scholarly journals Search for radio emission from the exoplanets Qatar-1b and WASP-80b near 150 MHz using the giant metrewave radio telescope

2020 ◽  
Vol 500 (1) ◽  
pp. 211-214
Author(s):  
D A Green ◽  
N Madhusudhan
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Radio Telescope ◽  
Magnetic Moments ◽  
Wide Field ◽  
Extragalactic Radio Source ◽  
Field Surveys ◽  
Very Large Array ◽  
Sky Survey ◽  
Cross Match

ABSTRACT We present radio observations made towards the exoplanets Qatar-1b and WASP-80b near 150 MHz with the Giant Meterwave Radio Telescope (GMRT). These targets are relatively nearby irradiated giant exoplanets, a hot Jupiter and a hot Saturn, with sizes comparable to Jupiter but different masses and lower densities. Both the targets are expected to host extended H/He envelopes like Jupiter, with comparable or larger magnetic moments. No radio emission was detected from these exoplanets, with 3σ limits of 5.9 and 5.2 mJy for Qatar-1b and WASP-80b, respectively, from these targeted observations. These are considerably deeper limits than those available for exoplanets from wide-field surveys at similar frequencies. We also present archival Very Large Array (VLA) observations of a previously reported radio source close to 61 Vir (which has three exoplanets). The VLA observations resolve the source, which we identify as an extragalactic radio source, i.e. a chance association with 61 Vir. Additionally, we cross-match a recent exoplanet catalogue with the TIFR GMRT Sky Survey ADR1 radio catalogue, but do not find any convincing associations.

scholarly journals Cosmic dance in the Shapley Concentration Core

2018 ◽  
Vol 620 ◽  
pp. A25
Author(s):  
G. Di Gennaro ◽  
T. Venturi ◽  
D. Dallacasa ◽  
S. Giacintucci ◽  
P. Merluzzi ◽  
...  
Keyword(s):  
Radio Emission ◽  
Galaxy Clusters ◽  
Radio Galaxies ◽  
Wide Field ◽  
Host Galaxies ◽  
Very Large Array ◽  
Cluster Complexes ◽  
Dynamical State ◽  
Sky Survey ◽  
Radio Band

Context. The Shapley Concentration (⟨z⟩ ≈ 0.048) covers several degrees in the southern hemisphere, and includes galaxy clusters in advanced evolutionary stages, groups of clusters in the very early stages of merger, fairly massive clusters with ongoing accretion activity, and smaller groups located in filaments in the regions between the main clusters. Aims. With the goal to investigate the role of cluster mergers and accretion on the radio galaxy population, we performed a multi-wavelength study of the brightest cluster galaxies (BCGs) and of the galaxies showing extended radio emission in the cluster complexes of Abell 3528 and Abell 3558. In total, our study is based on a sample of 12 galaxies. Methods. We observed the clusters with the Giant Metrewave Radio Telescope (GMRT) at 235, 325, and 610 MHz, and with the Very Large Array (VLA) at 8.46 GHz. We complemented our study with the TIFR GMRT Sky Survey (TGSS) at 150 MHz, the Sydney University Molonglo Sky Survey (SUMSS) at 843 MHz, and the Australia Telescope Compact array (ATCA) at 1380, 1400, 2380, and 4790 MHz data. Finally, optical imaging with the VLT Survey Telescope (VST) is also available for the host galaxies as well as the mid-infrared coverage with the Wide-Field Infrared Survey Explorer (WISE). Results. We found significant differences in the properties of the radio emission of the BCGs in the two cluster complexes. The BCGs in the A 3528 complex and in A 3556, which are relaxed cool-core objects, are powerful active radio galaxies. They also present hints of restarted activity. On the contrary, the BCGs in A 3558 and A 3562, which are well-known merging systems, are very faint, or quiet, in the radio band. The optical and infrared properties of the galaxies, on the other hand, are fairly similar in the two complexes, showing all passive red galaxies. Conclusions. Our study shows remarkable differences in the radio properties of the BGCs, which we relate to the different dynamical state of the host cluster. On the contrary, the lack of changes between such different environments in the optical band suggests that the dynamical state of galaxy clusters does not affect the optical counterparts of the radio galaxies, at least over the lifetime of the radio emission.

scholarly journals YSTAR: Yonsei Survey Telescopes for Astronomical Research

2001 ◽  
Vol 183 ◽  
pp. 83-87
Author(s):  
Yong-Ik Byun ◽  
Won-Yong Han ◽  
Yong-Woo Kang ◽  
Moo-Young Chun ◽  
Sung-Yeol Yu ◽  
...  
Keyword(s):  
South Africa ◽  
Variable Stars ◽  
Primary Objective ◽  
Wide Field ◽  
Target Acquisition ◽  
Data Set ◽  
Field Surveys ◽  
Sky Survey ◽  
Two Factors ◽  
Astronomical Research

AbstractThe YSTAR program is a general sky survey looking for variability. The main equipments are three 0.5-m telescopes. These telescopes have fast F/2 optics covering nearly 3.5 square degree field onto a 2K CCD. They also have very fast slew capability, which exceeds 10 degrees per second. These two factors make them most suitable for rapid target acquisition and wide-field surveys of various kinds. Our primary objective is to identify and monitor variable stars down to 18th R-magnitude, and our observing mode allows the same data set to be also useful in identifying asteroids. Our first telescope has just begun regular automated operation, and the second telescope will be installed in South Africa within this year to provide coverage of the southern sky.

scholarly journals The optical luminosity function of LOFAR radio-selected quasars at 1.4 ≤ z ≤ 5.0 in the NDWFS-Boötes field

2020 ◽  
Vol 636 ◽  
pp. A12
Author(s):  
E. Retana-Montenegro ◽  
H. J. A. Röttgering
Keyword(s):  
Radio Emission ◽  
Luminosity Function ◽  
Field Survey ◽  
Sloan Digital Sky Survey ◽  
Spatial Density ◽  
Spectral Energy ◽  
Wide Field ◽  
Infrared Photometry ◽  
Mid Infrared ◽  
Sky Survey

We present an estimate of the optical luminosity function (OLF) of LOFAR radio-selected quasars (RSQs) at 1.4 <  z <  5.0 in the 9.3 deg2 NOAO Deep Wide-field survey (NDWFS) of the Boötes field. The selection was based on optical and mid-infrared photometry used to train three different machine learning (ML) algorithms (Random forest, SVM, Bootstrap aggregation). Objects taken as quasars by the ML algorithms are required to be detected at ≥5σ significance in deep radio maps to be classified as candidate quasars. The optical imaging came from the Sloan Digital Sky Survey and the Pan-STARRS1 3π survey; mid-infrared photometry was taken from the Spitzer Deep, Wide-Field Survey; and radio data was obtained from deep LOFAR imaging of the NDWFS-Boötes field. The requirement of a 5σ LOFAR detection allowed us to reduce the stellar contamination in our sample by two orders of magnitude. The sample comprises 130 objects, including both photometrically selected candidate quasars (47) and spectroscopically confirmed quasars (83). The spectral energy distributions calculated using deep photometry available for the NDWFS-Boötes field confirm the validity of the photometrically selected quasars using the ML algorithms as robust candidate quasars. The depth of our LOFAR observations allowed us to detect the radio-emission of quasars that would be otherwise classified as radio-quiet. Around 65% of the quasars in the sample are fainter than M1450 = −24.0, a regime where the OLF of quasars selected through their radio emission, has not been investigated in detail. It has been demonstrated that in cases where mid-infrared wedge-based AGN selection is not possible due to a lack of appropriate data, the selection of quasars using ML algorithms trained with optical and infrared photometry in combination with LOFAR data provides an excellent approach for obtaining samples of quasars. The OLF of RSQs can be described by pure luminosity evolution at z <  2.4, and a combined luminosity and density evolution at z >  2.4. The faint-end slope, α, becomes steeper with increasing redshift. This trend is consistent with previous studies of faint quasars (M1450 ≤ −22.0). We demonstrate that RSQs show an evolution that is very similar to that exhibited by faint quasars. By comparing the spatial density of RSQs with that of the total (radio-detected plus radio-undetected) faint quasar population at similar redshifts, we find that RSQs may compose up to ∼20% of the whole faint quasar population. This fraction, within uncertainties, is constant with redshift. Finally, we discuss how the compactness of the RSQs radio-morphologies and their steep spectral indices could provide valuable insights into how quasar and radio activity are triggered in these systems.

Infrared Surveys Planned for ASTRO-F

2005 ◽  
Vol 216 ◽  
pp. 347-352
Author(s):  
Hiroshi Shibai
Keyword(s):  
Far Infrared ◽  
Wide Field ◽  
Wavelength Band ◽  
Mid Infrared ◽  
Field Surveys ◽  
Infrared Wavelength ◽  
Sky Surveys ◽  
Sky Survey ◽  
Infrared Surveys ◽  
Higher Sensitivity

The next survey mission, ASTRO-F, is scheduled for launch in 2005. This is the first Japanese satellite dedicated to infrared astronomy. The primary purpose of this project is to investigate the birth and evolution of galaxies in the early universe through deep, wide-field surveys at wavelengths ranging from 2 to 200 microns. In the far-infrared wavelength band, ASTRO-F will conduct an all-sky survey like the IRAS survey with several tens of times higher sensitivity and several times better spatial resolution. In the near- and mid-infrared, wide area sky-surveys will be conducted over pre-selected portions of the sky in 13 bands ranging from 2-200microns. In addition to these photometric surveys, low-resolution spectroscopic capabilities are available for all wavelength bands. The ASTRO-F mission will produce a fundamental database for the next generation of advanced observatories, for example Herschel, and JWST, and will complement the SIRTF mission by virtue of its wide sky coverage.

scholarly journals Unveiling the nature of the unidentified gamma-ray sources: blazar counterparts at low radio frequencies

2013 ◽  
Vol 9 (S304) ◽  
pp. 95-95
Author(s):  
Francesco Massaro ◽  
R. D'Abrusco ◽  
M. Giroletti ◽  
A. Paggi ◽  
N. Masetti ◽  
...  
Keyword(s):  
Radio Emission ◽  
Gamma Ray ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Large Array ◽  
New Approach ◽  
Very Large Array ◽  
Very Low Frequency ◽  
Sky Survey ◽  
Order Of Magnitude

AbstractAbout one third of the gamma-ray sources detected by Fermi have still no firmly established counterpart at lower energies. Here we propose a new approach to find candidate counterparts for the unidentified gamma-ray sources (UGSs) based on the 325 MHz radio survey performed with Westerbork Synthesis Radio Telescope (WSRT) in the northern hemisphere. First we investigate the low-frequency radio properties of blazars, the largest known population of gamma-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO VLA Sky survey (NVSS). We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in literature to look for infrared and optical counterparts of the gamma-ray blazar candidates selected with the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research we identify 23 new gamma-ray blazar candidates out of 32 UGSs investigated. I will also present the first analysis of very low frequency radio emission of blazars based on the recent Very Large Array Low-Frequency Sky Survey (VLSS) at 74 MHz. I show that blazars present radio flat spectra when evaluated at 74 MHz, about an order of magnitude in frequency lower than previous analyses. The implications of these findings in the contest of the blazars – radio galaxies connection will be discussed.

scholarly journals Comparison of the Optical and Radio Reference Frames

1986 ◽  
Vol 7 ◽  
pp. 103-108 ◽  
Author(s):  
K. J. Johnston ◽  
Chr. de Vegt
Keyword(s):  
Radio Emission ◽  
Reference Frame ◽  
Radio Telescope ◽  
Reference Frames ◽  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Extragalactic Radio Sources ◽  
Optical Reference ◽  
Lack Of Knowledge

The Very Large Array (VLA) has made possible the measurement of the precise positions of the radio emission associated with stars. This allows the direct comparison of the optical reference frame (FK4) with the radio reference frame which is defined by the quasi-absolute positions of extragalactic radio sources. This comparison is limited by the small number of bright stars that display detectable radio emission and the lack of knowledge of the precise coincidence of the radio emission with the optical photocenter of the star. Since the VLA is the most sensitive astrometrically capable radio telescope, positions of the largest number of stars north of declination -20 degrees can be measured. The accuracy of the positions on the extragalactic reference frame should approach a milliarcsecond.

scholarly journals Fundamental differences in the radio properties of red and blue quasars: enhanced compact AGN emission in red quasars

2020 ◽  
Vol 494 (4) ◽  
pp. 4802-4818 ◽  
Author(s):  
V A Fawcett ◽  
D M Alexander ◽  
D J Rosario ◽  
L Klindt ◽  
S Fotopoulou ◽  
...  
Keyword(s):  
Star Formation ◽  
Radio Emission ◽  
Sloan Digital Sky Survey ◽  
Formation Processes ◽  
Very Large Array ◽  
Radio Detection ◽  
Extended Radio ◽  
Sky Survey ◽  
Tentative Evidence ◽  
Insight Into

ABSTRACT We have recently used the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey to show that red quasars have fundamentally different radio properties to typical blue quasars: a significant (factor ≈3) enhancement in the radio-detection fraction, which arises from systems around the radio-quiet threshold with compact (&lt;5 arcsec) radio morphologies. To gain greater insight into these physical differences, here we use the DR14 Sloan Digital Sky Survey (SDSS) and more sensitive, higher resolution radio data from the Very Large Array (VLA) Stripe 82 (S82) and VLA-COSMOS 3 GHz (C3GHz) surveys. With the S82 data, we perform morphological analyses at a resolution and depth three times that of the FIRST radio survey, and confirm an enhancement in radio-faint and compact red quasars over typical quasars; we now also find tentative evidence for an enhancement in red quasars with slightly extended radio structures (16–43 kpc at z = 1.5). These analyses are complemented by C3GHz, which is deep enough to detect radio emission from star-formation processes. From our data we find that the radio enhancement from red quasars is due to AGN activity on compact scales (≲43 kpc) for radio-intermediate–radio-quiet sources (−5 &lt; $\mathcal {R}$ &lt; −3.4, where $\mathcal {R}$ = $L_{\rm{1.4\,GHz}}/L_{6\mu\text{m}}$), which decreases at $\mathcal {R}$ &lt; −5 as the radio emission from star-formation starts to dilute the AGN component. Overall our results argue against a simple orientation scenario and are consistent with red quasars representing a younger, earlier phase in the overall evolution of quasars.

Infrared Wide-Field Surveys

1994 ◽  
Vol 161 ◽  
pp. 13-16
Author(s):  
N. Epchtein
Keyword(s):  
Near Infrared ◽  
Wide Field ◽  
Field Surveys ◽  
Sky Surveys ◽  
The Past ◽  
Infrared Spectral Range ◽  
Sky Survey ◽  
Array Technology ◽  
Infrared Spectral ◽  
Infrared Array

Optical wide-field sky surveys have long been basic tools of astronomical investigations. Their extension to the near infrared spectral range, unattainable with photographic techniques, is now possible thanks to the considerable improvements in infrared array technology that have been achieved in the past few years. The astronomical motivations for all-sky 2 μm surveys are summarized, and a brief technical description of the on-going projects, in particular DENIS (Deep Near Infrared Southern Sky Survey) that will be carried out at the European Southern Observatory in 1994–97, is presented.

scholarly journals Radio loudness along the quasar main sequence

2019 ◽  
Vol 630 ◽  
pp. A110 ◽  
Author(s):  
V. Ganci ◽  
P. Marziani ◽  
M. D’Onofrio ◽  
A. del Olmo ◽  
E. Bon ◽  
...  
Keyword(s):  
Black Hole ◽  
Radio Emission ◽  
Spectral Type ◽  
Main Sequence ◽  
Flux Ratio ◽  
Sloan Digital Sky Survey ◽  
Very Large Array ◽  
Black Hole Binaries ◽  
Line Region ◽  
Sky Survey

Context. When can an active galactic nucleus (AGN) be considered radio loud (RL)? Following the established view of the AGNs inner workings, an AGN is RL if associated with relativistic ejections emitting a radio synchrotron spectrum (i.e., it is a “jetted” AGN). In this paper we exploit the AGN main sequence that offers a powerful tool to contextualize radio properties. Aims. If large samples of optically-selected quasars are considered, AGNs are identified as RL if their Kellermann’s radio loudness ratio RK >  10. Our aims are to characterize the optical properties of different classes based on radio loudness within the main sequence and to test whether the condition RK >  10 is sufficient for the identification of RL AGNs, since the origin of relatively strong radio emission may not be necessarily due to relativistic ejection. Methods. A sample of 355 quasars was selected by cross-correlating the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters survey (FIRST) with the twelfth release of the Sloan Digital Sky Survey Quasar Catalog published in 2017. We classified the optical spectra according to their spectral types along the main sequence of quasars. For each spectral type, we distinguished compact and extended morphology (providing a FIRST-based atlas of radio maps in the latter case), and three classes of radio loudness: detected ( specific flux ratio in the g band and at 1.4 GHz, R′K < 10), intermediate (10 ≤ R′K < 70), and RL (R′K ≥ 70). Results. The analysis revealed systematic differences between radio-detected (i.e., radio-quiet), radio-intermediate, and RL classes in each spectral type along the main sequence. We show that spectral bins that contain the extreme Population A sources have radio power compatible with emission by mechanisms ultimately due to star formation processes. RL sources of Population B are characteristically jetted. Their broad Hβ profiles can be interpreted as due to a binary broad-line region. We suggest that RL Population B sources should be preferential targets for the search of black hole binaries, and present a sample of binary black hole AGN candidates. Conclusions. The validity of the Kellermann’s criterion may be dependent on the source location along the quasar main sequence. The consideration of the main sequence trends allowed us to distinguish between sources whose radio emission mechanisms is jetted from the ones where the mechanism is likely to be fundamentally different.

scholarly journals Luminous Late-time Radio Emission from Supernovae Detected by the Karl G. Jansky Very Large Array Sky Survey (VLASS)

2021 ◽  
Vol 923 (2) ◽  
pp. L24
Author(s):  
Michael C. Stroh ◽  
Giacomo Terreran ◽  
Deanne L. Coppejans ◽  
Joe S. Bright ◽  
Raffaella Margutti ◽  
...  
Keyword(s):  
Radio Emission ◽  
Gamma Ray ◽  
Mass Loss Rate ◽  
Core Collapse ◽  
Late Time ◽  
Shock Interaction ◽  
Large Array ◽  
Content Type ◽  
Very Large Array ◽  
Sky Survey

Abstract We present a population of 19 radio-luminous supernovae (SNe) with emission reaching L ν ∼ 1026–1029 erg s−1 Hz−1 in the first epoch of the Very Large Array Sky Survey (VLASS) at 2–4 GHz. Our sample includes one long gamma-ray burst, SN 2017iuk/GRB 171205A, and 18 core-collapse SNe detected at ≈1–60 yr after explosion. No thermonuclear explosion shows evidence for bright radio emission, and hydrogen-poor progenitors dominate the subsample of core-collapse events with spectroscopic classification at the time of explosion (79%). We interpret these findings in the context of the expected radio emission from the forward shock interaction with the circumstellar medium (CSM). We conclude that these observations require a departure from the single wind–like density profile (i.e., ρ CSM ∝ r −2) that is expected around massive stars and/or from a spherical Newtonian shock. Viable alternatives include the shock interaction with a detached, dense shell of CSM formed by a large effective progenitor mass-loss rate, M ̇ ∼ 10 − 4 – 10 − 1 M ⊙ yr−1 (for an assumed wind velocity of 1000 km s−1); emission from an off-axis relativistic jet entering our line of sight; or the emergence of emission from a newly born pulsar-wind nebula. The relativistic SN 2012ap that is detected 5.7 and 8.5 yr after explosion with L ν ∼ 1028 erg s−1 Hz−1 might constitute the first detections of an off-axis jet+cocoon system in a massive star. However, none of the VLASS SNe with archival data points are consistent with our model off-axis jet light curves. Future multiwavelength observations will distinguish among these scenarios. Our VLASS source catalogs, which were used to perform the VLASS cross-matching, are publicly available at https://doi.org/10.5281/zenodo.4895112.

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