- ID:
- ivo://CDS.VizieR/J/other/ApSS/361.191
- Title:
- High-mass star forming clumps from MALT90
- Short Name:
- J/other/ApSS/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A total of 197 relatively isolated high-mass star-forming clumps were selected from the Millimeter Astronomy Legacy Team 90GHz (MALT90) survey data and their global chemical evolution investigated using four molecular lines, N_2_H^+^(1-0), HCO^+^(1-0), HCN(1-0), and HNC(1-0). The results suggest that the global averaged integrated intensity ratios I(HCO^+^)/I(HNC), I(HCN)/I(HNC), I(N_2_H^+^)/I(HCO^+^), and I(N_2_H^+^)/ I(HCN) are promising tracers for evolution of high-mass star-forming clumps. The global averaged column densities and abundances of N_2_H^+^, HCO^+^, HCN, and HNC increase as clumps evolve. The global averaged abundance ratios X(HCN)/X(HNC) could be used to trace evolution of high-mass star forming clumps, X(HCO^+^)/X(HNC) is more suitable for distinguishing high-mass star-forming clumps in prestellar (stage A) from those in protostellar (stage B) and HII/PDR region (stage C). These results suggest that the global averaged integrated intensity ratios between HCN(1-0), HNC(1-0), HCO^+^(1-0) and N_2_H^+^(1-0) are more suitable for tracing the evolution of high-mass star forming clumps. We also studied the chemical properties of the target high-mass star-forming clumps in each spiral arm of the Galaxy, and got results very different from those above. This is probably due to the relatively small sample in each spiral arm. For high-mass star-forming clumps in Sagittarius arm and Norma-Outer arm, comparing two groups located on one arm with different Galactocentric distances, the clumps near the Galactic Center appear to be younger than those far from the Galactic center, which may be due to more dense gas concentrated near the Galactic Center, and hence more massive stars being formed there.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/1766
- Title:
- High-redshift AGN feedback in SZ clusters
- Short Name:
- J/MNRAS/471/1766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of active galactic nucleus (AGN) feedback at higher redshifts (0.3<z<1.2) using Sunyaev-Zel'dovich selected samples of clusters from the South Pole Telescope and Atacama Cosmology Telescope surveys. In contrast to studies of nearby systems, we do not find a separation between cooling flow (CF) clusters and non-CF clusters based on the radio luminosity of the central radio source (cRS). This lack may be due to the increased incidence of galaxy-galaxy mergers at higher redshift that triggers AGN activity. In support of this scenario, we find evidence for evolution in the radio-luminosity function of the cRS, while the lower luminosity sources do not evolve much, the higher luminosity sources show a strong increase in the frequency of their occurrence at higher redshifts. We interpret this evolution as an increase in high-excitation radio galaxies (HERGs) in massive clusters at z>0.6, implying a transition from HERG-mode accretion to lower power low-excitation radio galaxy (LERG)-mode accretion at intermediate redshifts. Additionally, we use local radio-to-jet power scaling relations to estimate feedback power and find that half of the CF systems in our sample probably have enough heating to balance cooling. However, we postulate that the local relations are likely not well suited to predict feedback power in high-luminosity HERGs, as they are derived from samples composed mainly of lower luminosity LERGs.
- ID:
- ivo://CDS.VizieR/J/A+A/362/519
- Title:
- High redshift radio galaxies emission lines
- Short Name:
- J/A+A/362/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table gives radio and spectroscopic data for 167 radio galaxies, taken from the references given in the last column, from the WENSS, Texas and NVSS radio surveys, or determined from the electronic versions of the spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/469/207
- Title:
- High-resolution images in Cep-A HW2 region
- Short Name:
- J/A+A/469/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Due to its relatively small distance (725pc), the Cepheus A East star-forming region is an ideal laboratory to study massive star formation processes. Based on its morphology, it has been suggested that the flattened molecular gas distribution around the YSO HW2 may be a 350-AU-radius massive protostellar disk. The goal of our work is to ascertain the nature of this structure. We have employed the Plateau de Bure Interferometer to acquire (sub-)arcsecond-resolution imaging of high-density and shock tracers, such as methyl cyanide (CH3CN) and silicon monoxide (SiO), towards the HW2 position. On the 1" scale, the flattened distribution of molecular gas around HW2 appears to be due to the projected superposition, on the plane of the sky, of at least three protostellar objects, of which at least one is powering a molecular outflow at a small angle with respect to the line of sight. The presence of a protostellar disk around HW2 is not ruled out.
- ID:
- ivo://CDS.VizieR/J/AJ/154/156
- Title:
- High resolution survey of Galactic plane at 408 MHz
- Short Name:
- J/AJ/154/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interstellar medium is a complex "ecosystem" with gas constituents in the atomic, molecular and ionized states, dust, magnetic fields, and relativistic particles. The Canadian Galactic Plane Survey has imaged these constituents at multiple radio and infrared frequencies with angular resolution of the order of arcminutes. This paper presents radio continuum data at 408 MHz over the area of 52{deg}=<l=<193{deg}, -6.5{deg}=<b=<8.5{deg}, with an extension to b=21{deg} in the range of 97{deg}=<l=<120{deg}, with angular resolution 2.8'x2.8' cosec{delta}. Observations were made with the Synthesis Telescope at the Dominion Radio Astrophysical Observatory as part of the Canadian Galactic Plane Survey. The calibration of the survey using existing radio source catalogs is described. The accuracy of 408 MHz flux densities from the data is 6%. Information on large structures has been incorporated into the data using the single-antenna survey of Haslam et al. (1982A&AS...47....1H). The paper presents the data, describes how it can be accessed electronically, and gives examples of applications of the data to ISM research.
- ID:
- ivo://CDS.VizieR/J/A+AS/142/25
- Title:
- High velocity HI Southern Survey
- Short Name:
- J/A+AS/142/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new high-sensitivity HI survey of the southern sky was made south of Declination -25{deg}, at the Instituto Argentino de Radioastronomia (IAR), on a half-degree grid in galactic coordinates. A total of 50980 positions were observed. One of the goals of this survey was to search for high velocity clouds (HVCs). The HI profiles have been smoothed to a velocity resolution of 8km/s. The resulting rms noise falls in the range 0.015 to 0.020K. We have detected 6848 high velocity (HV) components.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A100
- Title:
- HII region G24.78+0.08 A1 images
- Short Name:
- J/A+A/624/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest phases of the evolution of a massive star are closely related to the developement of an HII region. Hypercompact HII regions are the most interesting in this respect because they are very young, and hence best suited to study the beginning of the expansion of the ionised gas inside the parental core. We have analysed the geometrical and physical structure of the hypercompact HII region G24.78+0.08 A1, making use of new continuum and hydrogen recombination line data (H41{alpha}, H63{alpha}, H66{alpha}, H68{alpha}) and data from the literature (H30{alpha}, H35{alpha}). We fit the continuum spectrum with a homogenous, isothermal shell of ionised gas at 10^4^K and derive the size of the HII region and the Lyman continuum luminosity of the ionising star. We also fit the recombination line spectra emitted from the same shell with a model taking into account expansion at constant speed. The best fits to the continuum and line spectra allow the derivation of the Lyman continuum luminosity of the ionising star, HII region size, geometrical thickness of the shell, and expansion velocity. Comparison between the 5cm and 7mm brightness temperature distributions demonstrates that a thin layer of ionised gas of a few 1000K at the surface of the HII region is necessary to reproduce the morphology of the continuum emission at both wavelengths. We confirm that the G24 A1 hypercompact HII region consists of a thin shell ionised by an O9.5 star. The shell is expanding at a speed comparable to the sound speed in the ionised gas. The radius of the HII region exceeds the critical value needed to trap the ionised gas by the gravitational field of the star, consistent with the observed expansion.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/117
- Title:
- HII region kinematic distances
- Short Name:
- J/ApJ/774/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We make a comprehensive study of H I absorption toward H II regions located within |l|<10{deg}. Structures in the extreme inner Galaxy are traced using the longitude-velocity space distribution of this absorption. We find significant H I absorption associated with the Near and Far 3kpc Arms, the Connecting Arm, Bania's Clump 1, and the HI Tilted Disk. We also constrain the line-of-sight distances to H II regions, by using H I absorption spectra together with the H II region velocities measured by radio recombination lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/424
- Title:
- HII regions identified with WMAPS and GLIMPSE
- Short Name:
- J/ApJ/709/424
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Wilkinson Microwave Anisotropy Probe (WMAP) maximum entropy method foreground emission map combined with previously determined distances to giant HII regions to measure the free-free flux at Earth and the free-free luminosity of the Galaxy. We find a total flux f_{nu}_=54211Jy and a flux from 88 sources of f_{nu}_=36043Jy. The bulk of the sources are at least marginally resolved, with mean radii ~60pc, electron density n_e_~9cm^-3^, and filling factor {Phi}HII~0.005 (over the Galactic gas disk). We use GLIMPSE and Midcourse Space Experiment (MSX) 8um images to show that the bulk of the free-free luminosity is associated with bubbles having radii r~5-100pc, with a mean of ~20pc. These bubbles are leaky, so that ionizing photons emitted inside the bubble escape and excite free-free emission beyond the bubble walls, producing WMAP sources that are larger than the 8um bubbles. We suggest that the WMAP sources are the counterparts of the extended low density HII regions described by Mezger (1978A&A....70..565M). The 18 most luminous WMAP sources emit half the total Galactic ionizing flux.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A127
- Title:
- HII regions synchrotron radiation
- Short Name:
- J/A+A/621/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmic rays (CRs) and magnetic fields are dynamically important components in the Galaxy, and their energy densities are comparable to that of the turbulent interstellar gas. The interaction of CRs and Galactic magnetic fields (GMF) produces synchrotron radiation clearly visible in the radio regime. Detailed measurements of synchrotron radiation averaged over the line-of-sight (LOS), so-called synchrotron emissivities, can be used as a tracer of the CR density and GMF strength. Our aim is to model the synchrotron emissivity in the Milky Way using a three-dimensional dataset instead of LOS-integrated intensity maps on the sky. Using absorbed HII regions, we measured the synchrotron emissivity over a part of the LOS through the Galaxy, changing from a two-dimensional to a three-dimensional view. Performing these measurements on a large scale is one of the new applications of the window opened by current low-frequency arrays. Using various simple axisymmetric emissivity models and a number of GMF-based emissivity models, we were able to simulate the synchrotron emissivities and compare them to the observed values in the catalog. We present a catalog of low-frequency absorption measurements of HII regions, their distances and electron temperatures, compiled from literature. These data show that the axisymmetric emissivity models are not complex enough, but the GMF-based emissivity models deliver a reasonable fit. These models suggest that the fit can be improved by either an enhanced synchrotron emissivity in the outer reaches of the Milky Way or an emissivity drop near the Galactic center. Current GMF models plus a constant CR density model cannot explain low-frequency absorption measurements, but the fits improved with slight (ad hoc) adaptations. It is clear that more detailed models are needed, but the current results are very promising.
