Related papers: Minimal HCN emission from Molecular Clouds in M33
A sample of 30 H2O extra-galactic maser galaxies with their published HCN(J=1-0) and HCO+(J=1-0) observations has been compiled to investigate the dense gas correlation with H2O maser emission. Our sample number exceeds the size of the…
Two selected regions in the molecular gas spiral arms in M51 were mapped with the Owens Valley Radio Observatory (OVRO) mm-interferometer in the 12CO(2-1), 13CO(1-0), C18O(1-0), HCN(1-0) and HCO+(1-0) emission lines. The CO data have been…
Cloud-cloud collision (CCC) has been proposed as a mechanism for triggering massive star formation. Observations in the Milky Way and nearby galaxies have revealed the presence of CCCs with collision velocity ($v_{\rm col}$) of 1-40 km/s,…
To explore the origin of high-velocity gas in the direction of the Large Magellanic Cloud (LMC) we analyze absorption lines in the ultraviolet spectrum of a Galactic halo star that is located in front of the LMC at d=9.2 kpc distance. We…
Using the HCN and HNC J=1--0 line observations, the abundance ratio of HCN/HNC has been estimated for different evolutionary stages of massive star formation: Infrared dark clouds (IRDCs), High-mass protostellar object (HMPOs), and…
We present single-dish (sub)millimeter observations of gas and dust in the Galactic high-mass star-forming region G19.61-0.23, with the aim of studying the large-scale properties and physical conditions of the molecular gas across the…
The evolution of giant molecular clouds (GMCs), the main sites of high-mass star formation, is an essential process to unravel the galaxy evolution. Using a GMC catalogue of M33 from ALMA-ACA survey, we classified 848 GMCs into three types…
The central kpc region of the low luminosity type-1 Seyfert galaxy NGC 1097 has been observed in the CO(1-0) and HCN(1-0) lines with the Nobeyama Millimeter Array and the NRO 45 m telescope. We find a striking enhancement of the HCN…
Molecular emission is used to investigate both the physical and chemical properties of protoplanetary disks. Therefore, to accurately derive disk properties, we need a thorough understanding of the behavior of the molecular probes we rely…
Using the {\it Hubble Space Telescope}/Space Telescope Imaging Spectrograph, ultraviolet (UV) extinction curves have been measured in M31 along thirteen new sightlines, increasing the M31 sample to seventeen. This sample covers a wide area…
We investigate the formation of stars within giant molecular clouds (GMCs) evolving in environments of different global magnetic field strength and large-scale dynamics. Building upon a series of magnetohydrodynamic (MHD) simulations of…
With the goal of deriving the physical and chemical conditions of star forming regions in the Large Magellanic Cloud (LMC), a spectral line survey of the prominent star forming region N113 is presented. The observations cover parts of the…
We present an analysis of the relation between the star formation rate (SFR) and mass of dense gas in Galactic clumps and nearby galaxies. Using the bolometric luminosity as a measure of SFR and the molecular line luminosity of HCO+ (3-2)…
Nuclear regions of ultraluminous and luminous infrared galaxies (U/LIRGs) are powered by starbursts and/or active galactic nuclei (AGNs). These regions are often obscured by extremely high columns of gas and dust. Molecular lines in the…
We report observations and an analysis of the distribution of HCO+(1-0) and HCO+(4-3) emission in the central 1 kpc star forming region of M82. Comparisons are made with other star formation indicators such as the mm continuum, the…
Recent studies have suggested that star formation (SF) in dense gas may be governed by essentially the same law in Galactic clouds and external galaxies. This conclusion remains controversial, however, because different tracers have been…
Stars generally form faster than the ambipolar diffusion time, suggesting that several processes short circuit the delay and promote a rapid collapse. These processes are considered here, including turbulence compression in the outer parts…
We attempt to make a complete census of massive-star formation within all of GMC G345.5+1.0. This cloud is located one degree above the galactic plane and at 1.8 kpc from the Sun, thus there is little superposition of dust along the…
We report new observations of the fundamental $J=1-0$ transition of HCl (at 625.918GHz) toward a sample of 25 galactic star-forming regions, molecular clouds, and evolved stars, carried out using the Caltech Submillimeter Observatory.…
Observations of molecular clouds, prestellar cores, and protoplanetary disks have established that the HNC/HCN ratio may be a potent diagnostic of molecular gas physical conditions. The processes that govern the relative abundances of these…