Related papers: Neutral chlorine and molecular hydrogen at high re…
The transition between atomic and molecular hydrogen is associated with important changes in the structure of interstellar clouds, and marks the beginning of interstellar chemistry. Because of the relatively simple networks controlling…
(Abridged for arXiv) We report the discovery of an unusual, extremely dust-rich and metal-strong damped \lya absorption system (DLA) at a redshift $z_{a}=2.4596$ toward the quasar SDSS J115705.52+615521.7 (hereafter J1157+6155) with an…
We report additional detections of the chloronium molecular ion, H$_2$Cl$^+$, toward four bright submillimeter continuum sources: G29.96, W49N, W51, and W3(OH). With the use of the HIFI instrument on the Herschel Space Observatory, we…
We present chemical abundance measurements from medium resolution observations of 8 sub-damped Lyman-alpha absorber and 2 strong Lyman-limit systems at z < 1.5 observed with the MIKE spectrograph on the 6.5m Magellan II Clay telescope.…
We report the discovery of a threshold in the HI column density of Galactic gas clouds below which the formation of the cold phase of HI is inhibited. This threshold is at $N_{HI} = 2 \times 10^{20}$ per cm$^{2}$; sightlines with lower HI…
Observations are presented of emission lines from organic molecules at frequencies 32 - 50 GHz in the vicinity of Chamaeleon MMS1. This chemically-rich dense cloud core habours an extremely young, very low-luminosity protostellar object and…
Chlorine abundances are reported in 15 evolved giants and one M dwarf in the solar neighborhood. The Cl abundance was measured using the vibration-rotation 1-0 P8 line of H$^{35}$Cl at 3.69851 $\mu$m. The high resolution L-band spectra were…
We present a pipeline based on a random forest classifier for the identification of high column-density clouds of neutral hydrogen (i.e. the Lyman limit systems, LLSs) in absorption within large spectroscopic surveys of z>3 quasars. We test…
We have complemented existing observations of HI absorption with new observations of HCO$^+$, C$_2$H, HCN, and HNC absorption from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Northern Extended Millimeter Array (NOEMA) in…
Context. Neutral atomic hydrogen (HI) absorption lines can be used to probe the cold neutral medium (CNM) at high Galactic latitudes. Cold HI with a significant optical depth from the GASKAP-HI survey is found to be located predominantly if…
We used our database of ESO VLT-UVES spectra of quasars to build up a sample of 67 Damped Lyman-alpha (DLA) systems with redshifts 1.7<zabs<3.7. For each system, we measured average metallicities relative to Solar, [X/H] (with either X=Zn,…
We are encouraged by the improving abundance measurements for quasar damped absorption line systems to start a new study of galaxy chemical evolution from high to low redshifts. Our goal is a simple, robust model based on a synthesis of our…
We study the high column density regime of the HI column density distribution function and argue that there are two distinct features: a turnover at NHI ~ 10^21 cm^-2 which is present at both z=0 and z ~ 3, and a lack of systems above NHI ~…
We probe the column densities and masses traced by the ionized and neutral atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [C I] and low-$J$ CO lines toward the star-forming…
From the first published z > 3 survey of 21-cm absorption within the hosts of radio galaxies and quasars, we found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to…
Molecular hydrogen is quite underabundant in damped Lyman-alpha systems at high redshift, when compared to the interstellar medium near the Sun. This has been interpreted as implying that the gas in damped Lyman-alpha systems is warm. like…
Recent submillimeter and far-infrared wavelength observations of absorption in the rotational ground-state lines of various simple molecules against distant Galactic continuum sources have opened the possibility of studying the chemistry of…
We use high signal-to-noise ratio, high-resolution VLT-UVES data of Q J0643-5041 amounting to a total of more than 23 hours exposure time and fit the neutral hydrogen, metals and H2 absorption features with multiple-component Voigt…
Damped Lyman alpha systems seen in the spectra of high-z QSOs arise in high-density neutral gas in which molecular hydrogen (H_2) should be conspicuous. Systematic searches to detect the H_2 lines redshifted into the Lyman alpha forest at…
We report new near-infrared and mm-wave observational data on a selection of massive Galactic molecular clumps (part of the CHaMP sample) and their associated young star clusters. The clumps show, for the first time in a "dense gas tracer",…