contraction speeds range from subsonic (0.03km/s) to supersonic (0.40km/s), where the supersonic contraction speeds may trace global rather than local core contraction. Most cores have contraction speeds significantly less than their free-fall speeds. Only 7 of 28 starless cores have spectra well-fit by the collapse model, which more than doubles (15 of 28) for protostellar cores. Starless cores with masses greater than the Jeans mass (M/M_J_>1) are somewhat more likely to show contraction motions. We find no trend of optically thin non-thermal line width with M/M_J_, suggesting that any undetected contraction motions are small and subsonic. Most starless cores in Perseus are either not in a state of collapse or expansion, or are in a very early stage of collapse.
