To see the other types of publications on this topic, follow the link: HII regions;supernova remnants;radio lines.
Journal articles on the topic 'HII regions;supernova remnants;radio lines'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 28 journal articles for your research on the topic 'HII regions;supernova remnants;radio lines.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Argo, M. K., A. Pedlar, T. W. B. Muxlow, and R. J. Beswick. "OH main line masers in the M 82 starburst." Proceedings of the International Astronomical Union 3, S242 (March 2007): 427–31. http://dx.doi.org/10.1017/s1743921307013543.
Full textAbstract:
AbstractA study of the distribution of OH gas in the central region of the nearby active starburst galaxy M82 has confirmed two previously known bright masers and revealed several new main line masers. Three of these are seen only at 1665 MHz, one is detected only at 1667 MHz, while the rest are detected in both lines. Observations covering both the 1665 and 1667 MHz lines, conducted with both the Very Large Array (VLA) and the Multi-Element Radio Linked Interferometer Network (MERLIN), have been used to accurately measure the positions and velocities of these features. This has allowed a comparison with catalogued continuum features in the starburst such as HII regions and supernova remnants, as well as known water and satellite line OH masers. Most of the main line masers appear to be associated with known HII regions although the two detected only at 1665 MHz are seen along the same line of sight as known supernova remnants.
2
Supan, L., G. Castelletti, W. M. Peters, and N. E. Kassim. "G51.04+0.07 and its environment: Identification of a new Galactic supernova remnant at low radio frequencies." Astronomy & Astrophysics 616 (August 2018): A98. http://dx.doi.org/10.1051/0004-6361/201832995.
Full textAbstract:
We have identified a new supernova remnant (SNR), G51.04+0.07, using observations at 74 MHz from the Very Large Array Low-Frequency Sky Survey Redux (VLSSr). Earlier, higher frequency radio continuum, recombination line, and infrared data had correctly inferred the presence of nonthermal radio emission within a larger, complex environment including ionised nebulae and active star formation. However, our observations have allowed us to redefine at least one SNR as a relatively small source (7.′5 × 3′in size) located at the southern periphery of the originally defined SNR candidate G51.21+0.11. The integrated flux density of G51.04+0.07 at 74 MHz is 6.1 ± 0.8 Jy, while its radio continuum spectrum has a slope α = −0.52 ± 0.05 (S v ∝ vα), typical of a shell-type remnant. We also measured spatial variations in the spectral index between 74 and 1400 MHz across the source, ranging from a steeper spectrum (α = −0.50 ± 0.04) coincident with the brightest emission to a flatter component (α = −0.30 ± 0.07) in the surrounding fainter region. To probe the interstellar medium into which the redefined SNR is likely evolving, we have analysed the surrounding atomic and molecular gas using the 21 cm neutral hydrogen (HI) and 13CO(J = 1 − 0) emissions. We found that G51.04+0.07 is confined within an elongated HI cavity and that its radio emission is consistent with the remains of a stellar explosion that occurred ~6300 yr ago at a distance of 7.7 ± 2.3 kpc. Kinematic data suggest that the newly discovered SNR lies in front of HII regions in the complex, consistent with the lack of a turnover in the low frequency continuum spectrum. The CO observations revealed molecular material that traces the central and northern parts of G51.04+0.07. The interaction between the cloud and the radio source is not conclusive and motivates further study. The relatively low flux density (~1.5 Jy at 1400 MHz) of G51.04+0.07 is consistent with this and many similar SNRs lying hidden along complex lines of sight towards inner Galactic emission complexes. It would also not be surprising if the larger complex studied here hosted additional SNRs.
3
Chu, You-Hua, and Robert C. Kennicutt. "Supernova Remnants in Giant HII Regions." International Astronomical Union Colloquium 101 (1988): 201–4. http://dx.doi.org/10.1017/s0252921100102374.
Full textAbstract:
Giant HII regions contain large numbers of massive stars, and hence are expected to contain large numbers of SNRs. Until recently, however, only a few SNRs have been identified in extragalactic giant HII regions. Moreover, most of these SNRs are located at the outskirts of HII regions, instead of the core where most of the stars are located. The low detection rate and the outlying locations of the SNRs may be due to: 1) observational difficulties - the background HII regions are much more luminous than the SNRs in both optical line emission and radio continuum; 2) intrinsic invisibility of SNRs - stellar wind and SNRs may have created a supershell (Mac Low and McCray 1987), and the core of a giant HII region is filled with hot tenuous coronal gas; or 3) a genuine deficiency of supernovae and SNRs in the HII regions (Sramek and Weedman 1986).
4
Filipović, M. D., L. Staveley-Smith, W. Reid, and P. A. Jones. "Supernova Remnants in the Magellanic Clouds." Symposium - International Astronomical Union 218 (2004): 87–88. http://dx.doi.org/10.1017/s0074180900180672.
Full textAbstract:
A study of the nature and the spatial distribution of over 250 discrete radio sources (HII regions and SNRs) in the Magellanic Clouds (MCs) is underway. A multi-frequency comparison of these sources involves the latest radio, IR, optical and X-ray surveys with angular resolution of <1′. Special emphasis is given to the MC SNRs. Their morphology, birth rate and overall properties are investigated and compared with Galactic SNRs and SNRs from other nearby galaxies. Also, we are investigating the radio source distribution throughout both MCs.
5
Filipovic, M. D., P. A. Jones, and G. L. Vhite. "The relation between radio flux density and ionizing ultra-violet flux for HII regions and supernova remnants in the Large Magellanic cloud." Serbian Astronomical Journal, no. 166 (2003): 31–37. http://dx.doi.org/10.2298/saj0366031f.
Full textAbstract:
We present a comparison between the Parkes radio surveys (Filipovic et al 1995) and Vacuum Ultra-Violet (VUV) surveys (Smith et al. 1987) of the Large Magellanic Clouds (LMC). We have found 72 sources in common in the LMC which are known HII regions (52) and supernova remnants (SNRs) (19). Some of these radio sources are associated with two or more UV stellar associations. A comparison of the radio flux densities and ionizing UV flux for HII regions shows a very good correlation, as expected from theory. Many of the Magellanic Clouds (MCs) SNRs are embedded in HII regions, so there is also a relation between radio and UV which we attribute to the surrounding HII regions.
6
Odenwald, Sten F. "VLA Observations of Far-IR Sources Toward the Galactic Center." Symposium - International Astronomical Union 136 (1989): 205–11. http://dx.doi.org/10.1017/s0074180900186553.
Full textAbstract:
Preliminary results are presented from a 4.8-GHz VLA study of 5 far-IR sources within 1° of the Galactic center. Sgr-D and FIR-27 appear to be nearly featureless radio sources similar to young blister type HII regions, and FIR-21 has a filamentary structure similar to bright rimmed HII regions or Crab-like supernova remnants. Also presented are additional observations of Sgr-C.
7
Filipović, Miroslav D., Paul A. Jones, Graeme L. White, and Raymond F. Haynes. "Comparison of Discrete Sources in Radio and Hα Surveys of the Magellanic Clouds and the Potential for the New Hα Survey." Publications of the Astronomical Society of Australia 15, no. 1 (1998): 128–31. http://dx.doi.org/10.1071/as98128.
Full textAbstract:
AbstractWe present a comparison between the latest Parkes radio surveys (Filipović et al. 1995, 1996, 1997) and Hα surveys of the Magellanic Clouds (Kennicutt & Hodge 1986). We have found 180 discrete sources in common for the Large Magellanic Cloud (LMC) and 40 in the field of the Small Magellanic Cloud (SMC). Most of these sources (95%) are HII regions and supernova remnants (SNRs). A comparison of the radio and Hα flux densities shows a very good correlation and we note that many of the Magellanic Clouds SNRs are embedded in HII regions.
8
Turtle, A. J. "Supernova Remnants in the Magellanic Clouds Observed at the Molonglo Observatory." Symposium - International Astronomical Union 125 (1987): 130. http://dx.doi.org/10.1017/s0074180900160656.
Full textAbstract:
Radio surveys of the Magellanic Clouds at 843 MHz have been made with the Molonglo Observatory Synthesis Telescope. An initial catalogue (Mills et al. 1984) presented details of 38 supernova remnants detected by a combination of X-ray, optical and radio observations. The subsequent completion of the radio survey has revealed at least a further 17 remnants, mainly of large diameter and undetected by the Einstein X-ray Observatory. Though a few remnants have their radio emission concentrated towards their centre there is no evidence in the Magellanic Clouds for a Crab-like plerion (without an associated shell). The two well-established plerions 0540-693 (with optical and X-ray pulsar) and 0538-691 (N157B) appear to be connected with partial shells of strong radio emission which are relatively weak in optical emission lines (0538-691 is superposed on an HII region). Four sources which have a central concentration show larger optical and X-ray shells. The optical spectra of three of these (0505-679, 0509-675 and 0519-690) are dominated by the emission lines of hydrogen and Tuohy et al. (1982) argue that they are remnants of Type I supernovae. The fourth source (0453-685) which has detectable [OIII] emission may be an older but similar type of remnant. A further remnant 0509-687 (N103B) is compact but its radio diameter of 6 pc agrees with the published X-ray result.
9
Duncan, A. R., and R. F. Haynes. "Bright Prospects: Comparing the Hα Survey with Large-scale Radio Continuum Emission." Publications of the Astronomical Society of Australia 15, no. 1 (1998): 50–55. http://dx.doi.org/10.1071/as98050.
Full textAbstract:
AbstractProspects for comparisons between the AAO/UKST Hα survey and large-scale radio continuum emission are considered, with particular reference to the recently completed Parkes 2·4 GHz survey of the southern Galactic Plane. Both these surveys have a high sensitivity to thermal emission, and comparisons between the Parkes work and previous Hα surveys show many objects in common. Possibilities for new detections include: a number of new supernova remnants; the faint extensions and envelopes surrounding ‘classical’ HII complexes, and other faint regions of thermal emission; several active HII complexes, including an outflow of ionised gas from IC 4628 and a number of bi-polar ‘plumes’ of low-density, thermal material apparently associated with HII complexes on the Carina spiral arm.
10
Pedlar, Alan, Tom Muxlow, and Jon Riley. "Radio Observations of Supernova Remnants in the M82 Starburst." International Astronomical Union Colloquium 192 (2005): 219–25. http://dx.doi.org/10.1017/s0252921100009222.
Full textAbstract:
SummaryWe report on recent MERLIN, VLA and VLBI observations of the compact radio sources in the nearby starburst M82, with angular resolutions ranging from arcseconds to milliarcseconds. The spectral properties of the compact sources have been investigated by 15 GHz VLA-Pie Town observations which show that 16 of the less luminous compact sources are, in fact, HII regions. However the steep non-thermal spectrum, parsec size and small variability of the remaining sources is consistent with their being supernova remnants. Several show clear shell structures at MERLIN resolution (~50 mas) and 5 have been resolved further using VLBI. Measurements of the most compact source (41.95+575) shows an expansion velocity of ~ 2000 km s-1, and one of the best defined SNR shells (43.31+592) shows an expansion velocity of ~ 104 km s-1. Recent VLBI and MERLIN measurements confirm this expansion velocity and show little evidence for deceleration. We comment on the discrepancy between this measured expansion velocity and the low expansion velocities predicted theoretically for remnants in M82.
11
HAN, J. L., W. REICH, X. H. SUN, X. Y. GAO, L. XIAO, W. B. SHI, P. REICH, and R. WIELEBINSKI. "THE SINO-GERMAN λ6 CM POLARIZATION SURVEY OF THE GALACTIC PLANE: A SUMMARY." International Journal of Modern Physics: Conference Series 23 (January 2013): 82–91. http://dx.doi.org/10.1142/s2010194513011100.
Full textAbstract:
We have finished the λ6 cm polarization survey of the Galactic plane using the Urumqi 25 m radio telescope. It covers 10° ≤ l ≤ 230° in Galactic longitude and |b| ≤ 5° in Galactic latitude. The new polarization maps not only reveal new properties of the diffuse magnetized interstellar medium, but also are very useful for studying individual objects such as HII regions, which may act as Faraday screens with strong regular magnetic fields inside, and supernova remnants for their polarization properties and spectra. The high sensitivity of the survey enables us to discover two new SNRs G178.2–4.2 and G25.3–2.1 and a number of HII regions.
12
Aksaker, Nazim, Sinan K. Yerli, Ümit Kızıloğlu, and Betül Atalay. "Emission Lines of Northern Planetary Nebulae." Proceedings of the International Astronomical Union 12, S323 (October 2016): 333–34. http://dx.doi.org/10.1017/s1743921317001909.
Full textAbstract:
AbstractIn this work, we present results of long slit spectrophotometric emission line flux observations of selected planetary nebulae (PNe). We have measured absolute fluxes and equivalent widths (EW) of all observable emission lines. In addition to these observations, electron temperatures (Te), densities (Ne), and chemical abundances were also calculated. The main purpose of this work is to fill the gaps in emission line flux standards for the northern hemisphere. It is expected that the measured fluxes would be used as standard data set for further photometric and spectrometric measurements of HII regions, supernova remnants etc.
13
Montmerle, Thierry. "Massive Stars and Giant HII Regions: The High-Energy Picture." Symposium - International Astronomical Union 143 (1991): 397–408. http://dx.doi.org/10.1017/s0074180900045502.
Full textAbstract:
Giant HII regions contain highly energetic objects: luminous, massive stars (including Wolf-Rayet stars) generating powerful winds, as well as, often, supernova remnants. These objects interact with the surrounding gas by creating shock waves. Part of the energy input is radiated away in the form of X-rays; also, protons and electrons may be accelerated in situ and generate γ-rays by collisions with the ionized gas. In addition, the stars themselves (including the accompanying low-mass PMS stars) are sources of X-rays, and W-R stars may emit continuum y-rays and are associated with nuclear γ-ray lines seen in the interstellar medium. Therefore, both through the stars they contain and through interactions within the gas, giant HII regions are, in addition to their more traditional properties and over nearly 7 decades in energy, important sources of high-energy radiation.
14
Green, A. J. "The MOST Galactic Plane Survey." Publications of the Astronomical Society of Australia 14, no. 1 (1997): 73–76. http://dx.doi.org/10.1071/as97073.
Full textAbstract:
AbstractThe Molonglo Observatory Synthesis Telescope (MOST) has been upgraded to increase the diameter of the field of view from 70′ to 2·7°. A survey of the Galactic Plane is proposed to completely cover the region 240° ≤ l ≤ 365°, ∣ b ∣ ≤ 10° with a (1σ) sensitivity of 1–2 mJy. The results will provide a major resource for the investigation of supernova remnants, HII regions and transient radio sources. They will also be correlated with the galaxy search from the HI multibeam survey to be conducted at the Parkes telescope.
15
Reich, W. "Radio Studies of Cosmic Rays in the Galaxy." Symposium - International Astronomical Union 144 (1991): 187–96. http://dx.doi.org/10.1017/s0074180900089063.
Full textAbstract:
Changes of the cosmic ray electron spectrum throughout the Galaxy have been found, based on the comparison of large-scale radio continuum surveys. These observations are not compatible with the assumption of a static Galactic halo, but indicate the existence of a Galactic wind. Galactic plane surveys reveal sources of cosmic ray electrons in the Galactic disk. Recent studies of the population of radio sources show no evidence for a large number of compact Galactic non-thermal sources. Most of the extended sources are probably HII-regions. Relatively few new supernova remnants (SNRs) with low surface brightness could be identified. Most of the non-thermal emission in the disk-halo interface seems diffuse or unresolved, even at arcmin angular resolution.
16
Wielebinski, R. "Radio Continuum Surveys Of The Sky." Symposium - International Astronomical Union 133 (1988): 323–29. http://dx.doi.org/10.1017/s0074180900139774.
Full textAbstract:
Radio continuum surveys give us the fundamental information about the distribution of the radio intensity across the sky. The radio waves originate in three fundamental emitting processes and are measured superposed in the antenna beam. At the lowest radio frequencies (below 10 GHz) the nonthermal emission process (synchrotron radiation) predominates. This radio emission comes from supernova remnants, from the “galactic background” (relativistic electrons diffusing in galactic magnetic fields), but also from extragalactic objects (galaxies, quasars, radio galaxies, etc.). In the frequency range 10 GHz < f < 300 GHz the thermal (free-free) process becomes dominant. In the Galaxy we see the HII regions along the galactic plane. In nearby galaxies we can identify the thermal emission in the disks. Above 300 GHz the dust is seen. This is the boundary region between radio and far-infrared radiation.
17
Vukotic, B., I. Bojicic, T. G. Pannuti, and Dejan Urosevic. "A search for candidate radio supernova remnants in the nearby irregular starburst galaxies NGC 4214 and NGC 4395." Serbian Astronomical Journal, no. 170 (2005): 101–10. http://dx.doi.org/10.2298/saj0570101v.
Full textAbstract:
We present the results of a search for new candidate radio su?pernova remnants (SNRs) in the nearby starburst irregular galaxies NGC 4214 and NGC 4395 using archived radio observations made with the Very Large Array (VLA) at the wavelengths of 3.5 cm, 6 cm and 20 cm for NGC 4214 and 6 cm and 20 cm for NGC 4395. These observations were analyzed as part of our ongoing search for candidate radio SNRs in nearby galaxies: the goal of this search is to prepare a large sample of candidate radio SNRs for the purpose of a robust statistical study of the properties of these sources. Based on our analysis, we have confirmed the nonthermal nature of the discrete radio sources ? and ? in NGC 4214 and classify these sources as candidate radio SNRs based on their positional coincidences with HII regions in that galaxy. We have measured the flux densities of the two candidate radio SNRs at each wavelength and calculated corresponding spectral indices: we have also measured flux densities of two other discrete radio sources in these galaxies - ? in NGC 4214 and #3 in NGC 4395 which we suspect to be additional candidate radio SNRs based on their positional coincidences with other HII regions in these galaxies. However, the radio data presently available for these sources can?not confirm such a classification and additional observations are needed. We have also calculated the radio luminosities Lradio at the wavelength of 20 cm for these two candidate radio SNRs as well as the corresponding values for the minimum total energy Emin required to power these radio sources via synchrotron emission and the corresponding magnetic field strength Bmin. We have compared our mean calculated values for these properties with the mean values for populations of candidate radio SNRs in other starburst galaxies: while the values for Lradio and Bmin are roughly comparable to the values seen in other starburst galaxies, the mean value for Emin is higher than the mean value of any other starburst galaxy. Finally, we include these two candidate radio SNRs in a discussion of the ? ? D relation for extragalactic candidate radio SNRs and find that these sources are located on the shallower end of the master ? ? D relation for all extragalactic SNRs as derived by Urosevic et al.(2005). .
18
Rosado, Margarita, Etienne le Coarer, and Yvon Georgelin. "Results of the Hα Survey of the Small Magellanic Cloud." International Astronomical Union Colloquium 149 (1995): 150–54. http://dx.doi.org/10.1017/s0252921100022843.
Full textAbstract:
AbstractWe present the results of a kinematic survey of the Small Magellanic Cloud, performed with a scanning FP interferometer mainly at Hα. These data allow us to study the overall dynamics of the ionized hydrogen of this galaxy as well as the kinematics of classes of objects. In this presentation we exemplify how the availability of data in several wavelengths can be very useful in establishing the nature of large nebular complexes of the Small Magellanic Cloud. Our kinematic study allows us to discriminate faint shocked nebulae (such as supernova remnants) inside bright HII regions. This is confirmed by recently available radio and X-ray data.
19
Rosado, M., A. Bullejos, M. Valdez, L. Georgiev, C. Lacey, J. Borissova, and C. Esteban. "Kinematics of the Ionized Gas in the Irregular Galaxies IC 10 and NGC 4449." Symposium - International Astronomical Union 190 (1999): 168–70. http://dx.doi.org/10.1017/s0074180900117796.
Full textAbstract:
We have searched for supernova remnants (SNRs) in the irregular galaxies IC 10 and NGC 4449 by means of Fabry-Perot interferometry in Hα and [SII] lines, complemented by radio continuum observations. We find several new SNR candidates in each galaxy in addition to the known ones. Although these galaxies have several common properties, the distributions of SNRs in each galaxy is different. This shows that the star formation mechanisms in these galaxies act in different ways, in favor of the formation of a large nebular HII complex in IC 10, similar to 30 Dor in the Large Magellanic Cloud. We are studying the conditions over which these different star formation histories take place.
20
Sofue, Yoshiaki. "Dark Supernova Remnants Revealed by CO-Line Bubbles in the W43 Molecular Complex along the 4-kpc Galactic Arm." Galaxies 9, no. 1 (February 4, 2021): 13. http://dx.doi.org/10.3390/galaxies9010013.
Full textAbstract:
Fine structure of the density distribution in giant molecular clouds (GMCs) around W43 (G31+00+90 km s−1at ∼5.5 kpc) was analyzed using the FUGIN* CO-line survey at high-angular (20”∼0.5 pc) and velocity (1.3 km s−1) resolutions (*Four-receiver-system Unbiased Galactic Imaging survey with the Nobeyama 45-m telescope). The GMCs show highly turbulent structures, and the eddies are found to exhibit spherical bubble morphology appearing in narrow ranges of velocity channels. The bubbles are dark in radio continuum emission, unlike usual supernova remnants (SNR) or HII regions, and in infrared dust emission, unlike molecular bubbles around young stellar objects. The CO bubbles are interpreted as due to fully evolved buried SNRs in molecular clouds after rapid exhaustion of the released energy in dense molecular clouds. Then, the CO bubbles may be a direct evidence for exciting and maintaining the turbulence in GMCs by SN origin. Search for CO bubbles as “dark SNRs” (dSNR) will have implication to estimate the supernova rate more accurately, and hence the star formation activity in the Milky Way.
21
Sidorchuk, M. A., N. M. Vasilenko, O. M. Ulyanov, O. O. Konovalenko, D. V. Mukha, E. A. Abramenkov, K. M. Sidorchuk, and A. I. Miasoied. "50 YEARS OF RESEARCH IN CONTINUUM AT THE UTR-2 RADIO TELESCOPE." Radio physics and radio astronomy 26, no. 4 (November 24, 2021): 287–313. http://dx.doi.org/10.15407/rpra26.04.287.
Full textAbstract:
Purpose: The results of research in continuum decameter-wave radio emission of the Galaxy background, ionized hydrogen regions, supernova remnants, extragalactic discrete sources, extended galaxies, galactic clusters, extragalactic background are given. The aim of this work is reviewing the results achieved for over 50-years of the UTR-2 radiotelescope research of our Galaxy and its population, as well as extragalactic radio sources in the continuum radio emission spectrum at extremely low frequencies for the ground based observations. Design/methodology/approach: The review, analysis, collection of archival data in various publications related to the subjectof this work. Findings: The basic results of studying the ionized hydrogen regions, supernova remnants, Galaxy background emission and its large-scale structure are given, and the maps of these sources are obtained. The catalog of extragalactic discrete radio sources of the most Northern sky part and the cosmological conclusions based on its analysis are described; the estimate of the isotropic extragalactic background brightness temperature is obtained; for the first time, the observational results for the Andromeda galaxy and two galactic clusters Coma and A2255 are given briefly. Conclusions: All the results presented here emphasize the uniqueness and importance of research in the decameter wavelength range, and the large area, flexibility of structure, continuous improvement make the UTR-2 radio telescope an indispensable tool for solving the most important tasks of modern radio astronomy, despite its respectable age. For example, only in the range of 10 to 30 MHz the ionized part of the most common element in the universe, the hydrogen, becomes optically thick and begins to absorb the synchrotron emission on the line of sight, which allows rather easy separation of thermal and non-thermal components of radioemission. This property allows to determine the ionized hydrogen regions’ electron temperature and the electron concentration on the line of sight independently in studying the hydrogen emission regions. When studying the supernova remnants, we can determine the ionized matter location by their spectrum drops ‒ before, inside or behind the remnant. Based on the HB3 supernova remnant radio imagies, an assumption was made on the existence of an ionized hydrogen relic shell aroundit, being caused by the initial ultraviolet flash of a supernova. For the first time, the maps of the Northern sky large-scale structure in the declination range from ‒15° to +85° at extremely low frequencies 10, 12.6, 14.7, 16.7, 20 and 25 MHz for the ground-based observations are published, which, besides their own scientific value, may allow to correct the UTR-2 radio telescope imaging results. Using the full-resolution UTR-2 maps and the developed method of multifrequency T‒T diagrams, it was possible to separate the background radiation into galactic and extragalactic components and construct the spectrum of the latter. From the analysis of the most complete decameter wavelength range catalog of discrete sources, it follows that there is a gap in the redshift spatial distribution for all classes of extragalactic sources. The existence of an ionized hydrogen ring in the Andromeda Nebula disk has been suggested. It is shown that the main partof the galaxy clusters decameter-wave emission comes from haloes and relics. Key words: decameter range; discrete sources; supernovaremnants; catalog; continuum radio emission; HII regions; UTR-2; background emission
22
Greenhouse, Matthew A., Uri Feldman, Howard A. Smith, Marcel Klapisch, Anand K. Bhatia, and Avi Bar-Shalom. "Infrared Coronal Emission Lines and the Possibility of their Laser Emission in Seyfert Nuclei." Symposium - International Astronomical Union 159 (1994): 447. http://dx.doi.org/10.1017/s0074180900176284.
Full textAbstract:
Infrared coronal emission lines are providing a new window for observation and analysis of highly ionized gas in Galactic and extragalactic sources such as Seyfert nuclei and classical novae shells. These lines are expected to be primary coolants in colliding galaxies, galaxy cluster cooling flows, cometary-compact HII regions, and supernova remnants. In this poster, we summarize results discussed in detail by Greenhouse et al. 1993, ApJS, 88, 23. We discuss approximately 74 infrared (1 < λ μm < 280) transitions within the ground configurations 2s22pk and 3s23pk (k = 1 to 5) or the first excited configurations 2s2p and 3s3p of highly ionized (χ ≥ 100 eV) O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, and Ni. We present results from detailed balance calculations, critical densities for collisional de-excitation, intrinsic photon rates, branching ratios, and excitation temperatures for the transitions. The temperature and density parameter space for dominant cooling via infrared coronal lines is presented, and the relationship of infrared and optical coronal lines is discussed.
23
Lonsdale, Colin J., Katherine R. de Kleer, Philip J. Diamond, Hannah Thrall, Carol J. Lonsdale, and Harding E. Smith. "OH emission and absorption associated with supernovae in Arp 220." Proceedings of the International Astronomical Union 3, S242 (March 2007): 432–36. http://dx.doi.org/10.1017/s1743921307013555.
Full textAbstract:
AbstractWe present parsec-resolution spectral-line VLBI data for two epochs separated by 15 months as a precise new probe of the innermost regions of the nearby Ultraluminous Infrared Galaxy (ULIRG) Arp 220. This galaxy hosts a powerful starburst, with an associated supernova (SN) rate of order 4/yr. An extensive population of compact continuum sources interpreted as radio supernovae (RSNe) and young supernova remnants (SNR) has been imaged. We show here that many of the supernova-related radio continuum point sources exhibit clear evidence of OH absorption or maser emission in the intervening gas, and as such provide us with a sampling of conditions along very narrow and specific lines of sight through the nuclear environment. The OH gas along these lines of sight exhibits velocity dispersions of up to several tens of km/sec, and that in some cases, multiple distinct concentrations of masing gas at different radial velocities can be discerned. There is evidence for variability in the OH properties on ~1yr timescales. Our results are discussed in the context of the overall OH megamaser properties of Arp 220.
24
Hopp, Ulrich, H. U. Zimmermann, Manfred Stickel, and Christian Henkel. "A Supernova Remnant in the Dwarf HO IX." Symposium - International Astronomical Union 171 (1996): 392. http://dx.doi.org/10.1017/s0074180900233111.
Full textAbstract:
The dwarf irregular galaxy Ho IX (DDO 66) is a satellite of the giant spiral M81. Triggered by an interaction with M81 (Hopp & Schulte-Ladbeck, 1987 AA 187, 5), Ho IX may have recently undergone a burst of star formation. On very deep Calar Alto 3.5m telescope R images, we detected a ring-like nebula in the northeastern part of Ho IX, which is situated near to the giant CO molecular cloud recently discussed by Henkel et al. (1993 AA 273, L15). The structure of the nebula resembles supernova remnants like CTB 80. No HI-features can be detected at its location, especially no hole. It shows a blue central point source (R=21.7). A Lucy deconvolution of the 0.9″ seeing images indicates further faint point sources, perhaps a small stellar cluster. An optical long slit spectrum of the nebula shows emission lines with ratios as in old supernova remnants while it excludes normal HII regions, planetary nebula, or the LMC X-1 type nebula. The position of the central object coincides with a bright and variable ROSAT point source which was already detected by the Einstein spacecraft. The X-ray spectrum is rather steep and shows strong intrinsic absorption. The nature of the X-ray source and its possible connection to the optical nebula is not yet understood. Miller (1995, ApJ 446, L75) who independetly found the nebula interpretated his spectra as a supershell surrounding an OB association. Our optical nebula line ratios severely deviates from Miller's. Our ratios as the X-ray spectrum point more to a SNR at the M81 distance, most probably belonging to Ho IX.
25
Moorwood, A. F. M., and E. Oliva. "Infrared [FeII] and H2 Line Emission in Active Galactic Nuclei." Symposium - International Astronomical Union 134 (1989): 365–71. http://dx.doi.org/10.1017/s007418090014135x.
Full textAbstract:
Infrared spectra around [FeII](1.644μm), H2 (v = 1-0 S(1) at 2.121μm) and Brγ (H 7-4 at 2.167μm) have been obtained of 35 emission line nuclei whose optical spectra range from pure HII regionlike to Seyfert 1. All three emission lines have been detected in a large fraction of those nuclei exhibiting starburst activity but not in “pure” Seyferts. The highest detection frequency, however, was found for composite nuclei showing evidence for both starburst and Seyfert activity. Several arguments suggest that both the [FeII] and H2 are shock excited and could be largely attributed to supernova remnants. The fact that the [FeII]/Brγ and H2/Brγ ratios tend to be somewhat larger in composite than in pure starburst nuclei, however, plus significant spatial displacements between the [FeII] and H2 emitting regions found recently during follow-up observations of selected galaxies suggest that large scale phenomena, e.g. SN winds or mass outflows from AGN, may also be important.
26
Corbelli, Edvige, Jonathan Braine, and Fatemeh S. Tabatabaei. "Radio emission during the formation of stellar clusters in M 33." Astronomy & Astrophysics 639 (July 2020): A27. http://dx.doi.org/10.1051/0004-6361/202037555.
Full textAbstract:
Aims. We investigate thermal and nonthermal radio emission associated with the early formation and evolution phases of young stellar clusters (YSCs) selected by their mid-infrared (MIR) emission at 24 μm in M 33. We consider regions in their early formation period, which are compact and totally embedded in the molecular cloud, and in the more evolved and exposed phase. Methods. Thanks to recent radio continuum surveys between 1.4 and 6.3 GHz we are able to find radio source counterparts to more than 300 star forming regions of M 33. We identify the thermal free–free component for YSCs and their associated molecular complexes using the Hα line emission. Results. A cross-correlation of MIR and radio continuum is established from bright to very faint sources, with the MIR-to-radio emission ratio that shows a slow radial decline throughout the M 33 disk. We confirm the nature of candidate embedded sources by recovering the associated faint radio continuum luminosities. By selecting exposed YSCs with reliable Hα flux, we establish and discuss the tight relation between Hα and the total radio continuum at 5 GHz over four orders of magnitude. This holds for individual YSCs as well as for the giant molecular clouds hosting them, and allows us to calibrate the radio continuum–star formation rate relation at small scales. On average, about half of the radio emission at 5 GHz in YSCs is nonthermal with large scatter. For exposed but compact YSCs and their molecular clouds, the nonthermal radio continuum fraction increases with source brightness, while for large HII regions the nonthermal fraction is lower and shows no clear trend. This has been found for YSCs with and without identified supernova remnants and underlines the possible role of massive stars in triggering particle acceleration through winds and shocks: these particles diffuse throughout the native molecular cloud prior to cloud dispersal.
27
Hamza, Hasanein A., Ameerah Ab Al Sadooni, and Jacco Th van Loon. "Feedback from Ionized Outflows Traced Across the Nearly Edge-on Disk of the Nearby Seyfert 2 Galaxy NGC 4945*." NeuroQuantology 18, no. 12 (December 31, 2020): 06–17. http://dx.doi.org/10.14704/nq.2020.18.12.nq20232.
Full textAbstract:
The aim of this work is to understand the impact of ionized outflows from H II regions in the nearby Seyfert 2 galaxy NGC4945. The study is based on long-slit optical spectra obtained at the Southern African large Telescope (SALT). The analysis focussed on recombination lines (Hα and Hβ) and forbidden lines ([N II]λλ6549,6583, [S II]λλ 6717,6731 and [O III] λλ4959,5007). The physical properties of 26 emission-line objects were determined from a diagnostic diagram. They are found to represent different physical environments normally encountered in supernova remnants, planetary nebulae (PNe) and classical HII regions, with electron densities varying between 16–3000 cm-3. Apart from tracing the galactic rotation, in some cases the line profiles show broadening or even line splitting – we take this as evidence that these regions will have an impact (feedback) onto the surrounding interstellar medium. The presentday chemical abundances were determined using the strong lines method (O3N2 and N2 indices). The oxygen abundances are constant between galactocentric distances of ~ 1–5 kpc, while the nitrogen abundance increases outwards. Taken together with a tentative positive correlation between oxygen and nitrogen abundance, a generally high metallicity but lower in the nucleus than expected from a comparison with the Milky Way, we explain this in terms of the inside–out build-up of the disk and present-day nuclear activity triggered by the accretion of relatively metal-poor gas.
28
Rennie, Thomas J., Stuart E. Harper, Clive Dickinson, Liju Philip, Kieran A. Cleary, Richard J. Bond, Jowita Borowska, et al. "COMAP Early Science. VI. A First Look at the COMAP Galactic Plane Survey." Astrophysical Journal 933, no. 2 (July 1, 2022): 187. http://dx.doi.org/10.3847/1538-4357/ac63c8.
Full textAbstract:
Abstract We present early results from the CO Mapping Array Project (COMAP) Galactic Plane Survey conducted between 2019 June and 2021 April, spanning 20° < ℓ < 40° in Galactic longitude and ∣b∣ < 1.°5 in Galactic latitude with an angular resolution of 4.′5. We present initial results from the first part of the survey, including the diffuse emission and spectral energy distributions of H ii regions and supernova remnants (SNRs). Using low- and high-frequency surveys to constrain free–free and thermal dust emission contributions, we find evidence of excess flux density at 30 GHz in six regions, which we interpret as anomalous microwave emission. Furthermore we model ultracompact H ii contributions using data from the 5 GHz CORNISH catalog and reject these as the cause of the 30 GHz excess. Six known SNRs are detected at 30 GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at 30 GHz is consistent with a power-law extrapolation from lower frequencies with no indication of spectral steepening in contrast with recent results from the Sardinia Radio Telescope. We also extract five hydrogen radio recombination lines (RRLs) to map the warm ionized gas, which can be used to estimate electron temperatures or to constrain continuum free–free emission. The full COMAP Galactic Plane Survey, to be released in 2023/2024, will span ℓ ∼ 20°–220° and will be the first large-scale radio continuum and RRL survey at 30 GHz with 4.′5 resolution.