- ID:
- ivo://CDS.VizieR/J/MNRAS/471/210
- Title:
- eMERGE Survey. I. VLA 5.5GHz sources
- Short Name:
- J/MNRAS/471/210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of the GOODS-N field obtained at 5.5GHz with the Karl G. Jansky Very Large Array. The central region of the field was imaged to a median rms of 3{mu}Jy/beam with a resolution of 0.5 arcsec. From a 14-arcmin diameter region, we extracted a sample of 94 radio sources with signal-to-noise ratio greater than 5. Near-IR identifications are available for about ~88 per cent of the radio sources. We used different multiband diagnostics to separate active galactic nuclei (AGNs), both radiatively efficient and inefficient, from star-forming galaxies. From our analysis, we find that about 80 per cent of our radio-selected sample is AGN dominated, with the fraction rising to 92 per cent when considering only the radio sources with redshift >1.5. This large fraction of AGN-dominated radio sources at very low flux densities (the median flux density at 5.5GHz is 42{mu}Jy), where star-forming galaxies are expected to dominate, is somewhat surprising and at odds with other results. Our interpretation is that both the frequency and angular resolution of our radio observations strongly select against radio sources whose brightness distribution is diffuse on a scale of several kpc. Indeed, we find that the median angular sizes of the AGN-dominated sources is around 0.2-0.3arcsec against 0.8 arcsec for star-forming galaxies. This highlights the key role that high frequency radio observations can play in pinpointing AGN-driven radio emission at {mu}Jy levels. This work is part of the eMERGE legacy project.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/865/56
- Title:
- Emission line & R-band continuum LCs of 17 QSOs
- Short Name:
- J/ApJ/865/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present reverberation mapping (RM) results for 17 high-redshift, high-luminosity quasars with good-quality R-band and emission-line light curves. We are able to measure statistically significant lags for Ly{alpha} (11 objects), Si IV (5 objects), C IV (11 objects), and C III] (2 objects). Using our results and previous lag determinations taken from the literature, we present an updated C IV radius-luminosity relation and provide for the first time radius-luminosity relations for Ly{alpha}, Si IV, and C III]. While in all cases the slopes of the correlations are statistically significant, the zero points are poorly constrained because of the lack of data at the low- luminosity end. We find that the emissivity-weighted distances from the central source of the Ly{alpha}, Si IV, and C III] line-emitting regions are all similar, which corresponds to about half that of the H{beta} region. We also find that 3/17 of our sources show an unexpected behavior in some emission lines, two in the Ly{alpha} light curve and one in the Si IV light curve, in that they do not seem to follow the variability of the UV continuum. Finally, we compute RM black hole (BH) masses for those quasars with highly significant lag measurements and compare them with C IV single-epoch (SE) mass determinations. We find that the RM-based BH mass determinations seem smaller than those found using SE calibrations.
- ID:
- ivo://CDS.VizieR/J/ApJ/880/127
- Title:
- EMPIRE: IRAM 30m dense gas survey
- Short Name:
- J/ApJ/880/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present EMPIRE, an IRAM 30m large program that mapped {lambda}=3-4mm dense gas tracers at ~1-2kpc resolution across the whole star-forming disk of nine nearby massive spiral galaxies. We describe the EMPIRE observing and reduction strategies and show new whole-galaxy maps of HCN(1-0), HCO^+^(1-0), HNC(1-0), and CO(1-0). We explore how the HCN-to-CO and IR-to-HCN ratios, observational proxies for the dense gas fraction and dense gas star formation efficiency, depend on host galaxy and local environment. We find that the fraction of dense gas correlates with stellar surface density, gas surface density, molecular-to-atomic gas ratio, and dynamical equilibrium pressure. In EMPIRE, the star formation rate per unit dense gas is anticorrelated with these same environmental parameters. Thus, although dense gas appears abundant in the central regions of many spiral galaxies, this gas appears relatively inefficient at forming stars. These results qualitatively agree with previous work on nearby galaxies and the Milky Way's Central Molecular Zone. To first order, EMPIRE demonstrates that the conditions in a galaxy disk set the gas density distribution and that the dense gas traced by HCN shows an environment-dependent relation to star formation. However, our results also show significant (+/-0.2dex) galaxy-to-galaxy variations. We suggest that gas structure below the scale of our observations and dynamical effects likely also play an important role.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/1057
- Title:
- EoR0 central field source catalog
- Short Name:
- J/MNRAS/458/1057
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Experiments that pursue detection of signals from the Epoch of Reionization (EoR) are relying on spectral smoothness of source spectra at low frequencies. This article empirically explores the effect of foreground spectra on EoR experiments by measuring high-resolution full-polarization spectra for the 586 brightest unresolved sources in one of the Murchison Widefield Array (MWA) EoR fields using 45h of observation. A novel peeling scheme is used to subtract 2500 sources from the visibilities with ionospheric and beam corrections, resulting in the deepest, confusion-limited MWA image so far. The resulting spectra are found to be affected by instrumental effects, which limit the constraints that can be set on source-intrinsic spectral structure. The sensitivity and power-spectrum of the spectra are analysed, and it is found that the spectra of residuals are dominated by point spread function sidelobes from nearby undeconvolved sources. We release a catalogue describing the spectral parameters for each measured source.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A93
- Title:
- EP Aqr ALMA and SPHERE observations
- Short Name:
- J/A+A/642/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cool evolved stars are known to be significant contributors to the enrichment of the interstellar medium through their dense and dusty stellar winds. High resolution observations of these outflows have shown them to possess high degrees of morphological complexity. We observed the asymptotic giant branch (AGB) star EP Aquarii with ALMA in band 6 and VLT/SPHERE/ZIMPOL in four filters the visible. Both instruments had an angular resolution of 0.025". These are follow-up observations to the lower-resolution 2016 ALMA analysis of EP Aquarii, which revealed that its wind possesses a nearly face-on, spiral-harbouring equatorial density enhancement, with a nearly pole-on bi-conical outflow. At the base of the spiral, the SiO emission revealed a distinct emission void approximately 0.4" to the west of the continuum brightness peak, which was proposed to be linked to the presence of a companion. The new ALMA data better resolve the inner wind and reveal that its morphology as observed in CO is consistent with hydrodynamical companion-induced perturbations. Assuming that photodissociation by the UV-field of the companion is responsible for the emission void in SiO, we deduced the spectral properties of the tentative companion from the size of the hole. We conclude that the most probable companion candidate is a white dwarf with a mass between 0.65 and 0.8M_{sun}_, though a solar-like companion could not be definitively excluded. The radial SiO emission shows periodic, low-amplitude perturbations. We tentatively propose that they could be the consequence of the interaction of the AGB wind with another much closer low-mass companion. The polarised SPHERE/ZIMPOL data show a circular signal surrounding the AGB star with a radius of ~0.1". Decreased signal along a PA of 138{deg} suggests that the dust is confined to an inclined ring-like structure, consistent with the previously determined wind morphology.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A54
- Title:
- ESO 435-02/ESO 435-016 ATCA HI images
- Short Name:
- J/A+A/605/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A fly-by interaction has been suggested to be one of the major explanations for enhanced star formation in blue compact dwarf (BCD) galaxies, yet no direct evidence for this scenario has been found to date. In the HI Parkes all-sky survey (HIPASS), ESO 435-IG 020 and ESO 435-G 016, a BCD pair were found in a common, extended gas envelope of atomic hydrogen, providing an ideal case to test the hypothesis that the starburst in BCDs can be indeed triggered by a fly-by interaction. Using high-resolution data from the Australia Telescope Compact Array (ATCA), we investigated HI properties and the spectral energy distribution (SED) of the BCD pair to study their interaction and star formation histories. The high-resolution HI data of both BCDs reveal a number of peculiarities, which are suggestive of tidal perturbation. Meanwhile, 40% of the HIPASS flux is not accounted for in the ATCA observations with no HI gas bridge found between the two BCDs. Intriguingly, in the residual of the HIPASS and the ATCA data, ~10% of the missing flux appears to be located between the two BCDs. While the SED-based age of the most dominant young stellar population is old enough to have originated from the interaction with any neighbors (including the other of the two BCDs), the most recent star formation activity traced by strong H{alpha} emission in ESO 435-IG 020 and the shear motion of gas in ESO 435-G 016, suggest a more recent or current tidal interaction. Based on these and the residual emission between the HIPASS and the ATCA data, we propose an interaction between the two BCDs as the origin of their recently enhanced star formation activity. The shear motion on the gas disk, potentially with re-accretion of the stripped gas, could be responsible for the active star formation in this BCD pair.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/74
- Title:
- Excited-state hydroxyl maser polarimetry
- Short Name:
- J/MNRAS/451/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present polarimetric maser observations with the Australia Telescope Compact Array of excited-state hydroxyl (OH) masers. We observed 30 fields of OH masers in full Stokes polarization with the Compact Array Broadband Backend at both the 6030 and 6035 MHz excited-state OH transitions, and the 6668 MHz methanol maser transition, detecting 70 sites of maser emission. Amongst the OH we found 112 Zeeman pairs, of which 18 exhibited candidate {pi} components. This is the largest single full polarimetric study of multiple sites of star formation for these frequencies, and the rate of 16 percent {pi} components clearly indicates that the {pi} component exists, and is comparable to the percentage recently found for ground-state transitions. This significant percentage of {pi} components, with consistent proportions at both ground- and excited-state transitions, argues against Faraday rotation suppressing the {pi} component emission. Our simultaneous observations of methanol found the expected low level of polarization, with no circular detected, and linear only found at the =<10 percent level for the brightest sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/612/511
- Title:
- Exoplanet radio emission
- Short Name:
- J/ApJ/612/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We predict the radio flux densities of the extrasolar planets in the current census, making use of an empirical relation - the radiometric Bode's law - determined from the five "magnetic" planets in the solar system (the Earth and the four gas giants). Radio emission from these planets results from solar wind-powered electron currents depositing energy in the magnetic polar regions. We find that most of the known extrasolar planets should emit in the frequency range 10-1000 MHz and, under favorable circumstances, have typical flux densities as large as 1mJy. We also describe an initial, systematic effort to search for radio emission in low radio frequency images acquired with the Very Large Array (VLA). The limits set by the VLA images (~300mJy) are consistent with, but do not provide strong constraints on, the predictions of the model.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A51
- Title:
- Extended CO structures in NGC6240
- Short Name:
- J/A+A/549/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep CO(1-0) observations of NGC6240 performed with the IRAM Plateau de Bure Interferometer (PdBI). NGC6240 is the prototypical example of a major galaxy merger in progress, caught at an early stage, with an extended, strongly-disturbed butterfly- like morphology and a heavily obscured active nucleus in the core of each progenitor galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/764
- Title:
- Extended radio emission in MOJAVE blazars
- Short Name:
- J/ApJ/710/764
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile "core-only" source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs.