scholarly journals Discovery of Carbon Radio Recombination Lines in M82

2014 ◽  
Vol 10 (S309) ◽  
pp. 141-144
Author(s):  
Leah K. Morabito ◽  
J. B. R. Oonk ◽  
Francisco Salgado ◽  
M. Carmen Toribio ◽  
Xander Tielens ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Neutral Medium ◽  
Radio Recombination Lines ◽  
Evolution Of Galaxies

AbstractCold, diffuse HI clouds are a key component of the interstellar medium (ISM), and play an important role in the evolution of galaxies. Carbon radio recombination lines (CRRLs) trace this ISM stage, and with the enormous sensitivity of LOFAR we have already begun to map and constrain the physical properties of this gas in our own Galaxy. Using LOFAR's low band antenna, we have observed M 82 and present the first ever extragalactic detection of CRRLs. We stack 22 lines to find a 8.5-sigma detection. The line peak to continuum ratio is ∼0.003, with a FWHM of 31 km s−1. The CRRL feature is consistent with an origin in the cold, neutral medium in the direction of the nucleus of M 82.

scholarly journals A Reference Sample: ISM of the Most Isolated Galaxies

2004 ◽  
Vol 217 ◽  
pp. 220-221
Author(s):  
L. Verdes-Montenegro ◽  
J. Sulentic ◽  
D. Espada ◽  
S. Leon ◽  
U. Lisenfeld ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Galaxy Evolution ◽  
Reference Sample ◽  
Control Sample ◽  
Evolution Of Galaxies ◽  
Isolated Galaxies ◽  
Internal Evolution

We are constructing the first complete unbiased control sample of the most isolated galaxies of the northern sky to serve as a template in the study of star formation and galaxy evolution in denser environments. Our goal is to compare and quantify the properties of different phases of the interstellar medium in this sample, as well as the level of star formation, both relevant parameters in the internal evolution of galaxies and strongly conditioned by the environment. To achieve this goal we are building a multiwavelength database for this sample to compare and quantify the properties of different phases of the ISM.

scholarly journals Analysis of the Interstellar Medium Properties of the Herschel Reference Survey Galaxies

2012 ◽  
Vol 8 (S292) ◽  
pp. 284-284
Author(s):  
Laure Ciesla ◽  
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Radiation Field ◽  
Statistical Study ◽  
Dust Mass ◽  
Multi Wavelength ◽  
Nearby Galaxies ◽  
Photodissociation Regions ◽  
K Band

AbstractThe Herschel Reference Survey is a guaranteed time key project aimed at studying the physical properties of the interstellar medium (ISM) of 323 nearby galaxies, covered by multi-wavelength data. This volume limited, K-band selected sample is composed of galaxies spanning the whole range of morphological types and environments. We conduct a statistical study on the ISM properties of nearby galaxies based on the analysis of their SED. To achieve this goal, we fit the data with the models of Draine & Li (2007) to obtain the intensity of interstellar radiation field, the PAH abundance, the contribution of photodissociation regions, and the dust mass.

scholarly journals INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

2021 ◽  
Vol 26 (4) ◽  
pp. 314-325
Author(s):  
S. V. Stepkin ◽  
◽  
O. O. Konovalenko ◽  
Y. V. Vasylkivskyi ◽  
D. V. Mukha ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Recombination Mechanism ◽  
Radio Recombination Lines ◽  
Radio Spectroscopy ◽  
Correlation Spectrum

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

scholarly journals Massive stars shaping the ISM: H I holes and shells in nearby galaxies

1999 ◽  
Vol 193 ◽  
pp. 636-644
Author(s):  
Elias Brinks ◽  
Fabian Walter
Keyword(s):  
Interstellar Medium ◽  
Dwarf Galaxy ◽  
Massive Stars ◽  
Neutral Hydrogen ◽  
Neutral Medium ◽  
Stellar Winds ◽  
X Ray ◽  
Left Behind ◽  
Neutral Gas ◽  
Nearby Galaxies

Neutral hydrogen (H I) is a magnificent tool when studying the structure of the interstellar medium (ISM) as it is relatively easily observable and can be mapped at good spatial and velocity resolution with modern instruments. Moreover, it traces the cool (∼ 100 K) and warm (∼ 5000 K) neutral gas which together make up about 60%, or the bulk, of the ISM. The currently accepted picture is that stellar winds and subsequent supernovae are the origin for the clearly defined holes or bubbles within the more or less smooth neutral medium. The H I can therefore serve indirectly as a tracer of the hot interstellar medium (HIM) left behind after the most massive stars within an OB association have gone off as supernovae. A splendid example is the dwarf galaxy IC 2574 for which we discuss H I, optical and X-ray observations.

scholarly journals Penetration of Interstellar Dust Aggregates Into Circumstellar Dust Disks

2004 ◽  
Vol 202 ◽  
pp. 347-349
Author(s):  
Hiroshi Kimura ◽  
Ingrid Mann
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Relative Motion ◽  
Interstellar Dust ◽  
Dust Particles ◽  
Circumstellar Dust ◽  
Circumstellar Disk ◽  
Dust Disks

Interstellar dust particles, which are supposedly aggregates, penetrate dust disks around stars because of the star's motion relative to the surrounding interstellar medium (ISM). We discuss the interrelation of the physical properties of local interstellar dust, the relative motion of the star and the surrounding ISM, and the evolution of the circumstellar disk.

scholarly journals Studying the Interstellar Medium of H II/BCD Galaxies Using IFU Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Patricio Lagos ◽  
Polychronis Papaderos
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Starburst Galaxies ◽  
Chemical Abundances ◽  
Spatially Resolved ◽  
Low Mass ◽  
Field Unit ◽  
Integral Field

We review the results from our studies, and previous published work, on the spatially resolved physical properties of a sample of Hii/BCD galaxies, as obtained mainly from integral-field unit spectroscopy with Gemini/GMOS and VLT/VIMOS. We confirm that, within observational uncertainties, our sample galaxies show nearly spatially constant chemical abundances similar to other low-mass starburst galaxies. They also show Heii  λ4686 emission with the properties being suggestive of a mix of excitation sources and with Wolf-Rayet stars being excluded as the primary ones. Finally, in this contribution, we include a list of all Hii/BCD galaxies studied thus far with integral-field unit spectroscopy.

scholarly journals Cloud formation in the atomic and molecular phase: H I self absorption (HISA) towards a giant molecular filament

2020 ◽  
Vol 634 ◽  
pp. A139 ◽  
Author(s):  
Y. Wang ◽  
S. Bihr ◽  
H. Beuther ◽  
M. R. Rugel ◽  
J. D. Soler ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Power Law ◽  
Molecular Clouds ◽  
Column Density ◽  
Cloud Formation ◽  
Neutral Medium ◽  
Molecular Component ◽  
Density Peaks ◽  
Log Normal ◽  
High Column

Molecular clouds form from the atomic phase of the interstellar medium. However, characterizing the transition between the atomic and the molecular interstellar medium (ISM) is a complex observational task. Here we address cloud formation processes by combining H I self absorption (HISA) with molecular line data. Column density probability density functions (N-PDFs) are a common tool for examining molecular clouds. One scenario proposed by numerical simulations is that the N-PDF evolves from a log-normal shape at early times to a power-law-like shape at later times. To date, investigations of N-PDFs have been mostly limited to the molecular component of the cloud. In this paper, we study the cold atomic component of the giant molecular filament GMF38.1-32.4a (GMF38a, distance = 3.4 kpc, length ~ 230 pc), calculate its N-PDFs, and study its kinematics. We identify an extended HISA feature, which is partly correlated with the 13CO emission. The peak velocities of the HISA and 13CO observations agree well on the eastern side of the filament, whereas a velocity offset of approximately 4 km s−1 is found on the western side. The sonic Mach number we derive from the linewidth measurements shows that a large fraction of the HISA, which is ascribed to the cold neutral medium (CNM), is at subsonic and transonic velocities. The column density of the CNM part is on the order of 1020 to 1021 cm−2. The column density of molecular hydrogen, traced by 13CO, is an order of magnitude higher. The N-PDFs from HISA (CNM), H I emission (the warm and cold neutral medium), and 13CO (molecular component) are well described by log-normal functions, which is in agreement with turbulent motions being the main driver of cloud dynamics. The N-PDF of the molecular component also shows a power law in the high column-density region, indicating self-gravity. We suggest that we are witnessing two different evolutionary stages within the filament. The eastern subregion seems to be forming a molecular cloud out of the atomic gas, whereas the western subregion already shows high column density peaks, active star formation, and evidence of related feedback processes.

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