Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAn Atomic and Molecular Study of the Interstellar Medium Around the SNR RCW 103
160
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report on the detection of HCO+ and 12CO emission in the rotational transition J=1-0 in the vicinity of the shock front at the southern border of the supernova remnant RCW 103, where previous infrared observations suggest an interaction with a molecular cloud. The observations were carried out with the Australian Millimeter Radiotelescope at Mopra. We observed a depletion of HCO+ behind the supernova shock front. In addition, we studied the interstellar medium over an extended region towards RCW 103 based on archival 21 cm HI line observations from the Australia Telescope Compact Array (ATCA) and the Parkes Telescope. No atomic gas is observed in emission in coincidence with the molecular feature. This absence is interpreted in terms of self absorption processes.
rate research
Read More
We have carried out a study of the neutral hydrogen in the direction of the X-ray source 1E 161348-5055, a compact central object (CCO) located in the interior of the supernova remnant (SNR) RCW 103. The HI 21 cm line observations were carried out using the Australia Telescope Compact Array, complemented with single dish data from the Parkes radio telescope to recover information at all spatial scales. We derive a distance to RCW 103 of 3.3 kpc, in agreement with previous distance measurements. We have also detected a small hole in the HI emission which is positionally and kinematically coincident with the location of the CCO which confirms the association between the SNR and the CCO. This is the third case of a depression in HI emission seemingly associated with CCOs in SNRs. The characteristic parameters of the holes such as their size, eccentricity and evacuated mass are similar in all three cases. We estimate the absorbing HI column density towards 1E 161348-5055 to be ~6 x 10^{21} cm^{-2}, a value compatible with a blackbody solution for the CCO X-ray emission. However, the implied brightness temperature is very high comparedto most neutron stars. Moreover, the strong long-term variability in X-rays favours the hypothesis that 1E 161348-5055 is an accreting binary sourcerather than an isolated, cooling neutron star. An analysis of the continuum image obtained at 1.4 GHz from these observations shows no trace of a pulsar wind nebula around 1E 161348-5055, in spite of it being a young object.
The H II region RCW120 is a well-known object, which is often considered as a target to verify theoretical models of gas and dust dynamics in the interstellar medium. However, the exact geometry of RCW120 is still a matter of debate. In this work, we analyse observational data on molecular emission in RCW120 and show that 13CO(2-1) and C18O(2-1) lines are fitted by a 2D model representing a ring-like face-on structure. The changing of the C18O(3-2) line profile from double-peaked to single-peaked from the dense molecular Condensation 1 might be a signature of stalled expansion in this direction. In order to explain a self-absorption dip of the 13CO(2-1) and 13CO(3-2) lines, we suggest that RCW120 is surrounded by a diffuse molecular cloud, and find confirmation of this cloud on a map of interstellar extinction. Optically thick 13CO(2-1) emission and the infrared 8 um PAH band form a neutral envelope of the H II region resembling a ring, while the envelope breaks into separate clumps on images made with optically thin C18O(2-1) line and far-infrared dust emission.
We present a comprehensive analysis of interstellar absorption lines seen in moderately-high resolution, high signal-to-noise ratio optical spectra of SN 2014J in M82. Our observations were acquired over the course of six nights, covering the period from ~6 days before to ~30 days after the supernova reached its maximum B-band brightness. We examine complex absorption from Na I, Ca II, K I, Ca I, CH+, CH, and CN, arising primarily from diffuse gas in the interstellar medium (ISM) of M82. We detect Li I absorption over a range in velocity consistent with that exhibited by the strongest Na I and K I components associated with M82; this is the first detection of interstellar Li in a galaxy outside of the Local Group. There are no significant temporal variations in the absorption-line profiles over the 37 days sampled by our observations. The relative abundances of the various interstellar species detected reveal that the ISM of M82 probed by SN 2014J consists of a mixture of diffuse atomic and molecular clouds characterized by a wide range of physical/environmental conditions. Decreasing N(Na I)/N(Ca II) ratios and increasing N(Ca I)/N(K I) ratios with increasing velocity are indicative of reduced depletion in the higher-velocity material. Significant component-to-component scatter in the N(Na I)/N(Ca II) and N(Ca I)/N(Ca II) ratios may be due to variations in the local ionization conditions. An apparent anti-correlation between the N(CH+)/N(CH) and N(Ca I)/N(Ca II) ratios can be understood in terms of an opposite dependence on gas density and radiation field strength, while the overall high CH+ abundance may be indicative of enhanced turbulence in the ISM of M82. The Li abundance also seems to be enhanced in M82, which supports the conclusions of recent gamma-ray emission studies that the cosmic-ray acceleration processes are greatly enhanced in this starburst galaxy.
RCW 86 is a young supernova remnant (SNR) showing a shell-type structure at several wavelengths and is thought to be an efficient cosmic-ray (CR) accelerator. Earlier textit{Fermi} Large Area Telescope results reported the detection of $gamma$-ray emission coincident with the position of RCW 86 but its origin (leptonic or hadronic) remained unclear due to the poor statistics. Thanks to 6.5 years of data acquired by the textit{Fermi}-LAT and the new event reconstruction Pass 8, we report the significant detection of spatially extended emission coming from RCW 86. The spectrum is described by a power-law function with a very hard photon index ($Gamma = 1.42 pm 0.1_{rm stat} pm 0.06_{rm syst}$) in the 0.1--500 GeV range and an energy flux above 100 MeV of ($2.91$ $pm$ $0.8_{rm stat}$ $pm$ $0.12_{rm syst}$) $times$ $10^{-11}$ erg cm$^{-2}$ s$^{-1}$. Gathering all the available multiwavelength (MWL) data, we perform a broadband modeling of the nonthermal emission of RCW 86 to constrain parameters of the nearby medium and bring new hints about the origin of the $gamma$-ray emission. For the whole SNR, the modeling favors a leptonic scenario in the framework of a two-zone model with an average magnetic field of 10.2 $pm$ 0.7 $mu$G and a limit on the maximum energy injected into protons of 2 $times$ 10$^{49}$ erg for a density of 1 cm$^{-3}$. In addition, parameter values are derived for the North-East (NE) and South-West (SW) regions of RCW 86, providing the first indication of a higher magnetic field in the SW region.
We discuss the absorption due to various constituents of the interstellar medium of M82 seen in moderately high resolution, high signal-to-noise ratio optical spectra of SN 2014J. Complex absorption from M82 is seen, at velocities 45 $le$ $v_{rm LSR}$ $le$ 260 km s$^{-1}$, for Na I, K I, Ca I, Ca II, CH, CH$^+$, and CN; many of the diffuse interstellar bands (DIBs) are also detected. Comparisons of the column densities of the atomic and molecular species and the equivalent widths of the DIBs reveal both similarities and differences in relative abundances, compared to trends seen in the ISM of our Galaxy and the Magellanic Clouds. Of the ten relatively strong DIBs considered here, six (including $lambda$5780.5) have strengths within $pm$20% of the mean values seen in the local Galactic ISM, for comparable N(K I); two are weaker by 20--45% and two (including $lambda$5797.1) are stronger by 25--40%. Weaker than expected DIBs [relative to N(K I), N(Na I), and E(B-V)] in some Galactic sight lines and toward several other extragalactic supernovae appear to be associated with strong CN absorption and/or significant molecular fractions. While the N(CH)/N(K I) and N(CN)/N(CH) ratios seen toward SN 2014J are similar to those found in the local Galactic ISM, the combination of high N(CH$^+$)/N(CH) and high W(5797.1)/W(5780.5) ratios has not been seen elsewhere. The centroids of many of the M82 DIBs are shifted, relative to the envelope of the K I profile -- likely due to component-to-component variations in W(DIB)/N(K I) that may reflect the molecular content of the individual components. We compare estimates for the host galaxy reddening E(B-V) and visual extinction A$_{rm V}$ derived from the various interstellar species with the values estimated from optical and near-IR photometry of SN 2014J.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
