Atomic and molecular cloud formation is a dynamical process. However, kinematic signatures of these processes are still observationally poorly constrained. Identify and characterize the cloud formation signatures in atomic and molecular gas. Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employ spectral line imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in ^13^CO in the 1-0 and 3-2 transitions. The analysis comprises investigations of the kinematic properties of the different tracers, estimates of the mass flow rates, velocity structure functions, a Histogram of Oriented Gradients (HOG) study as well as comparisons to simulations. The central IRDC is embedded in a more diffuse envelope of cold neutral medium (CNM) traced by HI self-absorption (HISA) and molecular gas. The spectral line data as well as the HOG and structure function analysis indicate a possible kinematic decoupling of the HI from the other gas compounds. Spectral analysis and position-velocity diagrams reveal two velocity components that converge at the position of the IRDC. Estimated mass flow rates appear rather constant from the cloud edge toward the center. The velocity structure function analysis is consistent with gas flows being dominated by the formation of hierarchical structures. The observations and analysis are consistent with a picture where the IRDC G28 is formed at the center of two converging gas flows. While the approximately constant mass flow rates are consistent with a self-similar, gravitationally driven collapse of the cloud, external compression by, e.g., spiral arm shocks or supernovae explosions cannot be excluded yet. Future investigations should aim at differentiating the origin of such converging gas flows.
We derive the fundamental parameters (temperature and luminosity) of 107619 Hipparcos stars and place these stars on a true Hertzsprung-Russell diagram. This is achieved by comparing BT-SETTL model atmospheres to spectral energy distributions (SEDs) created from Hipparcos, Tycho, Sloan Digital Sky Survey, DENIS, Two Micron All Sky Survey, MSX, AKARI, IRAS and Wide-field Infrared Survey Explorer data. We also identify and quantify from these SEDs any infrared excesses attributable to circumstellar matter. We compare our results to known types of objects, focusing on the giant branch stars. Giant star dust production (as traced by infrared excess) is found to start in earnest around 680L_{sun}_.
Mid-infrared extinction spectra (500-6000cm^-1^) of a series of single-component aerosol particle ensembles representative of those found in a range of planetary and lunar atmospheres are presented. The aerosols were generated in the laboratory via condensation from the gas phase in a bath gas cooling cell, and the spectra recorded using a Fourier transform infrared spectrometer. This paper is the first in a series aimed towards building a spectral database for use in remote sensing of aerosols. The aerosol substances included here are methane, ethane, propane, butane, pentane, ethylene, acetylene, carbon dioxide, ammonia and sulfur dioxide.
We present a sample of 1317 Infrared-faint radio sources (IFRSs) that, for the first time, are reliably detected in the infrared, generated by cross-correlating the Wide-field Infrared Survey Explorer (WISE) all-sky survey with major radio surveys. Our IFRSs are brighter in both radio and infrared than the first-generation IFRSs that were undetected in the infrared by the Spitzer Space Telescope. We present the first spectroscopic redshifts of IFRSs, and find that all but one of the IFRSs with spectroscopy have z>2. We also report the first X-ray counterparts of IFRSs, and present an analysis of radio spectra and polarization, and show that they include gigahertz peaked-spectrum, compact steep-spectrum and ultra-steep-spectrum sources. These results, together with their WISE infrared colours and radio morphologies, imply that our sample of IFRSs represents a population of radio-loud active galactic nuclei at z>2. We conclude that our sample consists of lower redshift counterparts of the extreme first-generation IFRSs, suggesting that the fainter IFRSs are at even higher redshift.
We present the near infrared spectra (0.9-2.5 micron) of protostellar jets (HH 24-26, HH72, BHR71). The observations were carried out with Sofi at R~600 with the 1x290arcsec slit. The spectra are dominated by H2 rovibrational lines (v up 5). Faint emission from ionized material in form of [FeII] and [SII] lines is also recognizable. The tables contain the observed lines together with the measured flux. The reported error derives from the rms of the baseline, multiplied by the width of the instrumental profile (30 Angstrom).
A search for infrared ring nebulae associated with regions of ionized hydrogen has been carried out. The New GPS Very Large Array survey at 20 cm forms the basis of the search, together with observations obtained with the Spitzer Space Telescope at 8 and 24um and the Herschel Space Telescope at 70um. Objects having ring-like morphologies at 8um and displaying extended emission at 20cm were selected visually. Emission at 24um having the form of an inner ring or central peak is also observed in the selected objects. A catalog of 99 ring nebulae whose shapes at 8 and 70um are well approximated by ellipses has been compiled. The catalog contains 32 objects whose shapes are close to circular (eccentricities of the fitted ellipses at 8um no greater than 0.6, angular radius exceeding 20"). These objects are promising for comparisons with the results of one-dimensional hydrodynamical simulations of expanding regions of ionized hydrogen.
We present a K-band atlas of 106 reflection nebulae, 41 of which are new discoveries. We observed these nebulae with the University of Hawaii 2.2m telescope in the course of an imaging survey of 197 objects that were selected as nearby young Class I sources. K-band images and flux-calibrated surface brightness contour plots of each nebula are presented.
To search for phase lags in the optical-infrared light curves of asymptotic giant branch stars, we have compared infrared data from the COBE DIRBE satellite with optical light curves from the AAVSO and other sources. We found 17 examples of phase lags between the times of infrared and optical maximum, and 4 stars with no observed lags.
Infrared photometry of all known members in Taurus
Short Name:
J/ApJ/784/126
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have compiled photometry at 3.4, 4.6, 12, and 22{mu}m from the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) for all known members of the Taurus complex of dark clouds. Using these data and photometry from the Spitzer Space Telescope, we have identified members with infrared excess emission from circumstellar disks and have estimated the evolutionary stages of the detected disks, which include 31 new full disks and 16 new candidate transitional, evolved, evolved transitional, and debris disks. We have also used the WISE All-Sky Source Catalog to search for new disk-bearing members of Taurus based on their red infrared colors. Through optical and near-infrared spectroscopy, we have confirmed 26 new members with spectral types of M1-M7. The census of disk-bearing stars in Taurus should now be largely complete for spectral types earlier than ~M8(M{>~}0.03M_{sun}_).
By using results from the 2MASS observation, the differences between the X-ray selected BL Lac objects (XBLs) and the radio selected ones (RBLs) in the near infrared are discussed in this paper. It is found that, statistically, the RBLs have redder near infrared colors and steeper spectral indices in the near infrared than XBLs, whereas the XBLs have more influences from their host galaxies than the RBLs. It is also seen that the RBLs have much brighter luminosity in the near infrared than the XBLs. In addition, the high polarization characteristics are found in common for RBLs, but not for XBLs.
