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- ID:
- ivo://CDS.VizieR/J/A+A/592/A21
- Title:
- Are infrared dark clouds really quiescent?
- Short Name:
- J/A+A/592/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dense, cold regions where high-mass stars form are poorly characterised, yet they represent an ideal opportunity to learn more about the initial conditions of high-mass star formation (HMSF), since high-mass starless cores (HMSCs) lack the violent feedback seen at later evolutionary stages. We present continuum maps obtained from the Submillimeter Array (SMA) interferometry at 1.1mm for four infrared dark clouds (IRDCs, G28.34S, IRDC 18530, IRDC 18306, and IRDC 18308). We also present 1mm/3mm line surveys using IRAM 30m single-dish observations. Our results are: (1) At a spatial resolution of 10^4^AU, the 1.1mm SMA observations resolve each source into several fragments. The mass of each fragment is on average >10M_{sun}_, which exceeds the predicted thermal Jeans mass of the whole clump by a factor of up to 60, indicating that thermal pressure does not dominate the fragmentation process. Our measured velocity dispersions in the 30m lines imply that non-thermal motions provides the extra support against gravity in the fragments. (2) Both non-detection of high-J transitions and the hyperfine multiplet fit of N_2_H^+^(1-0), C_2_H(1-0), HCN(1-0), and H^13^CN(1-0) indicate that our sources are cold and young. However, obvious detection of SiO and the asymmetric line profile of HCO^+^(1-0) in G28.34S indicate a potential protostellar object and probable infall motion. (3) With a large number of N-bearing species, the existence of carbon rings and molecular ions, and the anti-correlated spatial distributions between N_2_H^+^/NH_2_D and CO, our large-scale high-mass clumps exhibit similar chemical features as small-scale low-mass prestellar objects. This study of a small sample of IRDCs illustrates that thermal Jeans instability alone cannot explain the fragmentation of the clump into cold (~15K), dense (>10^5^cm^-3^) cores and that these IRDCs are not completely quiescent.
- ID:
- ivo://CDS.VizieR/VIII/9
- Title:
- Argentina High-Latitude H I Survey
- Short Name:
- VIII/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This survey consists of H I 21-cm spectra covering the southern sky with absolute galactic latitude |b|>10 degrees and a declination dec<-25 degrees. The observations were made with the 30m telescope of the Instituto Argentino de Radioastronomia during 1973 to 1977 and were described in Colomb et al. (1977A&AS...29...89C). The data were obtained by keeping the telescope fixed on the meridian at the desired declination and letting the sky drift through the field. The individual spectra were obtained with a 56-channel filterbank and covering the velocity range from about -40 to +40km/s. The velocity resolution is 2km/s, and the beamwidth is 30arcmin.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/3660
- Title:
- ARGOS line list {lambda}8395-8830{AA}
- Short Name:
- J/MNRAS/428/3660
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the motivation, field locations and stellar selection for the Abundances and Radial velocity Galactic Origins Survey (ARGOS) spectroscopic survey of 28000 stars in the bulge and inner disc of the Milky Way galaxy across latitudes of b=-5{deg} to -10{deg}. The primary goal of this survey is to constrain the formation processes of the bulge and establish whether it is predominantly a merger or instability remnant. From the spectra (R=11000), we have measured radial velocities and determined stellar parameters, including metallicities and [{alpha}/Fe] ratios. Distances were estimated from the derived stellar parameters and about 14000 stars are red giants within 3.5kpc of the Galactic Centre. In this paper, we present the observations and analysis methods. Subsequent papers (III and IV) will discuss the stellar metallicity distribution and kinematics of the Galactic bulge and inner disc, and the implications for the formation of the bulge.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A49
- Title:
- ARGUS images of 6 Galactic globular clusters
- Short Name:
- J/A+A/552/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from ground based VLT/FLAMES spectroscopy in combination with HST data for six Galactic globular clusters. The aim of this work is to probe whether these massive clusters host an intermediate-mass black hole at their center using analytical Jeans models.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A91
- Title:
- ArH+ and p-H2O+ spectra towards 7 molecular clouds
- Short Name:
- J/A+A/643/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the surprises of the Herschel mission was the detection of ArH+, toward the Crab Nebula in emission and in absorption toward strong Galactic background sources. Although, these detections were limited to the first quadrant of the Galaxy, the existing data suggests that ArH+ ubiquitously and exclusively probes the diffuse atomic regions of the interstellar medium. In this study we extend the coverage of ArH+ to other parts of the Galaxy with new observations of its J=1-0 transition along seven Galactic sight lines toward bright sub-millimetre continuum sources. We aim to benchmark its efficiency as a tracer of purely atomic gas by evaluating its correlation (or lack of correlation as suggested by chemical models) with other well known atomic gas tracers like OH+ and H_2_O+ and the molecular gas tracer CH. The observations of the J=1-0 line of ArH+ near 617.5GHz were made feasible with the new, sensitive SEPIA660 receiver on the APEX 12m telescope. Further, the two sidebands of this receiver allowed us to observe the N_KaKc_=1_1,0_-1_0,1_ transitions of para-H_2_O+ at 607.227GHz simultaneously with the ArH+ line. We model the optically thin absorption spectra of the different species and subsequently derived their column densities. By analysing the steady state chemistry of OH+ and o-H_2_O+ we derive on average a cosmic-ray ionisation rate of 2.3+/-0.3x10^-16^s^-1^, toward the sightlines studied in this work. Using the derived values of the cosmic-ray ionisation rates and the observed ArH+ abundances we constrain the molecular fraction of the gas traced by ArH+ to lie below 2x10^-2^ with a median value of 8.8x10^-4^. Combined, our observations of ArH+, OH+, H_2_O+ and CH probe different regimes of the interstellar medium, from diffuse atomic to diffuse and translucent molecular clouds. Over Galactic scales, we see that the distribution of N(ArH+) is associated with that of N(H), particularly in the inner Galaxy (within 7 kpc of the Galactic center) with potentially even contributions from the warm neutral medium phase of atomic gas at larger galactocentric distances. We derive an average ortho-to-para ratio for H_2_O+ of 2.1+/-1.0, which corresponds to a nuclear spin temperature of 41K, consistent with the typical gas temperatures of diffuse clouds.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A86
- Title:
- ArH+ by collision with He
- Short Name:
- J/A+A/631/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of noble gas compounds has gained renewed interest thanks to the recent detection of ArH^+^ in the interstellar medium (ISM). The analysis of physical-chemical conditions in the regions of the ISM where ArH^+^ is observed requires accurate collisional data of ArH^+^ with He, H_2_, electrons, and H. The main goals of this work are to compute the first three-dimensional potential energy surface (PES) to study the interaction of ArH^+^ with He, analyze the influence of the isotopic effects in the rate coefficients, and evaluate the rovibrational relaxation rates. Two ab initio grids of energy were computed at the coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) level of theory using the augmented correlation consistent polarized quadruple, and quintuple zeta basis sets (aug-cc-pVQZ, and aug-cc-pV5Z) and a grid at the complete basis set limit was determined. The analytical representation of the PES was performed using the reproducing kernel Hilbert space (RKHS). The dynamics of the system was studied using the close coupling method. The differences in the rate coefficients for the isotopes ^36^ArH^+^, ^38^ArH^+^, and ^40^ArH^+^ in collision with He are negligible. However, the rotational rates for the collision of ArD+ with He cannot be estimated from those for ArH^+^+He. Comparison with previous rates for the 36ArH++He collision showed discrepancies for |{Delta}j|>2, and in the case of high initial rotational states of 36ArH+ differences were found even for |{Delta}j|=1. The rates for transitions between different vibrational states were also examined. Finally, new sets of rotational rates for ^36^ArH^+^+He and ^36^ArD^+^+He are reported.
1168. ARI Catalog of Catalogs
- ID:
- ivo://org.gavo.dc/arigfh/katkat/katkat
- Title:
- ARI Catalog of Catalogs
- Short Name:
- katkat.katkat
- Date:
- 27 Dec 2024 08:31:00
- Publisher:
- The GAVO DC team
- Description:
- The "catalog of catalogs" lists catalogs containing stellar positions for the last centuries. It also lets you access digitized table data.
1169. ARI Catalog of Catalogs
- ID:
- ivo://org.gavo.dc/arigfh/katkat/q
- Title:
- ARI Catalog of Catalogs
- Short Name:
- katkat_web
- Date:
- 27 Dec 2024 08:31:00
- Publisher:
- The GAVO DC team
- Description:
- ARI katkat is a catalog of star catalogues in the spirit of G. Teleki's catalog of star catalogs (`1989BOBeo.140..131T`_ and references in there). It contains 2573 catalogs suitable for astrometric usage, starting with Flamsteed (1835) and ending in the 1970ies. For almost all of them, there is a column description file (as PDF, and unfortunately sometimes in German) and the digitized content. .. _1989BOBeo.140..131T: http://ads.g-vo.org/abs/1989BOBeo.140..131T
1170. Ariel V All-Sky Monitor
- ID:
- ivo://nasa.heasarc/ariel5
- Title:
- Ariel V All-Sky Monitor
- Short Name:
- ARIEL5
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The All Sky Monitor was one of six X-ray instruments on the Ariel 5 satellite. The satellite was launched into a low inclination (2.8 degrees), nearly circular orbit (altitude ~520 km) on 15 October 1974. Ariel 5 was actively pointed so that objects of interest could be observed by the four instruments aligned along its spin axis. The ASM was mounted 90 degrees from the spin axis; the satellite had a spin period of 6 seconds. The ASM operated from October 18, 1974 to March 10, 1980. The ASM instrument, built by the Lab for High Energy Astrophysics at NASA- Goddard Space Flight Center, provided continuous coverage of the entire sky, except for a 20 degree band straddling the satellite's equator. The ASM was intended to act as an early detection system for transients, and to monitor the variability of bright ( > 0.2 Crab) galactic sources. The instrument consisted of a pair of X-ray pinhole cameras, each covering opposite halves of the sky, with gas-filled imaging proportional counters. Position determination of sources was accomplished through position-sensitive anode wires and satellite rotation. Each camera had a 1-cm<sup>2</sup> aperture. Overall telemetry constraints limited the duty cycle for any given source to 1 percent. With the low telemetry rate provided for this instrument (1 bit/s), temporal and spectral information were sacrificed for the sake of all-sky coverage. Hence, spectral information was limited to a single 3 - 6 keV bandpass, and temporal resolution was limited to the satellite orbital period, ~100 minutes. This is a service provided by NASA HEASARC .
