The temperature of the WNM in the Milky Way

We report high spectral resolution Australia Telescope Compact Array HI 21 cm observations resulting in the detection of the warm neutral medium (WNM) of the Galaxy in absorption against two extragalactic radio sources, PKS 1814-637 and PKS 0407-658. The two lines of sight were selected on the basis of the simplicity of their absorption profiles and the strength of the background sources; the high velocity resolution of the spectra then enabled us to estimate the kinetic temperatures of the absorbing gas by fitting multiple Gaussians to the absorption profiles. Four separate WNM components were detected toward the two sources, with peak optical depths $\tau_{max} = (1.0 \pm 0.08) \times 10^{-2}$, $(1.4 \pm 0.2) \times 10^{-3}$, $(2.2 \pm 0.5) \times 10^{-3}$ and $(3.4 \pm 0.5) \times 10^{-3}$ and kinetic temperatures $T_{k} = 3127 \pm 300$ K, $3694 \pm 1595$ K, $3500 \pm 1354$ K and $2165 \pm 608$ K respectively. All four components were thus found to have temperatures in the thermally unstable range $500 < T_{k} < 5000$ K; this suggests that thermal equilibrium has not been reached throughout the WNM.Comment: 5 pages, 6 figures. Accepted for publication in MNRAS (Letters). Minor typos removed to match version in pres

On the relationship between a giant radio galaxy MSH 05-22 and the ambient large-scale galaxy structure

We present a comparison of the properties of a giant radio galaxy and the ambient intergalactic medium, whose properties are inferred from the large-scale distribution in galaxies. The double lobes of the radio galaxy MSH 05-22 are giant--1.8 Mpc projected linear size--and interacting with the environment outside the interstellar medium and coronal halo associated with the host galaxy. The radio lobes appear to be relicts and the double structure is asymmetric. We have examined the large-scale structure in the galaxy distribution surrounding the radio source. The host galaxy of MSH 05-22 is associated with a small group that lies close to the boundary of sheet-like and filamentary density enhancements, and adjacent to a void. Assuming that the galaxies trace gas, the asymmetries in the radio morphology in this case study appear related to the anisotropy in the medium. However, the observed overdensities and structure formation models for the heating of the intergalactic medium (IGM) suggest a density-temperature product for the IGM environment that is an order of magnitude below that expected from the properties of the radio source. The discordance suggests that even sources like MSH 05-22, which are observed in the relatively low-density IGM environment associated with the filamentary large-scale structure and have multiple signatures of being relicts, may be overpressured and evolving towards an equilibrium relaxed state with the ambient IGM. Alternately, it is speculated that astrophysical feedback originating in galaxy overdensities observed 1-2 Mpc to the N and NE of MSH 05-22 might be the mechanism for the heating of the ambient IGM gas.Comment: 27 pages including 1 table and 13 figures. To appear in Ap

On the Relationship between a Giant Radio Galaxy MSH 05-22 and the Ambient Large-Scale Galaxy Structure

We present a comparison of the properties of a giant radio galaxy and the ambient intergalactic medium, whose properties are inferred from the large-scale distribution in galaxies. The double lobes of the radio galaxy MSH 05-22 are giant - 1.8 Mpc projected linear size - and interact with the environment outside the interstellar medium and coronal halo associated with the host galaxy. The radio lobes appear to be relicts, and the double structure is asymmetric. We have examined the large-scale structure in the galaxy distribution surrounding the radio source. The host galaxy of MSH 05-22 is associated with a small group that lies close to the boundary of sheetlike and filamentary density enhancements, and adjacent to a void. Assuming that the galaxies trace gas, the asymmetries in the radio morphology in this case study appear related to the anisotropy in the medium. However, the observed overdensities and structure formation models for the heating of the intergalactic medium (IGM) suggest a density-temperature product for the IGM environment that is an order of magnitude below that expected from the properties of the radio source. The discordance suggests that even sources like MSH 05-22, which are observed in the relatively low-density IGM environment associated with the filamentary large-scale structure and have multiple signatures of being relicts, may be overpressured and evolving toward an equilibrium relaxed state with the ambient IGM. Alternately, it is speculated that astrophysical feedback originating in galaxy overdensities observed 1-2 Mpc to the north and northeast of MSH 05-22 might be the mechanism for the heating of the ambient IGM gas

The temperature of the warm neutral medium in the milky way

We report high-spectral-resolution Australia Telescope Compact Array (ATCA) H I 21-cm observations resulting in the detection of the warm neutral medium (WNM) of the Galaxy in absorption against two extragalactic radio sources, PKS 1814-637 and PKS 0407-658. The two lines of sight were selected on the basis of the simplicity of their absorption profiles and the strength of the background sources; the high velocity resolution of the spectra then enabled us to estimate the kinetic temperatures of the absorbing gas by fitting multiple Gaussians to the absorption profiles. Four separate WNM components were detected towards the two sources, with peak optical depths tmax= (1.0 ± 0.08) × 10<SUP>−2</SUP>, (1.4 ± 0.2) × 10<SUP>−3</SUP>, (2.2 ± 0.5) × 10<SUP>−3</SUP> and (3.4 ± 0.5) × 10<SUP>−3</SUP> and kinetic temperatures T<SUB>k</SUB>= 3127 ± 300, 3694 ± 1595, 3500 ± 1354 and 2165 ± 608 K, respectively. All four components were thus found to have temperatures in the thermally unstable range 500 &lt; T<SUB>k</SUB> &lt; 5000 K; this suggests that thermal equilibrium has not been reached throughout the WNM

What Gamma-rays tell us about jets

The combined synchrotron and inverse Compton emission from jets provide us with essential information on the properties of jets within 100-1000 gravitational radii from the black hole. In some jets the inferred magnetic field is below equipartition and in MKN 501 and MKN 421, recent models imply Doppler factors of approximately 50. Both of these features confront jet-launching models with substantial challenges. In MKN 421 and MKN 501 the jets must decelerate before they reach the parsec scale and this is in fact physically consistent with conservation of energy and momentum in this region. The correlation between the peak Lorentz factor and the inverse of the magnetic plus photon energy density is most directly explained if the shocks in blazar jets are produced by intrinsic jet instabilities rather than variations in the output of the black hole. Recent analysis of a restarting radio jet galaxy provide additional evidence for hyper-relativistic jets

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures

We report the final redshift release of the 6dF Galaxy Survey, a combined redshift and peculiar velocity survey over the southern sky (|b|>10 deg). Its 136,304 spectra have yielded 110,256 new extragalactic redshifts and a new catalogue of 125,071 galaxies making near-complete samples with (K, H, J, r_F, b_J) <= (12.65, 12.95, 13.75, 15.60, 16.75). The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online database. We describe changes to the information in the database since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10% of the sample. Here we provide redshift maps of the southern local universe with z<=0.1, showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS database is http://www-wfau.roe.ac.uk/6dFGSComment: 18 pages, 9 figures, submitted to MNRAS. Higher resolution version available from http://www.aao.gov.au/6dFGS/Publication