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We investigate the uncertainties affecting the temperature profiles of dense cores of interstellar clouds. In regions shielded from external ultraviolet radiation, the problem is reduced to the balance between cosmic ray heating, line…

Astrophysics of Galaxies · Physics 2015-05-30 M. Juvela , N. Ysard

Cosmic rays are an important source of heating in the interstellar medium, in particular in dense molecular cloud cores shielded from the external ultraviolet radiation field. The limits placed on the cosmic-ray ionization rate from…

Solar and Stellar Astrophysics · Physics 2015-02-12 Daniele Galli , Marco Padovani

Interstellar chemistry is important for galaxy formation, as it determines the rate at which gas can cool, and enables us to make predictions for observable spectroscopic lines from ions and molecules. We explore two central aspects of…

We carried out survey observations of HC$_{3}$N and HC$_{5}$N in the 42$-$45 GHz band toward 17 high-mass starless cores (HMSCs) and 35 high-mass protostellar objects (HMPOs) with the Nobeyama 45 m radio telescope. We have detected…

Astrophysics of Galaxies · Physics 2018-02-28 Kotomi Taniguchi , Masao Saito , T. K. Sridharan , Tetsuhiro Minamidani

It is often assumed that local sources of ionizing radiation have little impact on the distribution of HI in the post-reionization Universe. While this is a good assumption for the IGM, analytic arguments suggest that local sources may…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-27 Alireza Rahmati , Joop Schaye , Andreas H. Pawlik , Milan Raičević

Pulsars are remarkable objects that emit across the entire electromagnetic spectrum, providing a powerful probe of the interstellar medium. In this study, we investigate the relation between dispersion measure (DM) and X-ray absorption…

High Energy Astrophysical Phenomena · Physics 2015-06-15 C. He , C. -Y. Ng , V. M. Kaspi

Probability distribution functions (PDFs) of column densities are an established tool to characterize the evolutionary state of interstellar clouds. Using simulations, we show to what degree their determination is affected by noise,…

Instrumentation and Methods for Astrophysics · Physics 2016-05-25 Volker Ossenkopf-Okada , Timea Csengeri , Nicola Schneider , Christoph Federrath , Ralf S. Klessen

Nitrogen is one of the most abundant metals in the interstellar medium (ISM), and thus it constitutes an excellent test to study a variety of astrophysical environments, ranging from nova to active galactic nuclei. We present a detailed…

High Energy Astrophysical Phenomena · Physics 2021-05-12 Efrain Gatuzz , Javier A. García , Timothy R. Kallman

How cosmic rays sample the multi-phase interstellar medium (ISM) in starburst galaxies has important implications for many science goals, including evaluating the cosmic ray calorimeter model for these systems, predicting their neutrino…

High Energy Astrophysical Phenomena · Physics 2013-11-22 Erin Boettcher , Ellen G. Zweibel , Tova M. Yoast-Hull , J. S. Gallagher

Processing by interstellar photons affects the composition of the icy mantles on interstellar grains. The rate of photodissociation in solids differs from that of molecules in the gas phase. The aim of this work was to determine an average,…

Astrophysics of Galaxies · Physics 2018-05-16 Juris Kalvans

We compare observations of HI from the Very Large Array (VLA) and the Arecibo Observatory and observations of HCO$^+$ from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Northern Extended Millimeter Array (NOEMA) in the…

Accurately measuring the magnetic field in the ISM is essential for understanding star-formation processes. We searched archival data of the Submillimeter Array (SMA) for evidence of circular polarization in common molecular tracers, most…

Instrumentation and Methods for Astrophysics · Physics 2018-08-21 Mohammed Chamma , Martin Houde , Josep Miquel Girart , Ramprasad Rao

We present model calculations of ionization fractions for elements in the warm (log T = 4), low-density photoionized interstellar medium (WIM) of the Milky Way. We model the WIM as a combination of overlapping low-excitation H II regions…

Galactic cosmic rays are a ubiquitous source of ionisation of the interstellar gas, competing with UV and X-ray photons as well as natural radioactivity in determining the fractional abundance of electrons, ions and charged dust grains in…

High Energy Astrophysical Phenomena · Physics 2018-06-27 Marco Padovani , Alexei V. Ivlev , Daniele Galli , Paola Caselli

We present a comprehensive polarimetric study of 26 nearby molecular clouds in four far-infrared bands (53 $\mu$m to 214 $\mu$m) using 52 archival SOFIA/HAWC+ datasets. Far-infrared dust polarization observations probe the plane-of-sky…

Astrophysics of Galaxies · Physics 2026-03-11 Kaitlyn Karpovich , Susan E. Clark , Enrique Lopez-Rodriguez

We present a catalogue of molecular cloud cores drawn from high latitude, medium opacity clouds, using the all-sky IRAS Sky Survey Atlas (ISSA) images at 60 and 100~$\mu$m. The typical column densities of the cores are $ N(H_2)\sim 3.8…

Astrophysics · Physics 2009-10-31 N. E. Jessop , D. Ward-Thompson

The new era of high-resolution X-ray spectroscopy will significantly improve our understanding of the intra-cluster medium (ICM) by providing precise constraints on its underlying physical properties. However, spectral fitting requires…

Astrophysics of Galaxies · Physics 2026-02-11 Dimitris Chatzigiannakis , Annalisa Pillepich , Aurora Simionescu , Nhut Truong , Dylan Nelson

We examine 20 diffuse and translucent Galactic sight lines and extract the column densities of the ^12CO and ^13CO isotopologues from their ultraviolet A--X absorption bands detected in archival Space Telescope Imaging Spectrograph data…

Astrophysics · Physics 2009-11-13 Y. Sheffer , M. Rogers , S. R. Federman , D. L. Lambert , R. Gredel

We present a detailed study of the hydrogen density distribution in the local interstellar medium (ISM) using the X-ray absorption technique. Hydrogen column densities were precisely measured by fitting X-ray spectra from coronal sources…

High Energy Astrophysical Phenomena · Physics 2024-08-28 E. Gatuzz , J. Wilms , A. Zainab , S. Freund , P. C. Schneider , J. Robrade , S. Czesla , J. A. García , T. R. Kallmanınst

Context. The formation and destruction of molecules in the interstellar medium is a complex interplay between gas-phase reactions as well as processes on grain surfaces and within icy mantles. For many decades, the gas-phase composition of…