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- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2601
- Title:
- CO lines in luminous IR galaxies
- Short Name:
- J/MNRAS/426/2601
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from a large molecular line survey of luminous infrared galaxies (LIRGs; L_IR_>~10^11^L_{sun}_) in the local Universe (z<=0.1), conducted during the last decade with the James Clerk Maxwell Telescope and the IRAM 30-m telescope. This work presents the CO and ^13^CO line data for 36 galaxies, further augmented by multi-J total CO line luminosities available for other infrared (IR) bright galaxies from the literature. This yields a combined sample of N=70 galaxies with the star formation (SF) powered fraction of their IR luminosities spanning L^(*)^IR_~10^10^-2x10^12^)L_{sun}_ and a wide range of morphologies.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A41
- Title:
- CO line survey in 0.2<z<1 of galaxies
- Short Name:
- J/A+A/550/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After new observations of 39 galaxies at z=0.6-1.0 obtained at the IRAM 30m telescope, we present our full CO line survey covering the redshift range 0.2<z<1. Our aim is to determine the driving factors accounting for the steep decline in the star formation rate during this epoch. We study both the gas fraction, defined as Mgas/(Mgas+Mstar), and the star formation efficiency (SFE) defined by the ratio between far-infrared luminosity and molecular gas mass (L_FIR_/M(H_2_), i.e. a measure for the inverse of the gas depletion time. The sources are selected to be ultra-luminous infrared galaxies (ULIRGs), with L_FIR_ greater than 10^12^L_{sun}_, and experiencing starbursts. When we adopt a standard ULIRG CO-to-H_2_ conversion factor, their molecular gas depletion time is less than 100Myr. Our full survey has now filled the gap of CO observations in the 0.2<z<1 range covering almost half of cosmic history. The detection rate in the 0.6<z<1 interval is 38% (15 galaxies out of 39), compared to 60% for the 0.2<z<0.6 interval. The average CO luminosity is L'_CO_=1.8x10^10^K.km/s.pc^2^, corresponding to an average H_2_ mass of 1.45x10^10^M_{sun}_. From observation of 7 galaxies in both CO(2-1) and CO(4-3), a high gas excitation has been derived; together with the dust mass estimation, this supports the choice of our low ULIRG conversion factor between CO luminosity and H_2_ for our sample sources. We find that both the gas fraction and the SFE significantly increase with redshift, by factors of 3+/-1 from z=0 to 1, and therefore both quantities play an important role and complement each other in cosmic star formation evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/130
- Title:
- Collinder 261 Chandra sources & optical counterparts
- Short Name:
- J/ApJ/837/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of Collinder 261 (Cr261), which at an age of 7Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr261, and reaches a limiting X-ray luminosity of L_X_~4x10^29^erg/s (0.3-7keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r_h_, and we estimate that among the sources with L_X_>~10^30^erg/s, ~26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of Cr261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr261 has an approximate mass of 6500M_{sun}_, roughly the same as the old open cluster NGC6791. The X-ray emissivity of Cr261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.
- ID:
- ivo://CDS.VizieR/J/A+A/418/525
- Title:
- Collinder 232 & Trumpler 14/16 UBVRI photometry
- Short Name:
- J/A+A/418/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present and analyze new CCD UBVRI photometry down to V~21 in the region of the young open cluster Collinder 232, located in the Carina spiral arm, and discuss its relationship to Trumpler 14 and Trumpler 16, the two most prominent young open clusters located in the core of NGC 3372 (the Carina Nebula).
- ID:
- ivo://CDS.VizieR/J/A+A/536/A63
- Title:
- Collinder 69 very low mass stars and brown dwarfs
- Short Name:
- J/A+A/536/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied age dependent features in optical and near-infrared spectra of candidate members to the cluster (such as alkali lines and accretion associated indicators). In addition, we have complemented that study with the analysis of other youth indicators like X-ray emission or mid-infrared excess. We have confirmed the membership to Collinder 69 of ~90 photometric candidate members. As a byproduct we have determined a temperature scale for young M, very low-mass stars and brown dwarfs. We have assembled one of the most complete Initial Mass Functions from 0.016 to 20M_{sun}_. And, finally, we have studied the implications of the spatial distribution of the confirmed members on the proposed mechanisms of brown dwarfs formation.
- ID:
- ivo://CDS.VizieR/J/A+A/526/A21
- Title:
- Collinder 69 X-ray sources
- Short Name:
- J/A+A/526/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper of a series devoted to the {lambda} Orionis star-forming region, Orion's Head, from the X-ray perspective. Our final aim is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. We aim to uncover the population of the central, young star cluster Collinder 69, and in particular those diskless Class III objects not identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A121
- Title:
- Collisional effects in blue wing of Balmer-alpha
- Short Name:
- J/A+A/657/A121
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In order to investigate the near wing of the Lyman-{alpha} line, accurate line profile calculations and molecular data are both required due to the existence of a close line satellite responsible for its asymmetrical shape. Lyman-{alpha} lines observed with the Cosmic Origin Spectograph (COS) on the Hubble Space Telescope (HST) show this peculiarity in the spectra of DBA and DA white dwarf stars. A similar asymmetrical shape in the blue wing can be predicted in the Balmer-{alpha} line of H perturbed by He and H atoms. In continuation with a very recent work on the Lyman-{alpha} line, where the n = 2 potential energies and transition dipole moments from the ground state were determined, we present new accurate H-He potential energies and electronic transition dipole moments involving the molecular states correlated with H(n=3)+He and their transition dipole moments with the states correlated with H(n=2)+He. Those new data and existing molecular data for H(n=2,3)-H are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-{alpha} line of H perturbed by He and H atoms. We note the consequences for the Balmer-{alpha} line shape in the physical conditions found in the cool atmosphere of DZA white dwarfs where helium densities may be as high as 10^21^cm^-3^. This study is undertaken with a unified theory of spectral line broadening valid at very high helium densities.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A103
- Title:
- Collisional excitation of sulfur dioxide
- Short Name:
- J/A+A/531/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present collisional rate coefficients for SO_2_ with ortho and para molecular hydrogen for the physical conditions prevailing in dark molecular clouds. Rate coefficients for the first 31 rotational levels of this species (energies up to 55K) and for temperatures between 5 and 30K are provided. We have found that these rate coefficients are about ten times more than those previously computed for SO_2_ with helium. We calculated the expected emission of the centimeter wavelength lines of SO_2_. We find that the transition connecting the metastable 2_02_ level with the 111 one is in absorption against the cosmic background for a wide range of densities. The 4_04_-3_13_ line is found to be inverted for densities below a few 10^4^cm^-3^. We observed the 1_11_-2_02_ transition with the 100m Green Bank Telescope towards some dark clouds. The line is observed, as expected, in absorption and provides an abundance of SO_2_ in these objects of a few 10^-10^. The potential use of millimeter lines of SO_2_ as tracers of the physical conditions of dark clouds is discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/492/257
- Title:
- Collisional excitation of water in warm media
- Short Name:
- J/A+A/492/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interpretation of water line emission from infrared and submillimetre observations requires a detailed knowledge of collisional rate coefficients over a wide range of levels and temperatures. We attempt to determine rotational and rovibrational rate coefficients for H_2_O colliding with both H_2_ and electrons in warm, molecular gas. Pure rotational rates are derived by extrapolating published data using a new method partly based on the information (phase space) theory of Levine and co-workers. Ro-vibrational rates are obtained using vibrational relaxation data available in the literature and by assuming a complete decoupling of rotation and vibration. Results. Rate coefficients were obtained for the lowest 824 ro-vibrational levels of H_2_O in the temperature range 200-5000K. Our data is expected to be accurate to within a factor of ~5 for the highest rates (>10^-11^cm^3^/s). Smaller rates, including the ro-vibrational ones, should be generally accurate to within an order of magnitude. As a first application of this data, we show that vibrationally excited water emission observed in evolved stars is expected to be at least partly excited by means of collisions.