- ID:
- ivo://CDS.VizieR/J/A+A/643/A61
- Title:
- Prestellar cores H2D+ and N2H+ maps
- Short Name:
- J/A+A/643/A61
- Date:
- 07 Mar 2022 07:18:04
- Publisher:
- CDS
- Description:
- The study of prestellar cores is critical as they set the initial conditions in star formation and determine the final mass of the stellar object. To date, several hypotheses are describing their gravitational collapse. Deriving the dynamical model that fits both the observed dust and the gas emission from such cores is therefore of great importance. We perform detailed line analysis and modelling of H_2_D^+^ 1_10_-1_11_ and N_2_H^+^ 4-3 emission at 372GHz, using 2'x2' maps (JCMT).Our goal is to test the most prominent dynamical models by comparing the modelled gas kinematics and spatial distribution (H_2_D^+^ and N_2_H^+^) with observations towards four prestellar (L1544, L183, L694-2, L1517B) and one protostellar core (L1521f). We fit the line profiles at all offsets showing emission using single Gaussian distributions. We investigate how the line parameters (V_LSR_, FWHM and T_A_*) change with offset, to examine the velocity field, the degree of non-thermal contributions to the line broadening, and the distribution of the material in these cores. To assess the thermal broadening, we derive the average gas kinetic temperature towards all cores using the non-LTE radiative transfer code RADEX. We perform a more detailed non-LTEradiative transfer modelling using RATRAN, where we compare the predicted spatial distribution and line profiles of H_2_D^+^ and N_2_H^+^ with observations towards all cores. To do so, we adopt the physical structure for each core predicted by three different dynamical models taken from literature: Quasi-Equilibrium Bonnor-Ebert Sphere (QE-BES), Singular Isothermal Sphere (SIS), and Larson-Penston (LP) flow. In addition, we compare these results to those of a static sphere, whose density and temperature profiles are based on the observed dust continuum. Lastly, we constrain the abundance profiles of H_2_D^+^ and N_2_H^+^ towards each core. We find that variable non-thermal contributions (variations by a factor of 2.5) are required to explain the observed line width of both H_2_D^+^ and N_2_H^+^, while the non-thermal contributions are found to be 50% higher for N_2_H^+^. The RADEX modelling results in average core column densities of ~9x10^12^cm^-2^ for H_2_D+and N_2_H^+^. The LP flow seems to be the dynamical model that can reproduce the observed spatial distribution and line profiles of H_2_D^+^ on a global scale of prestellar cores, while the SIS model systematically and significantly overestimates the width of the line profiles and underestimates the line peak intensity. We find similar abundance profiles for the prestellar cores and the protostellar core. The typical abundances of H_2_D^+^ vary between 10^-9^-10^-10^ for the inner 5000au, and drop by about an order of magnitude for the outer regions of the core (2x10^-10^-6x10^-11^). In addition, a higher N_2_H^+^ abundance by about a factor of 4 compared to H_2_D^+^ is found towards the two cores with detected emission. The presence ofN_2_H^+^ 4-3 towards the protostellar core and towards one of the prestellar cores reflects the increasing densities as the core evolves. Our analysis provides an updated picture of the physical structure of prestellar cores. Although the dynamical models account for mass differences by up to a factor of 7, the velocity structure drives the shape of the line profiles, allowing for a robust comparison between the models. We find that the SIS model can be cleary excluded in explaining the gas emission towards the cores,but a larger sample is required to differentiate clearly between the LP flow, the QE-BES and the static models. All models of collapse underestimate the intensity of the gas emission by up to several factors towards the only protostellar core in our sample, indicating that different dynamics take place in different evolutionary core stages. If the LP model is confirmed towards a larger sample of prestellarcores, it would indicate that they may form by compression or accretion of gas from larger scales. If the QE-BES model is confirmed, it means that quasi hydrostatic cores can exist within turbulent ISM.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/441/307
- Title:
- Proper motions and brightness of Cas A
- Short Name:
- J/ApJ/441/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a multiple-epoch radio study of secular changes in the SNR Cassiopeia A are reported and used to construct a model for the dynamical evolution of diffuse and clumpy ejecta components in the remnant. To quantify the current dynamical status of various ejecta components, the proper motions and brightness evolution of a sample of 304 compact radio features have been accurately determined from high-quality interferometric observations of the remnant at lambda=6 and 20cm, spanning a total time baseline of 12yr. A simple model of homologous expansion does not provide a good fit to the measured proper motions of the radio knots. We find that a single estimate of the ejecta expansion age is not appropriate, as the expansion derived from compact features varies azimuthally and radially in the remnant and differs for subsets of knots segregated by brightness. We verify that the bulk of the radio-emitting plasma in Cas A has indeed been significantly decelerated by the current epoch; bulk expansion ages of 2.5-4 times the actual age of the remnant are measured . Based on these dynamical data, and information on the kinematics of the fast moving optical knots. we synthesize a model that directly relates the dynamics of ejecta components in Cas A to various radiative processes. This model is based on the premise that the emission from Cas A, at a variety of wavelengths, is deceleration-powered. If ejecta components are distributed over a range of internal densities, a sequential "turning-on" of components, in order of increasing density, should be observed. A model for the current emission distribution in Cas A, at radio, X-ray, and optical wavelengths, is outlined in terms of deceleration considerations.
- ID:
- ivo://CDS.VizieR/J/A+A/341/L79
- Title:
- Proper motions of faint ROSAT WTT stars
- Short Name:
- J/A+A/341/L79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present proper motions of 59 stars of the ROSAT All-Sky Survey (RASS) located in direction of the Chamaeleon star forming region (SFR) in the magnitude range B=5.1-17mag. Proper motions of the fainter stars were newly derived utilizing survey Schmidt plates from the GSC~II plate archive and from a set of special plates taken with the ESO Schmidt telescope. The vector point diagram (VPD) indicates that the certified weak emission-line T Tauri (WTT) stars cluster away from the region occupied by the brighter pre-main-sequence stars (PMS) in Cha I. The distance to this new association is estimated at ~100pc, sensibly smaller than the 150pc generally assumed for the SFR. This yields an upper limit of 2km/s for the velocity dispersion of this new kinematic group. The de-reddened CM diagram of the group members suggest the WTT stars are still PMS objects, but older (3-30Myr) and less massive than previous determinations. These revised age estimates, the newly derived group peculiar velocity, and current distance estimates to the Cha~I/II/III complex would favour in-situ formation against that predicted by high velocity cloud models. Finally, based on a redetermination of the peculiar motions of stars and gas, we speculate that the whole SFR originated from the local Orion spur as a result of more classical mechanisms like interactions with the spiral arms.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/159
- Title:
- Properties of 10 galaxies with Chandra
- Short Name:
- J/ApJ/899/159
- Date:
- 11 Mar 2022 14:27:52
- Publisher:
- CDS
- Description:
- We present an archival analysis of Chandra X-ray observations for 12 nearby early-type galaxies hosting radio sources with radio power >1023W/Hz at 1.4GHz, similar to the radio power of the radio source in NGC4261. Previously, in a similar analysis of eight nearby X-ray and optically bright elliptical galaxies, Werner et al. found that NGC4261 exhibited unusually low central gas entropy compared to the full sample. In the central 0.3kpc of NGC4261, the ratio of cooling time to freefall time (tcool/tff) is less than 10, indicating that cold clouds may be precipitating out of the hot ambient medium and providing fuel for accretion in the central region. NGC4261 also hosts the most powerful radio source in the original sample. Because NGC4261 may represent an important phase during which powerful feedback from a central active galactic nucleus (AGN) is fueled by multiphase condensation in the central kiloparsec, we searched the Chandra archive for analogs to NGC4261. We present entropy profiles of those galaxies, as well as profiles of tcool/tff. We find that one of them, IC4296, exhibits properties similar to NGC4261, including the presence of only single-phase gas outside of r~2kpc and a similar central velocity dispersion. We compare the properties of NGC4261 and IC4296 to hydrodynamic simulations of AGN feedback fueled by precipitation. Over the course of those simulations, the single-phase galaxy has an entropy gradient that remains similar to the entropy profiles inferred from our observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/2163
- Title:
- Properties of galaxy group sample
- Short Name:
- J/MNRAS/497/2163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our understanding of how active galactic nucleus feedback operates in galaxy clusters has improved in recent years owing to large efforts in multiwavelength observations and hydrodynamical simulations. However, it is much less clear how feedback operates in galaxy groups, which have shallower gravitational potentials. In this work, using very deep Very Large Array and new MeerKAT observations from the MIGHTEE survey, we compiled a sample of 247 X-ray selected galaxy groups detected in the COSMOS field. We have studied the relation between the X-ray emission of the intra-group medium and the 1.4GHz radio emission of the central radio galaxy. For comparison, we have also built a control sample of 142 galaxy clusters using ROSAT and NVSS data. We find that clusters and groups follow the same correlation between X-ray and radio emission. Large radio galaxies hosted in the centres of groups and merging clusters increase the scatter of the distribution. Using statistical tests and Monte Carlo simulations, we show that the correlation is not dominated by biases or selection effects. We also find that galaxy groups are more likely than clusters to host large radio galaxies, perhaps owing to the lower ambient gas density or a more efficient accretion mode. In these groups, radiative cooling of the intra-cluster medium could be less suppressed by active galactic nucleus heating. We conclude that the feedback processes that operate in galaxy clusters are also effective in groups.
- ID:
- ivo://CDS.VizieR/J/AJ/144/129
- Title:
- Properties of 83 known stellar SiO maser sources
- Short Name:
- J/AJ/144/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out simultaneous observations of four maser lines, SiO v=1,2, ^29^SiO v=0,J=1-0, and H_2_O 6_16_-5_23_, toward 83 known SiO maser sources without H_2_O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H_2_O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H_2_O maser emission without SiO maser emission was detected from one source. Therefore, H_2_O maser emission was newly detected from 15 sources. SiO maser emission without H_2_O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H_2_O maser emission detected. SiO v=2 maser emission was detected from nine sources without v=1 maser detection. The SiO v=2 maser sources without the v=1 maser detections need to be investigated, with a large number of v=2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H_2_O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H_2_O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H_2_O masers are discussed in IRAS two-color diagrams.
- ID:
- ivo://CDS.VizieR/J/A+A/368/1006
- Title:
- Properties of OH/IR stars with IRAS LRS spectra
- Short Name:
- J/A+A/368/1006
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table contains the selected from the literature sample of 1065 OH maser sources with IRAS identification and LRS spectra. The most important physical quantities of these sources are assembled and the list of related references together with the abbreviations used is attached.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A206
- Title:
- Propynethial (HCCCHS) submm spectroscopy
- Short Name:
- J/A+A/642/A206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The majority of sulfur-containing molecules detected in the interstellar medium (ISM) are analogs of oxygen-containing compounds. Propynal was detected in the ISM in 1988, hence propynethial, its sulfur derivative, is a good target for an ISM search. Our aim is to measure the rotational spectrum of propynethial and use those measurements to search for this species in the ISM. To date, measurements of the rotational spectra of propynethial have been limited to a small number or transitions below 52GHz. The extrapolation of the prediction to lines in the milimeter-wave domain is inaccurate and does not provide data to permit an unambiguous detection. The rotational spectrum was re-investigated up to 630GHz. Using the new prediction lines of propynethial, as well as the related propynal, a variety of astronomical sources were searched, including star-forming regions and dark clouds. A total of 3288 transitions were newly assigned and fit together with those from previous studies, reaching quantum numbers up to J=107 and K_a_=24. Watson's symmetric top Hamiltonian in the I^r^ representation was used for the analysis, because the molecule is very close to the prolate limit. The search for propynethial resulted in a non-detection; upper limits to the column density were derived in each source.
- ID:
- ivo://CDS.VizieR/J/AJ/162/21
- Title:
- PS1 photometry of 2863 ICRF3 quasars
- Short Name:
- J/AJ/162/21
- Date:
- 14 Mar 2022 06:53:33
- Publisher:
- CDS
- Description:
- We make use of individual (epoch) detection data from the Pan-STARRS "3{pi}" survey for 2863 optical ICRF3 counterparts in the five wavelength bands g, r, i, z, and y, published as part of the Data Release 2. A dedicated method based on the Functional Principal Component Analysis is developed for these sparse and irregularly sampled data. With certain regularization and normalization constraints, it allows us to obtain uniform and compatible estimates of the variability amplitudes and average magnitudes between the passbands and objects. We find that the starting assumption of affinity of the light curves for a given object at different wavelengths is violated for several percent of the sample. The distributions of rms variability amplitudes are strongly skewed toward small values, peaking at ~0.1mag with tails stretching to 2mag. Statistically, the lowest variability is found for the r band and the largest for the reddest y band. A small "brighter-redder" effect is present, with amplitudes in y greater than amplitudes in g in 57% of the sample. The variability versus redshift dependence shows a strong decline with z toward redshift 3, which we interpret as the time dilation of the dominant time frequencies. The colors of radio-loud ICRF3 quasars are correlated with redshift in a complicated, wavy pattern governed by the emergence of brightest emission lines within the five passbands.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A148
- Title:
- PSZ2 cluster candidates. II.
- Short Name:
- J/A+A/631/A148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second legacy catalog of Planck Sunyaev-Zeldovich (SZ) sources, hereafter PSZ2, provides the largest galaxy cluster sample selected by means of the SZ signature of the clusters in a full sky survey. In order to fully characterize this PSZ2 sample for cosmological studies, all the members should be validated and the physical properties of the clusters, including mass and redshift, should be derived. However, at the time of its publication, roughly 21% of the 1653 PSZ2 members had no known counterpart at other wavelengths. Here, we present the second and last year of observations of our optical follow-up program 128-MULTIPLE-16/15B (hereafter LP15), which has been developed with the aim of validating all the unidentified PSZ2 sources in the northern sky with declinations higher than -15{deg} that have no correspondence in the first Planck catalog PSZ1. The description of the program and the first year of observations have been presented previously. The LP15 program was awarded 44 observing nights that were spread over two years with the Isaac Newton Telescope (INT), the Telescopio Nazionale Galileo (TNG), and the Gran Telescopio Canarias (GTC), all at Roque de los Muchachos Observatory (La Palma). Following the same method as described previously, we performed deep optical imaging for more than 200 sources with the INT and spectroscopy for almost 100 sources with the TNG and GTC at the end of the LP15 program. We adopted robust confirmation criteria based on velocity dispersion and richness estimates for the final classification of the new galaxy clusters as the optical counterparts of the PSZ2 detections. Here, we present the observations of the second year of LP15, as well as the final results of the program. The full LP15 sample comprises 190 previously unidentified PSZ2 sources. Of these, 106 objects were studied before, while the remaining sample (except for 6 candidates) has been completed in the second year and is discussed here. In addition to the LP15 sample, we here study 42 additional PSZ2 objects that were originally validated as real clusters because they matched a WISE or PSZ1 counterpart, but they had no measured spectroscopic redshift. In total, we confirm the optical counterparts for 81 PSZ2 sources after the full LP15 program, 55 of them with new spectroscopic information. Forty of these 81 clusters are presented in this paper. After the LP15 observational program the purity of the PSZ2 catalog has increased from 76.7% originally to 86.2%. In addition, we study the possible reasons for false detection, and we report a clear correlation between the number of unconfirmed sources and galactic thermal dust emission.
