Related papers: X-ray chemistry in envelopes around young stellar …
In the local Universe, integrated X-ray emission from high-mass X-ray binaries (HMXBs) is dominated by the brightest ultraluminous X-ray sources (ULXs) with luminosity >10^40 erg/s. Such rare objects probably also dominated the production…
Cosmic-rays are the primary initiators of interstellar chemistry, and getting a better understanding of the varying impact they have on the chemistry of interstellar clouds throughout the Milky Way will not only expand our understanding of…
The yellow hypergiant stars (YHGs) are very massive objects that are expected to pass through periods of intense mass loss during their evolution. Despite of this, massive circumstellar envelopes have been found only in two of them,…
Astronomical observations of flares from analogs of the early Sun have the potential to give critical insights into the high energy irradiation environment of protoplanetary disks. Solar-mass young stellar objects are significantly more…
Although the environments of star and planet formation are thermodynamically cold, substantial X-ray emission from 10-100 MK plasmas is present. In low mass pre-main sequence stars, X-rays are produced by violent magnetic reconnection…
The first generation of stars (commonly known as population III) are expected to form in low-mass protogalaxies in which molecular hydrogen is the dominant coolant. Radiation from these stars will rapidly build up an extragalactic…
The origin and evolution of the X-rays in very young stellar objects (YSOs) are not yet well understood since it is very hard to observe YSOs in the protostellar phase. We study the X-ray properties of Class 0-I objects in the Orion Nebula…
The presence of soft x-rays is very important for the chemical evolution of interstellar medium and other astrophysical environments close to young and bright stars. Soft X-rays can penetrate deep in molecular clouds and protostellar disks…
Observations of the Ly-alpha forest at z~3 reveal an average metallicity Z~0.01 Z_solar. The high-redshift supernovae that polluted the IGM also accelerated relativistic electrons. Since the energy density of the CMB scales as (1+z)^4, at…
The infrared [Ne II] and [Ne III] fine structure lines at 12.81um and 15.55um are predicted to trace the circumstellar disk gas subject to X-ray heating and ionization. We investigate the origin of these lines by comparing observations with…
Context. Ionization plays a central role in the gas-phase chemistry of molecular clouds. Since ions are coupled with magnetic fields, which can in turn counteract gravitational collapse, it is of paramount importance to measure their…
Chandra ACIS-I data of the molecular cloud and HII region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto et al. 2000) were resolved into 792 point sources. After removing the point sources, an extended…
When the neutral interstellar medium is exposed to EUV and soft X ray radiation, the argon atoms in it are far more susceptible to being ionized than the hydrogen atoms. We make use of this fact to determine the level of ionization in the…
Low-mass young stellar objects are powerful emitters of X-rays that can ionize and heat the disks and the young planets they harbour. The X-rays produce molecular ions that affect the chemistry of the disk atmospheres and their…
Chemistry in diffuse molecular clouds relies primarily on rapid ion-molecule reactions. Formation of the initial ions, H$^+$ and H$_2^+$, is dominated by cosmic-ray ionization of H and H$_2$, making the cosmic-ray ionization rate (denoted…
Most star formation in our galaxy occurs within embedded clusters, and these background environments can affect the star and planet formation processes occurring within them. In turn, young stellar members can shape the background…
The interstellar medium of galaxies, with temperatures reaching several million degrees, provides a pivotal perspective for understanding the physical and chemical properties of star formation, galactic evolution, and their associated…
We present a far-ultraviolet (PDR) and an X-ray dominated region (XDR) code. We include and discuss thermal and chemical processes that pertain to irradiated gas. An elaborate chemical network is used and a careful treatment of PAHs and H2…
Molecular clouds interacting with supernova remnants may be subject to a greatly enhanced irradiation by cosmic rays produced at the shocked interface between the ejecta and the molecular gas. Over the past decade, broad-band observations…
In this paper we discuss the X-ray properties of 49 local (z<0.035) Seyfert 2 galaxies with HST/WFC2 high-resolution optical coverage. It includes the results of 26 still unpublished Chandra and XMM-Newton observations, which yield 25 (22)…