- 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.
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Search Results
- 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/MNRAS/437/1828
- Title:
- ExoMol line list for HCN and HNC
- Short Name:
- J/MNRAS/437/1828
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A revised rotation-vibration line list for the combined hydrogen cynanide (HCN)/hydrogen isocyanide (HNC) system is presented. The line list uses ab initio transition intensities calculated previously (Harris et al., 2002ApJ...578..657H) and extensive datasets of recently measured experimental energy levels. The resulting line list has significantly more accurate wavelengths than previous ones for these systems. An improved value for the separation between HCN and HNC is adopted leading to an approximately 25% lower predicted thermal population of HNC as a function of temperature in the key 2000 to 3000K region. Temperature-dependent partition functions and equilibrium constant are presented. The line lists are validated by comparison with laboratory spectra and are presented in full as supplementary data to the article and at www.exomol.com.
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/2877
- Title:
- Extended radio sources in ATLBS
- Short Name:
- J/MNRAS/434/2877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the environments of extended radio sources in the Australia Telescope Low-Brightness Survey (ATLBS). The radio sources were selected from the ATLBS Extended Source Sample, which is a well defined sample containing the most extended of radio sources in the ATLBS sky survey regions. The environments were analysed using 4-m Cerro-Tololo Inter-American Observatory Blanco telescope observations carried out for ATLBS fields in the Sloan Digital Sky Survey r' band. We have estimated the properties of the environments using smoothed density maps derived from galaxy catalogues constructed using these optical imaging data. The angular distribution of galaxy density relative to the axes of the radio sources has been quantified by defining anisotropy parameters that are estimated using a new method presented here. Examining the anisotropy parameters for a subsample of extended double radio sources that includes all sources with pronounced asymmetry in lobe extents, we find good evidence for environmental anisotropy being the dominant cause for lobe asymmetry in that higher galaxy density occurs almost always on the side of the shorter lobe, and this validates the usefulness of the method proposed and adopted here. The environmental anisotropy parameters have been used to examine and compare the environments of Fanaroff-Riley Class I (FRI) and Fanaroff-Riley Class II (FRII) radio sources in two redshift regimes (z<0.5 and z>0.5). Wide-angle tail sources and head-tail sources lie in the most overdense environments. The head-tail source environments (for the HT sources in our sample) display dipolar anisotropy in that higher galaxy density appears to lie in the direction of the tails. Excluding the head-tail and wide-angle tail sources, subsamples of FRI and FRII sources from the ATLBS appear to lie in similar moderately overdense environments, with no evidence for redshift evolution in the regimes studied herein.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/5063
- Title:
- Extended sources in SCORPIO at 2.1GHz
- Short Name:
- J/MNRAS/490/5063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of a large sample of extended radio sources in the Stellar Continuum Originating from Radio Physics In Ourgalaxy (SCORPIO) field, observed and resolved by the Australia Telescope Compact Array. SCORPIO, a pathfinder project for addressing the early operations of the Australia SKA Pathfinder, is a survey of ~5 square degrees between 1.4 and 3.1GHz, centred at l=343.5{deg}, b=0.75{deg}, and with an angular resolution of about 10 arcsec. It is aimed at understanding the scientific and technical challenges to be faced by future Galactic surveys. With a mean sensitivity around 100uJy/beam and the possibility to recover angular scales at least up to 4 arcmin, we extracted 99 extended sources, 35 of them detected for the first time. Among the 64 known sources 55 had at least a tentative classification in literature. Studying the radio morphology and comparing the radio emission with infrared we propose as candidates six new HII regions, two new planetary nebulae, two new luminous blue variable or Wolf-Rayet stars, and three new supernova remnants. This study provides an overview of the potentiality of future radio surveys in terms of Galactic source extraction and characterization and a discussion on the difficulty to reduce and analyse interferometric data on the Galactic plane.
- ID:
- ivo://CDS.VizieR/J/ApJ/678/96
- Title:
- Extragalactic H2O masers
- Short Name:
- J/ApJ/678/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Green Bank Telescope, we conducted a "snapshot" survey for water maser emission toward the nuclei of 611 galaxies and detected eight new sources. The sample consisted of nearby (v<5000km/s) and luminous (M_B_<-19.5) galaxies, some with known nuclear activity but most not previously known to host AGNs. Our detections include both megamasers associated with AGNs and relatively low luminosity masers probably associated with star formation. The detection in UGC 3789 is particularly intriguing because the spectrum shows both systemic and high-velocity lines indicative of emission from an AGN accretion disk seen edge-on. Based on 6 months of monitoring, we detected accelerations among the systemic features ranging from 2 to 8km/s/yr, the larger values belonging to the most redshifted systemic components. High-velocity maser lines in UGC 3789 show no detectable drift over the same period. Although UGC 3789 was not known to be an AGN prior to this survey, the presence of a disk maser is strong evidence for nuclear activity, and an optical spectrum obtained later has confirmed it. With follow-up observations, it may be possible to measure a geometric distance to UGC 3789.
- ID:
- ivo://CDS.VizieR/J/AJ/109/2318
- Title:
- Extragalactic IRAS sources
- Short Name:
- J/AJ/109/2318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extragalactic sources detected at lambda=60um were selected from the IRAS Faint Source Catalog, Version 2 (Cat. II/156) by the criterion S(60um)>=S(12um). They were identified by position coincidence with radio sources stronger than 25mJy at 4.85GHz in the 6.0sr declination band 0deg<Dec.<+75deg (excluding the 0.05sr region 12h40m<R.A.<14h40m, 0deg<Dec.<+5deg) and with radio sources stronger than 80mJy in the 3.4sr area 0h<R.A.<20h, -40deg<Dec.<0deg (plus the region 12h40m<R.A.<14h40m, 0deg<Dec.<+5deg). Fields containing new candidate identifications were mapped by the VLA at 4.86GHz with about 15" FWHM resolution. Difficult cases were confirmed or rejected with the aid of accurate (sigma~1") radio and optical positions. The final sample of 354 identifications in Omega=9.4sr is reliable and large enough to contain statistically useful numbers of radio-loud FIR galaxies and quasars. The logarithmic FIR/radio flux ratio parameter q can be used to distinguish radio sources powered by "starbursts" from those powered by "monsters." Starbursts and normal spiral galaxies in a lambda=60um flux-limited sample have a narrow (sigma_q=0.14+/-0.01) q distribution with mean <q>=2.74+/-0.01, and none have "warm" FIR spectra [{alpha}(25um, 60um)<1.5]. The absence of radio-quiet (but not completely silent) blazars indicates that nearly all blazars become optically thin at frequencies {nu}<~100GHz. Nonthermal sources with steep FIR/optical spectra and dust-embedded sources visible only at FIR and radio wavelengths must be very rare.
