- ID:
- ivo://CDS.VizieR/J/ApJ/704/548
- Title:
- Photometric properties of galaxies at z=4-6
- Short Name:
- J/ApJ/704/548
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new information on galaxies in the vicinity of luminous radio galaxies (RGs) and quasars at z~4, 5, and 6. These fields were previously found to contain overdensities of Lyman Break Galaxies (LBGs) or spectroscopic Ly{alpha} emitters (LAEs), which were interpreted as evidence for clusters-in-formation ("protoclusters"). We use Hubble Space Telescope and Spitzer data to infer stellar masses from stellar synthesis models calibrated against the Millennium Run simulations, and contrast our results with large samples of LBGs in more average environments as probed by the Great Observatories Origins Deep Survey (GOODS).
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- ID:
- ivo://CDS.VizieR/J/ApJ/723/492
- Title:
- Physical properties of GRS molecular clouds
- Short Name:
- J/ApJ/723/492
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the physical properties of 580 molecular clouds based on their ^12^CO and ^13^CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys (GRS). We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the interstellar medium is around 2.36. This relation, M=(228+/-18)R^2.36+/-0.04^, allows us to derive masses for an additional 170 Galactic Ring Survey (GRS) molecular clouds not covered by the UMSB survey. We derive the Galactic surface mass density of molecular gas and examine its spatial variations throughout the Galaxy. We find that the azimuthally averaged Galactic surface density of molecular gas peaks between Galactocentric radii of 4 and 5kpc. Although the Perseus arm is not detected in molecular gas, the Galactic surface density of molecular gas is enhanced along the positions of the Scutum-Crux and Sagittarius arms.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/1792
- Title:
- Pi Ghz Sky Survey (PiGSS). I.
- Short Name:
- J/ApJ/725/1792
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Pi GHz Sky Survey (PiGSS) is a key project of the Allen Telescope Array. PiGSS is a 3.1GHz survey of radio continuum emission in the extragalactic sky with an emphasis on synoptic observations that measure the static and time-variable properties of the sky. During the 2.5 year campaign, PiGSS will twice observe ~250000 radio sources in the 10000deg^2^ region of the sky with b>30{deg} to an rms sensitivity of ~1mJy. Additionally, sub-regions of the sky will be observed multiple times to characterize variability on timescales of days to years. We present here observations of a 10deg^2^ region in the Bootes constellation overlapping the NOAO Deep Wide Field Survey field. The PiGSS image was constructed from 75 daily observations distributed over a 4 month period and has an rms flux density between 200 and 250uJy. This represents a deeper image by a factor of 4-8 than we will achieve over the entire 10000deg^2^. We provide flux densities, source sizes, and spectral indices for the 425 sources detected in the image. We identify ~100 new flat-spectrum radio sources; we project that when completed PiGSS will identify 104 flat-spectrum sources. We identify one source that is a possible transient radio source. This survey provides new limits on faint radio transients and variables with characteristic durations of months.
- ID:
- ivo://CDS.VizieR/J/ApJ/739/76
- Title:
- Pi GHz Sky Survey (PiGSS). II.
- Short Name:
- J/ApJ/739/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from daily radio continuum observations of the Bootes field as part of the Pi GHz Sky Survey (PiGSS). These results are part of a systematic and unbiased campaign to characterize variable and transient sources in the radio sky. The observations include 78 individual epochs distributed over five months at a radio frequency of 3.1GHz with a median rms image noise in each epoch of 2.8mJy. We produce five monthly images with a median rms of 0.6mJy. No transient radio sources are detected in the daily or monthly images. At 15mJy, we set an upper limit (2{sigma}) to the surface density of one-day radio transients at 0.025deg^-2^. At 5mJy, we set an upper limit (2{sigma}) to the surface density of one-month radio transients at 0.18deg^-2^. We also produce light curves for 425 sources and explore the variability properties of these sources. Approximately 20% of the sources exhibit some variability on daily and monthly timescales. The maximum rms fractional modulations on the one-day and one-month timescales for sources brighter than 10mJy are 2 and 0.5, respectively. The probability of a daily fluctuation for all sources and all epochs by a factor of 10 is less than 10^-4^. We compare the radio to mid-infrared variability for sources in the field and find no correlation. Finally, we apply the statistics of transient and variable populations to constrain models for a variety of source classes.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A13
- Title:
- pi.01 Gru ALMA CO(3-2) data cube
- Short Name:
- J/A+A/633/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study follows up the previous analysis of lower-angular resolution data in which the kinematics and structure of the circumstellar envelope (CSE) around the S-type asymptotic giant branch (AGB) star pi^1^ Gruis were investigated. The AGB star has a known companion (at a separation of ~400AU) which cannot explain the strong deviations from spherical symmetry of the CSE. Recently, hydrodynamic simulations of mass transfer in closer binary systems have successfully reproduced the spiral-shaped CSEs found around a handful of sources. There is growing evidence for an even closer, undetected companion complicating the case of pi^1^ Gruis further. The improved spatial resolution allows for the investigation of the complex circumstellar morphology and the search for imprints on the CSE of the third component. We have observed the ^12^CO J=3-2 line emission from pi^1^ Gruis using both the compact and extended array of Atacama Large Millimeter/submillimeter Array (ALMA). The interferometric data has furthermore been combined with data from the ALMA total power (TP) array. The imaged brightness distribution has been used to constrain a non-local, non-LTE 3D radiative transfer model of the CSE. The high-angular resolution ALMA data have revealed the first example of a source on the AGB where both a faster bipolar outflow and a spiral pattern along the orbital plane can be seen in the gas envelope. The spiral can be traced in the low- to intermediate velocity (13-25km/s) equatorial torus. The largest spiral-arm separation is ~5.5" and consistent with a companion with an orbital period of ~330yrs and a separation of less than 70AU. The kinematics of the bipolar outflow is consistent with it being created during a mass-loss eruption where the mass-loss rate from the system increased by at least a factor of 5 during 10-15yrs. The spiral pattern is the result of an undetected companion. The bipolar outflow is the result of a rather recent mass-loss eruption event.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/93
- Title:
- PiGSS. III. ELAIS-N1, Coma & Lockman fields
- Short Name:
- J/ApJ/762/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a total of 459 repeated 3.1GHz radio continuum observations (of which 379 were used in a search for transient sources) of the ELAIS-N1, Coma, Lockman Hole, and NOAO Deep Wide Field Survey fields as part of the Pi GHz Sky Survey. The observations were taken approximately once per day between 2009 May and 2011 April. Each image covers 11.8 square degrees and has 100" FWHM resolution. Deep images for each of the four fields have rms noise between 180 and 310{mu}Jy, and the corresponding catalogs contain ~200 sources in each field. Typically 40-50 of these sources are detected in each single-epoch image. This represents one of the shortest cadence, largest area, multi-epoch surveys undertaken at these frequencies. We compare the catalogs generated from the combined images to those from individual epochs, and from monthly averages, as well as to legacy surveys. We undertake a search for transients, with particular emphasis on excluding false positive sources. We find no confirmed transients, defined here as sources that can be shown to have varied by at least a factor of 10. However, we find one source that brightened in a single-epoch image to at least six times the upper limit from the corresponding deep image. We also find a source associated with a z=0.6 quasar which appears to have brightened by a factor ~3 in one of our deep images, when compared to catalogs from legacy surveys. We place new upper limits on the number of transients brighter than 10mJy: fewer than 0.08 transients deg^-2^ with characteristic timescales of months to years; fewer than 0.02deg^-2^ with timescales of months; and fewer than 0.009deg^-2^ with timescales of days. We also plot upper limits as a function of flux density for transients on the same timescales.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A66
- Title:
- PKS 1549-79 ALMA data cubes & continuum images
- Short Name:
- J/A+A/632/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CO(1-0) and CO(3-2) Atacama Large Millimeter/submillimeter Array observations of the molecular gas in PKS 1549-79, as well as mm and very long baseline interferometry 2.3-GHz continuum observations of its radio jet. PKS 1549-79 is one of the closest young, radio-loud quasars caught in an on-going merger in which the active galactic nucleus (AGN) is in the first phases of its evolution. We detect three structures tracing the accretion and the outflow of molecular gas: kpc-scale tails of gas accreting onto PKS1549-79 from a merger, a circumnuclear disc in the inner few hundred parsec, and a very broad (>2300km/s) component detected in CO(1-0) at the position of the AGN. Thus, in PKS 1549-79 we see the co-existence of accretion and the ejection of gas. The line ratio CO(3-2)/CO(1-0) suggests that the gas in the circumnuclear-disc has both high densities and high kinetic temperatures. We estimate a mass outflow rate of at least 650M_{sun}_/yr. This massive outflow is confined to the inner region (r<120pc) of the galaxy, which suggests that the AGN drives the outflow. Considering the amount of molecular gas available in the central nuclear disc and the observed outflow rate, we estimate a time scale of 10^5^yr over which the AGN would be able to destroy the circumnuclear disc, although gas from the merger may come in from larger radii, rebuilding this disc at the same time. The AGN appears to self-regulate gas accretion to the centre and onto the super-massive black hole. Surprisingly, from a comparison with Hubble Space Telescope data, we find that the ionised gas outflow is more extended. Nevertheless, the warm outflow is about two orders of magnitude less massive than the molecular outflow. PKS 1549-79 does not seem to follow the scaling relation between bolometric luminosity and the relative importance of warm ionised and molecular outflows claimed to exist for other AGN. We argue that, although PKS 1549-79 hosts a powerful quasar nucleus and an ultra-fast outflow, the radio jet plays a significant role in producing the outflow, which creates a cocoon of disturbed gas that expands into the circumnuclear disc.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A9
- Title:
- PKS 1549-79 ALMA data cubes & continuum images
- Short Name:
- J/A+A/634/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of Fornax A taken at ~1GHz with the MeerKAT telescope and at ~6GHz with the Sardinia Radio Telescope (SRT). The sensitive (noise ~16uJy/beam), high-resolution (<10'') MeerKAT images show that the lobes of Fornax A have a double-shell morphology, where dense filaments are embedded in a diffuse and extended cocoon. We study the spectral properties of these components by combining the MeerKAT and SRT observations with archival data between 84MHz and 217GHz. For the first time, we show that multiple episodes of nuclear activity must have formed the extended radio lobes. The modelling of the radio spectrum suggests that the last episode of injection of relativistic particles into the lobes started ~24Myr ago and stopped 12Myr ago. More recently (~3Myr ago), a less powerful and short (<1Myr) phase of nuclear activity generated the central jets. Currently, the core may be in a new active phase. It appears that Fornax A is rapidly flickering. The dense environment around Fornax A has lead to a complex recent merger history for this galaxy, including mergers spanning a range of gas contents and mass ratios, as shown by the analysis of the galaxy's stellar- and cold-gas phases. This complex recent history may be the cause of the rapid, recurrent nuclear activity of Fornax A.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A42
- Title:
- PKS B1718-649 ALMA observations
- Short Name:
- J/A+A/614/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ALMA observations of the ^12^CO (2-1) line of the newly born (t_radio_~10^2^years) active galactic nucleus (AGN), PKS B1718-649. These observations reveal that the carbon monoxide in the innermost 15 kpc of the galaxy is distributed in a complex warped disk. In the outer parts of this disk, the CO gas follows the rotation of the dust lane and of the stellar body of the galaxy hosting the radio source. In the innermost kiloparsec, the gas abruptly changes orientation and forms a circumnuclear disk (r<~700pc) with its major axis perpendicular to that of the outer disk. Against the compact radio emission of PKS B1718-649 (r~2pc), we detect an absorption line at red-shifted velocities with respect to the systemic velocity ({Delta}v=+365+/-22km/s). This absorbing CO gas could trace molecular clouds falling onto the central super-massive black hole. A comparison with the near-infra red H_2_ 1-0 S(1) observations shows that the clouds must be close to the black hole (r<~75pc). The physical conditions of these clouds are different from the gas at larger radii, and are in good agreement with the predictions for the conditions of the gas when cold chaotic accretion triggers an active galactic nucleus. These observations on the centre of PKS B1718-649 provide one of the best indications that a population of cold clouds is falling towards a radio AGN, likely fuelling its activity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/369/449
- Title:
- PKS 0405-385 flux-density monitoring
- Short Name:
- J/MNRAS/369/449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The quasar PKS 0405-385 is one of three radio sources (the other two are PKS 1257-326 and J1819+385) which exhibit unusually strong and rapid interstellar scintillations at GHz frequencies. Such a behaviour suggests a nearby (<30pc away) scattering screen along the line of sight to these radio sources. While quasars PKS 1257-326 and J1819+385 scintillate continuously over several years of monitoring, PKS 0405-385 shows episodes of strong scintillations which last only a few months. Here, I present the results of flux-density monitoring of PKS 0405-385 over 6yr at four Stokes parameters and four frequencies. Two explanations of the episodic behaviour of interstellar scintillation in this source are discussed; morphological evolution of the source and changes in the properties of the interstellar medium along the line of sight.
