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Start Over Subject radio astronomy Content Level Research
541. Galactic CHaMP. III. ^12^CO dense clump properties
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.
542. Galactic emission at decimeter wavelengths
ID:
ivo://CDS.VizieR/J/A+A/410/847
Title:
Galactic emission at decimeter wavelengths
Short Name:
J/A+A/410/847
Date:
21 Oct 2021
Publisher:
CDS
Description:
The diffuse galactic emission maps at decimeter wavelengths (408 MHz, Haslam et al., 1982A&AS...47....1H), (1420 MHz, Reich, 1982A&AS...48..219R, Reich & Reich 1986A&AS...63..205R), (2326 MHz, Jonas et al., 1998MNRAS.297..977J) have been destriped using the method proposed by Schlegel et al., 1998ApJ...500..525S. Statistical and systematic errors have been evaluated for each map. Each map is presented in two different pixelizations: ECP (Cartesian Projection) and HEALPix. In the case of HEALPix pixelization (in which the pixel area is constant), we omitted the (constant) error maps; the statistical and systematic errors for each map are summarized in the "Table 2" section below. Synchrotron spectral index and normalization factor have been evaluated using the three destriped surveys. Some of the results in this work have been derived using the HEALPix (Gorski et al., 1999, Proceedings of the MPA/ESO Conference on Evolution of Large-Scale Structure: from Recombination to Garching, ed. A.J. Banday, R.K. Sheth, & L. Da Costa, 37).
543. Galactic HII regions
ID:
ivo://CDS.VizieR/J/A+A/397/213
Title:
Galactic HII regions
Short Name:
J/A+A/397/213
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Master Catalog collects the information from 24 previously published lists and catalogs for 1442 Galactic HII regions. For each object, the Master Catalog quotes the original fluxes and diameters as well as the available information on radio line velocities, line widths and line temperatures and the errors on these quantities. The Synthetic Catalog at 2.7GHz summarizes the basic information of flux density and angular diameter for each of these objects. The catalog can be used for detailed studies of Galactic HII regions and, by extrapolation, for investigations of HII regions up to millimetric wavelengths.
544. Galactic HII regions RRL and continuum data
ID:
ivo://CDS.VizieR/J/ApJ/738/27
Title:
Galactic HII regions RRL and continuum data
Short Name:
J/ApJ/738/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
The distribution of metals in the Galaxy provides important information about galaxy formation and evolution. HII regions are the most luminous objects in the Milky Way at mid-infrared to radio wavelengths and can be seen across the entire Galactic disk. We used the National Radio Astronomy Observatory (NRAO) Green Bank Telescope to measure radio recombination line (RRL) and continuum emission in 81 Galactic HII regions. We calculated LTE electron temperatures using these data. In thermal equilibrium metal abundances are expected to set the nebular electron temperature with high abundances producing low temperatures. Our HII region distribution covers a large range of Galactocentric radius (5-22kpc) and samples the Galactic azimuth range 330-60{deg}. Using our highest quality data (72 objects) we derived an O/H Galactocentric radial gradient of -0.0383+/-0.0074dex/kpc. Combining these data with a similar survey made with the NRAO 140 Foot telescope we get a radial gradient of -0.0446+/-0.0049dex/kpc for this larger sample of 133 nebulae.
545. Galactic H2O masers
ID:
ivo://CDS.VizieR/J/A+AS/101/153
Title:
Galactic H2O masers
Short Name:
J/A+AS/101/153
Date:
21 Oct 2021
Publisher:
CDS
Description:
The association between galactic H2O masers and IRAS sources from the Point Source Catalog (Cat. II/125) is established for 442 sources out of a list of 505 objects, which includes all the galactic H2O masers north of 30{deg}, known up to 1988. Using a multivariate statistical analysis on the four far-IR fluxes of the associated IRAS source, galactic H2O masers are reclassified into two classes: those associated to star forming regions (SFR, 52%) and those associated to late type stars (STAR, 45%). The remaining 3% cannot be included in either class. The present classification is compared with others in the literature. Distances for a large subsample of 1120 masers are derived, using the galactic rotation curve for SFR and literature data for STAR.The parameters of the H2O maser emission (e.g. integrated flux, luminosity, variability), collected in a homogeneous way in the Arcetri H2O atlas (Comoretto et al. 1990A&AS...84..179C), and those of the associated IRAS sources (e.g. flux density, luminosity, colours) are used to investigate, in a statistical way, the properties of the STAR and SFR classes. In particular, we investigate the spatial distribution of masers both in the galactic plane and perpendicular to it. We also compare the H2O and IRAS luminosities, finding a good correlation. Moreover, we find that high luminosity sources show low colour temperatures and vice versa. The spectral profile and variability are then investigated by different means. Finally, the luminosity function for each maser class is derived.
546. Galactic MCs associated with HII regions
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.
547. Galactic plane VERA survey
ID:
ivo://CDS.VizieR/J/PASJ/52/631
Title:
Galactic plane VERA survey
Short Name:
J/PASJ/52/631
Date:
21 Oct 2021
Publisher:
CDS
Description:
In order to search for new VLBI sources in the galactic plane that can be used as phase reference sources in differential VLBI, we conducted 22GHz observations of radio sources in the galactic plane using the Japanese VLBI Network (J-Net). We have observed 267 VLBI source candidates selected from existing radio surveys and have detected 93 sources at a signal-to-noise ratio larger than 5. While 42 of the 93 detected sources had already been detected with VLBI at relatively lower frequency (typically 2 to 8GHz), the remaining 51 are found to be new VLBI sources detected for the first time. These are located within |b|<=5{deg}, and have a large number of galactic maser sources around them. Thus, they are potential candidates for phase reference sources for VLBI Exploration of Radio Astrometry (VERA), which is the first VLBI array dedicated to phase-referencing VLBI astrometry aimed at measuring the parallax and proper motion of maser sources in the whole Galaxy.
548. Galactic plane VLA survey
ID:
ivo://CDS.VizieR/J/AJ/96/1655
Title:
Galactic plane VLA survey
Short Name:
J/AJ/96/1655
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a continuum VLA snapshot survey of the galactic plane in the longitude range 0{deg}<=l<=90{deg} at 1.5GHz. Observations were taken every 0.5{deg} in longitude at b=0{deg}. Most fields are complete to about 30mJy peak flux density. The positions, peak, and total flux density of 471 compact sources (<30") have been measured. A complete sample of 329 sources is defined. An excess of sources above that expected from extragalactic source counts is seen for l<40{deg} at all flux-density intervals. We find 86 compact sources that are within 2.4arcmin of a source in the recent radio recombination-line survey of Lockman (1989ApJS...71..469L) Source counts excluding these 86 sources agree with extragalactic source counts for all flux-density and longitude intervals. there may only be a small number of galactic objects present in this survey that remain unidentified as such.
549. Galactic radio compact HII regions at 1.4GHz
ID:
ivo://CDS.VizieR/J/AJ/130/156
Title:
Galactic radio compact HII regions at 1.4GHz
Short Name:
J/AJ/130/156
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use a new Very Large Array Galactic plane catalog at 1.4GHz (Cat. <J/AJ/130/586>) covering the first and second Galactic quadrants (340{deg}<=l<=120{deg}, |b|<=0.8{deg} with |b|<=1.8{deg} for 350{deg}<=l<=40{deg} and |b|<=2.5{deg} for 100{deg}<=l<=105{deg}) in conjunction with the MSX6C (Cat. <V/114>) Galactic plane mid-infrared catalog to supplement and better understand our 5GHz catalog (Cat. <J/ApJS/91/347>).
550. Galactic rotation curve from selected maser
ID:
ivo://CDS.VizieR/J/PAZh/37/281
Title:
Galactic rotation curve from selected maser
Short Name:
J/PAZh/37/281
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on currently available observations of 28 maser sources in 25 star-forming regions with measured trigonometric parallaxes, proper motions, and radial velocities, we have constructed the rotation curve of the Galaxy. Taking different distances to the Galactic center R_0_, we have estimated the peculiar velocity of the Sun, the angular velocity of Galactic rotation, and its three derivatives.