The Nature of the Radio Sources within the Cepheus A Star-forming Region

1996 ◽  
Vol 459 ◽  
pp. 193 ◽  
Author(s):  
Guido Garay ◽  
Solange Ramirez ◽  
Luis F. Rodriguez ◽  
Salvador Curiel ◽  
Jose M. Torrelles
Keyword(s):  
Radio Sources ◽  
Star Forming ◽  
Cepheus A

scholarly journals VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz

2018 ◽  
Vol 616 ◽  
pp. A128 ◽  
Author(s):  
N. Herrera Ruiz ◽  
E. Middelberg ◽  
A. Deller ◽  
V. Smolčić ◽  
R. P. Norris ◽  
...  
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Lower Limit ◽  
High Sensitivity ◽  
Host Galaxy ◽  
Radio Sources ◽  
Source Population ◽  
Star Forming ◽  
Brightness Temperatures ◽  
Long Baseline

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of μJy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, meaning that it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compact and have large brightness temperatures, and therefore they are most likely AGN (when the host galaxy is located at z ≥ 0.1). On the other hand, this technique only allows us to positively identify when a radio-active AGN is present, in other words, we cannot affirm that there is no AGN when the source is not detected. For this reason, the number of identified AGN using VLBI should be always treated as a lower limit. We present a catalogue containing the 35 radio sources detected with the VLBA+GBT, ten of which were not previously detected using only the VLBA. We have constructed the radio source counts at 1.4 GHz using the samples of the VLBA and VLBA+GBT detected sources of the COSMOS field to determine a lower limit for the AGN contribution to the faint radio source population. We found an AGN contribution of >40−75% at flux density levels between 150 μJy and 1 mJy. This flux density range is characterised by the upturn of the Euclidean-normalised radio source counts, which implies a contribution of a new population. This result supports the idea that the sub-mJy radio population is composed of a significant fraction of radio-emitting AGN, rather than solely by star-forming galaxies, in agreement with previous studies.

scholarly journals VSOP, A Space VLBI Programme

1990 ◽  
Vol 123 ◽  
pp. 263-269
Author(s):  
H. Hirabayashi
Keyword(s):  
Active Galactic Nuclei ◽  
Phase Transfer ◽  
Galactic Nuclei ◽  
Satellite Orbit ◽  
Radio Sources ◽  
Space Observatory ◽  
Stellar Objects ◽  
Radio Observatory ◽  
Star Forming ◽  
Star Forming Regions

AbstractVSOP, VLBI Space Observatory Programme, is an approved space VLBI programme of ISAS for the study of very compact radio sources with the synthesized aperture of 30,000 km diameter, by connecting an orbiting radio observatory with ground radiotelescopes. The VSOP satellite carrying 10 m antenna with 1.6, 5, and 22 GHz band receivers will be launched in early 1995 by M-V rocket of ISAS into an eccentric orbit with 20,000 km in apogee height. The tracking network will be formed for the satellite orbit determination, phase transfer and IF down-link. VSOP aims imaging capability with best resolution of 0.0001 arc second in 22 GHz band. Imaging of active galactic nuclei, star forming regions and stellar objects, and radioastrometry are main scientific targets.

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 STATISTICAL ANALYSIS OF WATER MASERS IN STAR-FORMING REGIONS: CEPHEUS A AND W75 N

2010 ◽  
Vol 715 (1) ◽  
pp. 132-142 ◽  
Author(s):  
L. Uscanga ◽  
J. Cantó ◽  
J. F. Gómez ◽  
G. Anglada ◽  
J. M. Torrelles ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Star Forming ◽  
Star Forming Regions ◽  
Water Masers ◽  
Cepheus A

scholarly journals Radio Sources in the 2dF Galaxy Redshift Survey I. Radio Source Populations

1999 ◽  
Vol 16 (3) ◽  
pp. 247-256 ◽  
Author(s):  
Elaine M. Sadler ◽  
V. J. McIntyre ◽  
C. A. Jackson ◽  
R. D. Cannon
Keyword(s):  
Radio Galaxy ◽  
Radio Continuum ◽  
Radio Sources ◽  
Star Forming ◽  
Sky Survey ◽  
Homogeneous Set ◽  
First Results ◽  
Redshift Survey ◽  
Galaxy Redshift ◽  
Source Populations

AbstractWe present the first results from a study of the radio continuum properties of galaxies in the 2dF Galaxy Redshift Survey, (2dFGRS) based on thirty 2dF fields covering a total area of about 100 deg2. About 1·5% of galaxies with bJ < 19·4 mag. are detected as radio continuum sources in the NRAO VLA Sky Survey (NVSS). Of these, roughly 40% are star-forming galaxies and 60% are active galaxies (mostly low-power radio galaxies and a few Seyferts). The combination of 2dFGRS and NVSS will eventually yield a homogeneous set of around 4000 radio-galaxy spectra, which will be a powerful tool for studying the distribution and evolution of both AGN and starburst galaxies out to z ∼ 0·3.

scholarly journals Radio sources in the 2dF Galaxy Redshift Survey - II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz

2002 ◽  
Vol 329 (1) ◽  
pp. 227-245 ◽  
Author(s):  
Elaine M. Sadler ◽  
Carole A. Jackson ◽  
Russell D. Cannon ◽  
Vincent J. McIntyre ◽  
Tara Murphy ◽  
...  
Keyword(s):  
Radio Sources ◽  
Radio Luminosity ◽  
Star Forming ◽  
Luminosity Functions ◽  
Redshift Survey ◽  
Galaxy Redshift ◽  
Local Radio

scholarly journals FIGARO simulation: FIlaments & GAlactic RadiO simulation

2021 ◽  
Vol 38 ◽  
Author(s):  
Torrance Hodgson ◽  
Franco Vazza ◽  
Melanie Johnston-Hollitt ◽  
Benjamin McKinley
Keyword(s):  
Cross Correlation ◽  
Radio Sources ◽  
Dark Matter Halos ◽  
Frequency Range ◽  
Extragalactic Radio Sources ◽  
Star Forming ◽  
Public Resource ◽  
Magnetohydrodynamic Simulation ◽  
Relic Population ◽  
Galactic Radio

Abstract We produce the first low to mid-frequency radio simulation that incorporates both traditional extragalactic radio sources as well as synchrotron cosmic web emission. The FIlaments & GAlactic RadiO (FIGARO) simulation includes 10 unique 4° × 4° fields, incorporating active galactic nucleii (AGNs), star-forming galaxies (SFGs), and synchrotron cosmic web emission out to a redshift of z = 0.8 and over the frequency range 100–1 400 MHz. To do this, the simulation brings together a recent 1003 Mpc3 magnetohydrodynamic simulation (Vazza et al. 2019, A&A, 627, A5), calibrated to match observed radio relic population statistics, alongside updated ‘T-RECS’ code for simulating extragalactic radio sources (Bonaldi et al. 2019, MNRAS, 482, 2). Uniquely, the AGNs and SFGs are populated and positioned in accordance with the underlying matter density of the cosmological simulation. In this way, the simulation provides an accurate understanding of the apparent morphology, angular scales, and brightness of the cosmic web as well as—crucially—the clustering properties of the cosmic web with respect to the embedded extragalactic radio population. We find that the synchrotron cosmic web does not closely trace the underlying mass distribution of the cosmic web, but is instead dominated by shocked shells of emission surrounding dark matter halos and resembles a large, undetected population of radio relics. We also show that, with accurate kernels, the cosmic web radio emission is clearly detectable by cross-correlation techniques and this signal is separable from the embedded extragalactic radio population. We offer the simulation as a public resource towards the development of techniques for detecting and measuring the synchrotron cosmic web.

scholarly journals Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

2015 ◽  
Vol 585 ◽  
pp. A45 ◽  
Author(s):  
A. Gusdorf ◽  
R. Güsten ◽  
K. M. Menten ◽  
D. R. Flower ◽  
G. Pineau des Forêts ◽  
...  
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Shock Models ◽  
Cepheus A
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