SUMSS: a wide-field radio imaging survey of the southern sky - II. The source catalogue

Hi absorption studies yield information on both AGN feeding and feedback processes. This AGN activity interacts with the neutral gas in compact radio sources, which are believed to represent the young or recently re-triggered AGN population. We present the results of a survey for Hi absorption in a sample of 66 compact radio sources at 0.040 < z < 0.096 with the Australia Telescope Compact Array. In total, we obtained seven detections, five of which are new, with a large range of peak optical depths (3% to 87%). Of the detections, 71% exhibit asymmetric, broad (∆v FWHM > 100 km s −1 ) features, indicative of disturbed gas kinematics. Such broad, shallow and offset features are also found within low-excitation radio galaxies which is attributed to disturbed circumnuclear gas, consistent with early-type galaxies typically devoid of a gas-rich disk. Comparing mid-infrared colours of our galaxies with Hi detections indicates that narrow and deep absorption features are preferentially found in late-type and high-excitation radio galaxies in our sample. These features are attributed to gas in galactic disks. By combining XMM-Newton archival data with 21-cm data, we find support that absorbed X-ray sources may be good tracers of HI content within the host galaxy. This sample extends previous Hi surveys in compact radio galaxies to lower radio luminosities and provides a basis for future work exploring the higher redshift universe.

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“…Column (5): S1.4 is the NVSS 1.4 GHz flux density (Condon et al 1998). Column (6): S0.843 is the SUMSS 843 MHz flux density (Mauch et al 2003).…”

Section: Columns (2) and (3)mentioning

confidence: 99%

Hi absorption in nearby compact radio galaxies

Glowacki

Allison

Sadler

et al. 2017

Mon. Not. R. Astron. Soc.

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“…Additionally, we can expect contributions to the 870 μm fluxes from radio continuum emission (synchrotron emission and/or bremsstrahlung). Three radio fluxes were estimated for Haro 11 with the NRAO VLA Sky Survey (8.46 and 1.4 GHz - Condon et al 1998) and the Sydney University Molonglo Sky Survey (843 MHz - Mauch et al 2003). We derive the 870 μm radio continuum contribution by extrapolation of the radio data tendancy (ν −1 ).…”

Section: Contamination Of the 870 μM Emission From Non-dust Originsmentioning

confidence: 99%

Probing the dust properties of galaxies up to submillimetre wavelengths

Galametz¹,

Madden²,

Galliano³

et al. 2009

A&A

200

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Aims. We study the dust properties of four low metallicity galaxies by modelling their spectral energy distributions. This modelling enables us to constrain the dust properties such as the mass, the temperature or the composition to characterise the global ISM properties in dwarf galaxies. Methods. We present 870 μm images of four low metallicity galaxies (NGC 1705, Haro 11, Mrk 1089 and UM 311) observed with the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope. We modeled their spectral energy distributions combining the submm observations of LABOCA, 2MASS, IRAS, Spitzer photometric data, and the IRS data for Haro 11. Results. We found that the PAH mass abundance is very low in these galaxies, 5 to 50 times lower than the PAH mass fraction of our Galaxy. We also found that a significant mass of dust is revealed when using submm constraints compared to that measured with only mid-IR to far-IR observations extending only to 160 μm. For NGC 1705 and Haro 11, an excess in submillimeter wavelengths was detected when we used our standard dust SED model. We rerun our SED procedure adding a cold dust component (10 K) to better describe the high 870 μm flux derived from LABOCA observations, which significantly improves the fit. We found that at least 70% of the dust mass of these two galaxies can reside in a cold dust component. We also showed that the subsequent dust-to-gas mass ratios, considering HI and CO observations, can be strikingly high for Haro 11 in comparison with what is usually expected for these low-metallicity environments. Furthermore, we derived the star formation rate of our galaxies and compared them to the Schmidt law. Haro 11 falls anomalously far from the Schmidt relation. These results may suggest that a reservoir of hidden gas could be present in molecular form not traced by the current CO observations. While there can be a significant cold dust mass found in Haro 11, the SED peaks at exceptionally short wavelengths (36 μm), also highlighting the importance of the much warmer dust component heated by the massive star clusters in Haro 11. We also derived the total IR luminosities derived from our models and compared them with relations that derive this luminosity from Spitzer bands. We found that the Draine & Li (2007) formula compares well to our direct IR determinations.

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“…We then cross-matched the remainder with either the NRAO VLA Sky Survey (NVSS) catalogue (Condon et al 1998) or the Sydney University Molonglo Sky Survey (SUMSS) catalogue (Mauch et al 2003), depending on the declination range of the dataset 4 . The cross-matching radius we used for most datasets was 1.2 arcmin.…”

Section: Source Extraction and Selectionmentioning

confidence: 99%

Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array

Loi

Murphy

Bell

et al. 2015

Mon. Not. R. Astron. Soc.

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Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 hours of data observed over 10 nights under quiet geomagnetic conditions (global storm index K p < 2), analysing the behaviour of short-timescale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10-20 arcsec) at 154 MHz are small enough that search radii of 1-2 arcmin should be sufficient for cross-matching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1-3% for the various nights. For sources fainter than ∼1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz.

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SUMSS: a wide-field radio imaging survey of the southern sky - II. The source catalogue

Cited by 805 publications

References 16 publications

Hi absorption in nearby compact radio galaxies

Hi absorption in nearby compact radio galaxies

Probing the dust properties of galaxies up to submillimetre wavelengths

Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array

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