Radio Continuum Emission from Sculptor Galaxies

1986 ◽  
Vol 6 (3) ◽  
pp. 325-329 ◽  
Author(s):  
J . I. Harnet
Keyword(s):  
Radio Emission ◽  
Blue Light ◽  
Hii Regions ◽  
Radio Continuum ◽  
Radial Dependence ◽  
Continuum Emission ◽  
Upper Limits ◽  
Peak Flux

AbstractThe five major members of the Sculptor Group of galaxies and NGC 45 have been observed with the Molonglo observatory synthesis telescope. NGC 247 and NGC 300 were not detected and upper limits to their 843 MHz flux densities are given. Radio emission from NGC 7793 is discussed with particular attention to its morphology, radial dependence compared with that of the blue light and possible coincidences between HII regions and 843 MHz peak flux densities.

scholarly journals Radio Continuum Emission from the Nuclei of Normal Galaxies

1980 ◽  
Vol 5 ◽  
pp. 177-184 ◽  
Author(s):  
J. M. van der Hulst
Keyword(s):  
Radio Emission ◽  
Galactic Center ◽  
Galactic Nuclei ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Thermal Source ◽  
Very Large Array ◽  
Normal Galaxies ◽  
The Galaxy ◽  
Sgr A

During the last few years detailed and sensitive observations of the radio emission from the nuclei of many normal spiral galaxies has become available. Observations from the Very Large Array (VLA) of the National Radio Astronomy Observatory (NRAO1), in particular, enable us to distinguish details on a scale of ≤100 pc for galaxies at distances less than 21 Mpc. The best studied nucleus, however, still is the center of our own Galaxy (see Oort 1977 and references therein). Its radio structure is complex. It consists of an extended non-thermal component 200 × 70 pc in size, with embedded therein several giant HII regions and the central source Sgr A (˜9 pc in size). Sgr A itself consists of a thermal source, Sgr A West, located at the center of the Galaxy, and a weaker, non-thermal source, Sgr A East. Sgr A West moreover contains a weak, extremely compact (≤10 AU) source. The radio morphology of several other galactic nuclei is quite similar to that of the Galactic Center, as will be discussed in section 2. Recent reviews of the radio properties of the nuclei of normal galaxies have been given by Ekers (1978a,b) and De Bruyn (1978). The latter author, however, concentrates on galaxies with either active nuclei or an unusual radio morphology. In this paper I will describe recent results from the Westerbork Synthesis Radio Telescope (WSRT, Hummel 1979), the NRAO 3-element interferometer (Carlson, 1977; Condon and Dressel 1978), and the VLA (Heckman et al., 1979; Van der Hulst et al., 1979). I will discuss the nuclear radio morphology in section 2, the luminosities in section 3, and the spectra in section 4. In section 5 I will briefly comment upon the possible implications for the physical processes in the nuclei that are responsible for the radio emission.

scholarly journals A closer look at the deep radio sky: Multi-component radio sources at 3 GHz VLA-COSMOS

2019 ◽  
Vol 627 ◽  
pp. A142
Author(s):  
E. Vardoulaki ◽  
E. F. Jiménez Andrade ◽  
A. Karim ◽  
M. Novak ◽  
S. K. Leslie ◽  
...  
Keyword(s):  
Radio Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Radio Sources ◽  
Source Population ◽  
Data Set ◽  
Star Forming ◽  
Large Project ◽  
Automatic Code

Context. Given the unprecedented depth achieved in current large radio surveys, we are starting to probe populations of radio sources that have not been studied in the past. However, identifying and categorising these objects, differing in size, shape and physical properties, is becoming a more difficult task. Aims. In this data paper we present and characterise the multi-component radio sources identified in the VLA-COSMOS Large Project at 3 GHz (0.75 arcsec resolution, 2.3 μJy beam−1 rms), i.e. the radio sources which are composed of two or more radio blobs. Methods. The classification of objects into multi-components was done by visual inspection of 351 of the brightest and most extended blobs from a sample of 10,899 blobs identified by the automatic code BLOBCAT. For that purpose we used multi-wavelength information of the field, such as the 1.4 GHz VLA-COSMOS data and the Ultra Deep Survey with the VISTA telescope (UltraVISTA) stacked mosaic available for COSMOS. Results. We have identified 67 multi-component radio sources at 3 GHz: 58 sources with active galactic nucleus (AGN) powered radio emission and nine star-forming galaxies. We report eight new detections that were not observed by the VLA-COSMOS Large Project at 1.4 GHz, due to the slightly larger area coverage at 3 GHz. The increased spatial resolution of 0.75 arcsec has allowed us to resolve (and isolate) multiple emission peaks of 28 extended radio sources not identified in the 1.4 GHz VLA-COSMOS map. We report the multi-frequency flux densities (324 MHz, 325 MHz, 1.4 GHz & 3 GHz), star formation rates, and stellar masses of these objects. We find that multi-component objects at 3 GHz VLA-COSMOS inhabit mainly massive galaxies (> 1010.5 M⊙). The majority of the multi-component AGN lie below the main sequence of star-forming galaxies (SFGs), in the green valley and the quiescent region. Furthermore, we provide detailed descriptions of the objects and find that amongst the AGN there are two head-tail, ten core-lobe, nine wide-angle-tail (WAT), eight double-double or Z-/X-shaped, three bent-tail radio sources, and 26 symmetric sources, while amongst the SFGs we find the only star-forming ring seen in radio emission in COSMOS. Additionally, we report a large number (32 out of 58) of disturbed/bent multi-component AGN, 18 of which do not lie within X-ray groups in COSMOS (redshift range 0.08 ≤ z <  1.53). Conclusion. The high angular resolution and sensitivity of the 3 GHz VLA-COSMOS data set give us the opportunity to identify peculiar radio structures and sub-structures of multi-component objects, and relate them to physical phenomena such as AGN or star-forming galaxies. This study illustrates the complexity of the μJy radio-source population; at the sensitivity and resolution of 3 GHz VLA-COSMOS, the radio structures of AGN and SFG both emitting radio continuum emission, become comparable in the absence of clear, symmetrical jets. Thus, disentangling the AGN and SFG contributions using solely radio observations can be misleading in a number of cases. This has implications for future surveys, such as those done by square kilometre array (SKA) and precursors, which will identify hundreds of thousands of multi-component objects.

scholarly journals Radio Continuum Spectra of Planetary Nebulae

Galaxies ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 6
Author(s):  
Marcin Hajduk ◽  
Peter van Hoof ◽  
Karolina Sniadkowska ◽  
Andrzej Krankowski ◽  
Leszek Błaszkiewicz ◽  
...  
Keyword(s):  
Radio Emission ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Physical Parameters ◽  
Spectral Indices ◽  
Homogeneous Sphere ◽  
Spherical Morphology ◽  
Competing Models ◽  
Source Of Information

Radio continuum emission of planetary nebulae is a rich source of information about their structure and physical parameters. Although radio emission is well studied, planetary nebulae show higher spectral indices than expected for homogeneous sphere. A few competing models exist in the literature to explain this discrepancy. We propose that it is related to non-spherical morphology of most of planetary nebulae.

scholarly journals VLA Search for Optically Thick H II Regions in Luminous Embedded Infrared Sources

1987 ◽  
Vol 115 ◽  
pp. 185-186
Author(s):  
Paul T.P. Ho ◽  
T. N. Rengarajan
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
High Sensitivity ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Upper Limit ◽  
Infrared Sources ◽  
Sensitivity Maps

We have searched for radio continuum emission at 15 GHz from a number of deeply embedded protostar like infrared objects, using the B configuration of the VLA. The aim was to get high resolution (1″) and high sensitivity maps. For 10 objects (NGC 7538-IRS 3, GL 989, GL 4029-IRS 1, GL 437N, GL 2789, NGC 1333-IRS 13, S235B, GL 4029-IRS 2, R Mon and OMC2-IRS 3) we did not detect radio emission, the 3 upper limit being 0.3 – 0.5 mJy. Positive detections were made for W33A, 0MC2-IRS 4, S 235-IRS 1 and NGC 6334V-IRS 4. The cleaned maps for these objects are shown in Figures 1-4.

scholarly journals Radio continuum emission from HII regions in the Magellanic Clouds

1964 ◽  
Vol 20 ◽  
pp. 283-289 ◽  
Author(s):  
D. S. Mathewson ◽  
J. R. Healey
Keyword(s):  
Hii Regions ◽  
Magellanic Clouds ◽  
Radio Continuum ◽  
Optical Observations ◽  
Optical Data ◽  
Continuum Emission ◽  
Considerable Proportion ◽  
Galactic Emission ◽  
The Galaxy ◽  
Thermal Origin

A considerable proportion of the radio emission at high frequencies from the Galaxy is of thermal origin. This thermal radiation appears to originate both in very extended regions and in discrete sources. It has always been difficult to compare the radio and optical data for these HII regions as galactic optical observations are hampered by heavy obscuration. However, the HII regions in the Magellanic Clouds are relatively free from obscuration, and spectrophotometry by Dickel, Aller, and Faulkner (this volume, paper 63) and Henize (1956) have provided very good measurements of Hβ and Hα flux densities and the relative intensities of the OII, OIII lines. Also the distance to the Clouds is fairly well known (about 55 kpc) so that the linear dimensions of the HII regions may be estimated with some degree of accuracy in contrast to the galactic emission nebulae.

scholarly journals A VLA Survey of Late-time Radio Emission from Superluminous Supernovae and the Host Galaxies

2021 ◽  
Vol 922 (1) ◽  
pp. 17
Author(s):  
Bunyo Hatsukade ◽  
Nozomu Tominaga ◽  
Tomoki Morokuma ◽  
Kana Morokuma-Matsui ◽  
Yuichi Matsuda ◽  
...  
Keyword(s):  
Star Formation ◽  
Radio Emission ◽  
Current Data ◽  
Radio Continuum ◽  
Time Variability ◽  
Late Time ◽  
Type I ◽  
Host Galaxies ◽  
Very Large Array ◽  
Upper Limits

Abstract We present the results of 3 GHz radio continuum observations of 23 superluminous supernovae (SLSNe) and their host galaxies by using the Karl G. Jansky Very Large Array conducted 5–21 yr after the explosions. The sample consists of 15 Type I and 8 Type II SLSNe at z < 0.3, providing one of the largest samples of SLSNe with late-time radio data. We detected radio emission from one SLSN (PTF10hgi) and five hosts with a significance of >5σ. No time variability is found in late-time radio light curves of the radio-detected sources in a timescale of years except for PTF10hgi, whose variability is reported in a separate study. Comparison of star formation rates (SFRs) derived from the 3 GHz flux densities with those derived from SED modeling based on UV–NIR data shows that four hosts have an excess of radio SFRs, suggesting obscured star formation. Upper limits for undetected hosts and stacked results show that the majority of the SLSN hosts do not have a significant obscured star formation. By using the 3 GHz upper limits, we constrain the parameters for afterglows arising from interaction between initially off-axis jets and circumstellar medium (CSM). We found that the models with higher energies (E iso ≳ several × 1053 erg) and CSM densities (n ≳ 0.01 cm−3) are excluded, but lower energies or CSM densities are not excluded with the current data. We also constrained the models of pulsar wind nebulae powered by a newly born magnetar for a subsample of SLSNe with model predictions in the literature.

scholarly journals Circumstellar radio emission from pre-main sequence stars

1987 ◽  
Vol 122 ◽  
pp. 63-64
Author(s):  
Alexander Brown
Keyword(s):  
Radio Emission ◽  
Main Sequence ◽  
Radio Continuum ◽  
Circumstellar Envelopes ◽  
Main Sequence Stars ◽  
Radio Jets ◽  
Extended Radio ◽  
Upper Limits ◽  
Infra Red ◽  
Pms Stars

VLA radio continuum observations have been obtained for a number of pre-main sequence (PMS) stars in Corona Australis, Lupus, Scorpius and Taurus. A variety of PMS sources were detected and for other stars upper limits to the ionized mass loss rates were determined. A strong double source, showing two radio jets, was found associated with an embedded infra-red source in the R CrA molecular cloud. Some of the PMS stars show extended radio emission associated with ionized circumstellar envelopes, even though photoionization by EUV photons is not sufficient to produce the ionized regions.

scholarly journals Non-thermal radio emission from Wolf-Rayet stars

1999 ◽  
Vol 193 ◽  
pp. 59-60
Author(s):  
Jessica M. Chapman ◽  
Claus Leitherer ◽  
Bärbel Koribalski
Keyword(s):  
Radio Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
The Sun ◽  
Limited Sample ◽  
Thermal Radio ◽  
Thermal Radio Emission ◽  
Compact Array

We have used the Australia Telescope Compact Array to search for radio continuum emission at λ 3, 6, 13 and 20 cm from a distance-limited sample of 36 southern Wolf-Rayet stars within 3 kpc of the Sun. The observations were taken between 1994 and 1997. Radio continuum emission has been detected from 16 sources at 3 cm. Of these 11 sources were detected at 6 cm, seven sources were detected at 13 cm and 2 sources were detected at 20 cm (Chapman et al. 1999).

scholarly journals Observations of radio continuum emission from M31

1970 ◽  
Vol 38 ◽  
pp. 72-72
Author(s):  
G. G. Pooley
Keyword(s):  
Radio Emission ◽  
Major Axis ◽  
Radio Continuum ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Nuclear Region ◽  
Spiral Arms ◽  
Compact Source ◽  
M 31 ◽  
Sgr A

Observations of continuum emission from M 31 have been made with the Cambridge One-mile radio telescope (Pooley, 1969). Two observing frequencies were used; maps of the whole of the visible nebula were obtained at 408 MHz, and spectral data for the central region at 1407 MHz. The results show that the radiation from the disc is confined to the nucleus and to the population I spiral arms.The nuclear region may be described in terms of two spherical radio components, with diameters of 200 pc and 1 kpc. Any more compact source at the nucleus has a luminosity less than 1/20 of that of the source Sgr A in our Galaxy.The intensity of the radio emission from the spiral arms is closely correlated with the number of H ii regions visible. The main spiral arms, corresponding to Baade's arms 4 and 5, cross the major axis at about 8 and 12.5 kpc from the nucleus. The spectrum of the radiation shows that it is non-thermal in origin; the spectral index is 0.8. The intensity is less than that which would be observed from our own Galaxy at the same distance.

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