arXiv subjects

R. Kothes

Publications and source records attributed to R. Kothes.

At least 55 records · Page 3Linked to original sources

arXiv2014

The Emission Nebula Sh 2-174: A Radio Investigation of the Surrounding Region

Sh 2-174 is believed to be either a planetary nebula (PN) or ionized, ambient interstellar medium (ISM). We present in this paper 1420 MHz polarization, 1420 MHz total intensity (Stokes-I), and neutral hydrogen (HI) images of the region around Sh 2-174. The radio images address not only the nature of the object, but also the history of the relationship between Sh 2-174 and its surrounding environment. The HI images show that Sh 2-174 sits presently at the center of a 1.2 deg x 0.4 deg cloud. The Stokes-I image shows thermal emission peaks coincident with the R-band optical nebula, as well as low-surface-brightness emission from an ionized "halo" around Sh 2-174 and from an ionized "plateau" extending southeast from the cloud. The polarization images reveal Faraday-rotation structures along the projected trajectory of Sh 2-174, including a high-contrast structure with "arms" that run precisely along the eastern edge of the HI cloud and a wide central region which merges with the downstream edge of Sh 2-174. The high-contrast structure is consistent with an ionized tail which has both early-epoch (before Sh 2-174 entered the cloud) and present-epoch (after Sh 2-174 entered the cloud) components. Furthermore, our rotation-measure analysis indicates that the ISM magnetic field is deflected at the leading edge of Sh 2-174. The downstream tail and upstream field deflection point to a PN-ISM interaction. Our estimated space velocity for the host white dwarf (GD~561) demonstrates that Sh 2-174 entered the cloud approximately 27,000 yr ago, and gives a PN-ISM interaction timescale less than approximately 200,000 yr. We estimate an ambient magnetic field in the cloud of 11 +/- 3 microGauss.

astro-ph.GA↗

arXiv2014

XMM-Newton and Canadian Galactic Plane Survey Observations of the Supernova Remnant G107.5-1.5

We present an XMM-Newton observation of the highly polarized low-surface brightness supernova remnant G107.5-1.5, discovered with the Canadian Galactic Plane Survey (CGPS). We do not detect diffuse X-ray emission from the SNR and set an upper limit on the surface brightness of ~2 x 10^30 erg arcmin^-2 s^-1, at an assumed distance of 1.1 kpc. We found eight bright point sources in the field, including the ROSAT source 1RXS J225203.8+574249 near the centre of the radio shell. Spectroscopic analysis of some of the embedded point sources, including the ROSAT source, has been performed, and all eight sources are most likely ruled out as the associated neutron star, primarily due to counterpart bright stars in optical and infrared bands. Timing analysis of the bright point sources yielded no significant evidence for pulsations, but, due to the timing resolution, only a small part of the frequency space could be searched. An additional ten fainter point sources were identified in the vicinity of the SNR. Further X-ray observation of these and the region in the vicinity of the radio shell may be warranted.

astro-ph.HE↗

arXiv2014

The Deep Full-Stokes Radio Sky

The new broad-band capabilities of large radio interferometers such as the GMRT and JVLA allow for long-integration mosaic imaging observations to create ultra-deep full-polarization images of the sky over wide frequency ranges. Achieving rms sensitivities of order 1 $μ$Jy, these observations explore the radio source population at flux densities well below the regime dominated by classical radio galaxies and Active Galactic Nuclei. We present initial results from radio sources revealed with deep mosaicking observations with the GMRT and JVLA at respectively 0.6 and 5 GHz, and evidence that the $μ$Jy sensitivity level marks the transition to detection of polarized emission from a population of sources dominated by emission from magnetic fields in the disks of starburst and normal galaxies.

astro-ph.GA↗

arXiv2014

Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey

Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization dataset at 1.4 GHz covering an area of 1060 deg$^2$. The data analyzed are a combination of data from the 100-m Effelsberg Telescope, the 26-m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from $\ell \approx 60$ to $\ell \approx 10^4$ and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at $b= 9^{\circ}$, associated with the disk-halo transition in a 15$^{\circ}$ region around $l=108^{\circ}$. Localized variations in the index are found toward HII regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by H$α$ emission) indicating that the thermal emission depolarizes background synchrotron emission.

astro-ph.GA↗

arXiv2014

Radio-continuum study of Large Magellanic Cloud Supernova Remnant J0509-6731

We present a detailed study of Australia Telescope Compact Array (ATCA) observations ($λ$ = 20, 13, 6 & 3~cm) of supernova remnant (SNR) J0509--6731 in the Large Magellanic Cloud (LMC). The remnant has a ring morphology with brightened regions towards the south-western limb. We also find a second brightened inner ring which is only seen in the radio-continuum. The SNR is almost circular, with a diameter ranging from 7 to 8~pc, and a steep radio spectral index between 36 and 3~cm of $α=-0.73\pm0.02$, which is characteristic of younger SNRs. We also report detection of radially orientated polarisation across the remnant at 6~cm, with a mean fractional polarisation level of $P\cong$~(26~$\pm$~13)%. We find the magnetic field ($\sim$168~$μ$G) and $Σ- D$ ($Σ= $ $1.1\times 10^{-19}$~W m$^{-2}$~Hz$^{-1}$~sr$^{-1}$ , $D=$ 7.35~pc) to be consistent with other young remnants.

astro-ph.GA↗

arXiv2013

The Science Cases for Building a Band 1 Receiver Suite for ALMA

We present the various science cases for building Band 1 receivers as part of ALMA's ongoing Development Program. We describe the new frequency range for Band 1 of 35-52 GHz, a range chosen to maximize the receiver suite's scientific impact. We first describe two key science drivers: 1) the evolution of grains in protoplanetary disks and debris disks, and 2) molecular gas in galaxies during the era of re-ionization. Studies of these topics with Band 1 receivers will significantly expand ALMA's Level 1 Science Goals. In addition, we describe a host of other exciting continuum and line science cases that require ALMA's high sensitivity and angular resolution. For example, ALMA Band 1 continuum data will probe the Sunyaev-Zel'dovich Effect in galaxy clusters, Very Small Grains and spinning dust, ionized jets from young stars, spatial and flaring studies of Sgr A*, the acceleration sites of solar flares, pulsar wind nebulae, radio supernovae, and X-ray binaries. Furthermore, ALMA Band 1 line data will probe chemical differentiation in cloud cores, complex carbon chain molecules, extragalactic radio recombination lines, masers, magnetic fields through Zeeman effect measurements, molecular outflows from young stars, the co-evolution of star formation and active galactic nuclei, and the molecular content of galaxies at z ~ 3. ALMA provides similar to better sensitivities than the JVLA over 35-50 GHz, with differences increasing with frequency. ALMA's smaller antennas and shorter baselines, greater number of baselines, and single-dish capabilities, however, give it a significant edge for observing extended emission, making wide-field maps (mosaics), or attaining high image fidelity, as required by the described science cases.

astro-ph.IM↗

arXiv2013

X-ray Observations of the Supernova Remnant CTB 87 (G74.9+1.2): An Evolved Pulsar Wind Nebula

Pulsar wind nebulae (PWNe) studies with the Chandra X-ray Observatory have opened a new window to address the physics of pulsar winds, zoom on their interaction with their hosting supernova remnant (SNR) and interstellar medium, and identify their powering engines. We here present a new 70 ks, plus an archived 18 ks, Chandra ACIS observation of the SNR CTB 87 (G74.9+1.2), classified as a PWN with unusual radio properties and poorly studied in X-rays. We find that the peak of the X-ray emission is clearly offset from the peak of the radio emission by ~100" and located at the southeastern edge of the radio nebula. We detect a point source - the putative pulsar - at the peak of the X-ray emission and study its spectrum separately from the PWN. This new point source, CXOU J201609.2+371110, is surrounded by a compact nebula displaying a torus-like structure and possibly a jet. A more extended diffuse nebula is offset from the radio nebula, extending from the point source to the northwest for ~250" The spectra of the point source, compact nebula and extended diffuse nebula are all well described by a power law model with a photon index of 1.1 (0.7-1.6), 1.2 (0.9-1.4) and 1.7 (1.5-1.8), respectively, for a column density N_H = 1.38 (1.21-1.57) x 10^22 cm^-2 (90% confidence). The total X-ray luminosity of the source is ~1.6 x 10^34 erg s^-1 at an assumed distance of 6.1 kpc, with ~2% and 6% contribution from the point source and compact nebula, respectively. The observed properties suggest that CTB 87 is an evolved (~5-28 kyr) PWN, with the extended radio emission likely a `relic' PWN, as in Vela-X and G327.1-1.1. To date, however, there is no evidence for thermal X-ray emission from this SNR, and the SNR shell is still missing, suggesting expansion into a low-density medium (n_0 < 0.2 cm^-3, assuming D = 6.1 kpc), likely caused by a stellar wind bubble blown by the progenitor star.

astro-ph.HE↗

arXiv2012

The Science Case for Building a Band 1 Receiver Suite for ALMA

We present a set of compelling science cases for the ALMA Band 1 receiver suite. For these cases, we assume in tandem the updated nominal Band 1 frequency range of 35-50 GHz with a likely extension up to 52 GHz; together these frequencies optimize the Band 1 science return. The scope of the science cases ranges from nearby stars to the re-ionization edge of the Universe. Two cases provide additional leverage on the present ALMA Level One Science Goals and are seen as particularly powerful motivations for building the Band 1 Receiver suite: (1) detailing the evolution of grains in protoplanetary disks, as a complement to the gas kinematics, requires continuum observations out to ~35 GHz (~9mm); and (2) detecting CO 3-2 line emission from galaxies like the Milky Way during the epoch of re-ionization, i.e., 6 < z < 10, also requires Band 1 receiver coverage. The range of Band 1 science is wide, however, and includes studies of very small dust grains in the ISM, pulsar wind nebulae, radio supernovae, X-ray binaries, the Galactic Center (i.e., Sgr A*), dense cloud cores, complex carbon-chain molecules, masers, magnetic fields in the dense ISM, jets and outflows from young stars, distant galaxies, and galaxy clusters (i.e., the Sunyaev-Zel'dovich Effect). A comparison of ALMA and the Jansky VLA (JVLA) at the same frequencies of Band 1 finds similar sensitivity performance at 40-50 GHz, with a slight edge for ALMA at higher frequencies (e.g., within a factor of 2 for continuum observations). With its larger number of instantaneous baselines, however, ALMA Band 1data will have greater fidelity than those from the JVLA at similar frequencies.

astro-ph.IM↗

arXiv2012

The JCMT 12CO(3-2) Survey of the Cygnus X Region: I. A Pathfinder

Cygnus X is one of the most complex areas in the sky. This complicates interpretation, but also creates the opportunity to investigate accretion into molecular clouds and many subsequent stages of star formation, all within one small field of view. Understanding large complexes like Cygnus X is the key to understanding the dominant role that massive star complexes play in galaxies across the Universe. The main goal of this study is to establish feasibility of a high-resolution CO survey of the entire Cygnus X region by observing part of it as a Pathfinder, and to evaluate the survey as a tool for investigating the star-formation process. A 2x4 degree area of the Cygnus X region has been mapped in the 12CO(3-2) line at an angular resolution of 15" and a velocity resolution of ~0.4km/s using HARP-B and ACSIS on the James Clerk Maxwell Telescope. The star formation process is heavily connected to the life-cycle of the molecular material in the interstellar medium. The high critical density of the 12CO(3-2) transition reveals clouds in key stages of molecule formation, and shows processes that turn a molecular cloud into a star. We observed ~15% of Cygnus X, and demonstrated that a full survey would be feasible and rewarding. We detected three distinct layers of 12CO(3-2) emission, related to the Cygnus Rift (500-800 pc), to W75N (1-1.8 kpc), and to DR21 (1.5-2.5 kpc). Within the Cygnus Rift, HI self-absorption features are tightly correlated with faint diffuse CO emission, while HISA features in the DR21 layer are mostly unrelated to any CO emission. 47 molecular outflows were detected in the Pathfinder, 27 of them previously unknown. Sequentially triggered star formation is a widespread phenomenon.

astro-ph.GA↗

arXiv2011

Discovery of an Energetic Pulsar Associated with SNR G76.9+1.0

We report the discovery of PSR J2022+3842, a 24 ms radio and X-ray pulsar in the supernova remnant G76.9+1.0, in observations with the Chandra X-ray telescope, the Robert C. Byrd Green Bank Radio Telescope, and the Rossi X-ray Timing Explorer (RXTE). The pulsar's spin-down rate implies a rotation-powered luminosity Edot = 1.2 x 10^{38} erg/s, a surface dipole magnetic field strength B_s = 1.0 x 10^{12} G, and a characteristic age of 8.9 kyr. PSR J2022+3842 is thus the second-most energetic Galactic pulsar known, after the Crab, as well as the most rapidly-rotating young, radio-bright pulsar known. The radio pulsations are highly dispersed and broadened by interstellar scattering, and we find that a large (delta-f / f ~= 1.9 x 10^{-6}) spin glitch must have occurred between our discovery and confirmation observations. The X-ray pulses are narrow (0.06 cycles FWHM) and visible up to 20 keV, consistent with magnetospheric emission from a rotation-powered pulsar. The Chandra X-ray image identifies the pulsar with a hard, unresolved source at the midpoint of the double-lobed radio morphology of SNR G76.9+1.0 and embedded within faint, compact X-ray nebulosity. The spatial relationship of the X-ray and radio emissions is remarkably similar to extended structure seen around the Vela pulsar. The combined Chandra and RXTE pulsar spectrum is well-fitted by an absorbed power-law model with column density N_H = (1.7\pm0.3) x 10^{22} cm^{-2} and photon index Gamma = 1.0\pm0.2; it implies that the Chandra point-source flux is virtually 100% pulsed. For a distance of 10 kpc, the X-ray luminosity of PSR J2022+3842 is L_X(2-10 keV) = 7.0 x 10^{33} erg s^{-1}. Despite being extraordinarily energetic, PSR J2022+3842 lacks a bright X-ray wind nebula and has an unusually low conversion efficiency of spin-down power to X-ray luminosity, L_X/Edot = 5.9 x 10^{-5}.

astro-ph.HE↗

arXiv2010

Faraday Rotation in the Tail of the Planetary Nebula DeHt 5

We present 1420 MHz polarization images of a 5x5 degree region around the planetary nebula (PN) DeHt 5. The images reveal narrow Faraday-rotation structures on the visible disk of DeHt 5, as well as two wider, tail-like, structures "behind" DeHt 5. Though DeHt 5 is an old PN known to be interacting with the interstellar medium (ISM), a tail has not previously been identified for this object. The innermost tail is approximately 3 pc long and runs away from the north-east edge of DeHt 5 in a direction roughly opposite that of the sky-projected space velocity of the white dwarf central star, WD 2218+706. We believe this tail to be the signature of ionized material ram-pressure stripped and deposited downstream during a >74,000 yr interaction between DeHt 5 and the ISM. We estimate the rotation measure (RM) through the inner tail to be -15 +/- 5 rad/m^2, and, using a realistic estimate for the line-of-sight component of the ISM magnetic field around DeHt 5, derive an electron density in the inner tail of n_e = 3.6 +/- 1.8 cm^-3. Assuming the material is fully ionized, we estimate a total mass in the inner tail of 0.68 +/- 0.33 solar masses, and predict that 0.49 +/- 0.33 solar masses was added during the PN-ISM interaction. The outermost tail consists of a series of three roughly circular components, which have a collective length of approximately 11.0 pc. This tail is less conspicuous than the inner tail, and may be the signature of the earlier interaction between the WD 2218+706 asymptotic giant branch (AGB) progenitor and the ISM. The results for the inner and outer tails are consistent with hydrodynamic simulations, and may have implications for the PN missing-mass problem as well as for models which describe the impact of the deaths of intermediate-mass stars on the ISM.

astro-ph.GA↗

arXiv2010

A Survey of the Polarized Emission from the Galactic Plane at 1420 MHz with Arcminute Angular Resolution

Context: Observations of polarized emission are a significant source of information on the magnetic field that pervades the Interstellar Medium of the Galaxy. Despite the acknowledged importance of the magnetic field in interstellar processes, our knowledge of field configurations on all scales is seriously limited. Aims: This paper describes an extensive survey of polarized Galactic emission at 1.4 GHz that provides data with arcminute resolution and complete coverage of all structures from the broadest angular scales to the resolution limit, giving information on the magneto-ionic medium over a wide range of interstellar environments. Methods: Data from the DRAO Synthesis Telescope, the Effelsberg 100-m Telescope, and the DRAO 26-m Telescope have been combined. Angular resolution is ~1' and the survey extends from l = 66 deg to l = 175 deg over a range -3 deg < b < 5 deg along the northern Galactic plane, with a high-latitude extension from l = 101 deg to l = 116 deg up to b = 17.5 deg. This is the first extensive polarization survey to present aperture-synthesis data combined with data from single antennas, and the techniques developed to achieve this combination are described. Results: The appearance of the extended polarized emission at 1.4 GHz is dominated by Faraday rotation along the propagation path, and the diffuse polarized sky bears little resemblance to the total-intensity sky. There is extensive depolarization, arising from vector averaging on long lines of sight, from HII regions, and from diffuse ionized gas seen in H-alpha images. Preliminary interpretation is presented of selected polarization features on scales from parsecs (the planetary nebula Sh 2-216) to hundreds of parsecs (a supperbubble GSH 166-01-17) to kiloparsecs (polarized emission in the direction of Cygnus X).

astro-ph.GA↗

arXiv2010

Faraday rotation of the supernova remnant G296.5+10.0: Evidence for a Magnetized Progenitor Wind

We present spectropolarimetric radio images of the supernova remnant (SNR) G296.5+10.0 at frequencies near 1.4 GHz, observed with the Australia Telescope Compact Array. By applying rotation measure (RM) synthesis to the data, a pixel-by-pixel map of Faraday rotation has been produced for the entire remnant. We find G296.5+10.0 to have a highly ordered RM structure, with mainly positive RMs (mean RM of +28 rad/m**2) on the eastern side and negative RMs (mean RM of -14 rad/m**2) on the western side, indicating a magnetic field which is directed away from us on one side and toward us on the other. We consider several possible mechanisms for creating the observed RM pattern. Neither Faraday rotation in foreground interstellar gas nor in a homogeneous ambient medium swept up by the SNR shell can easily explain the magnitude and sign of the observed RM pattern. Instead, we propose that the observed RMs are the imprint of an azimuthal magnetic field in the stellar wind of the progenitor star. Specifically, we calculate that a swept-up magnetized wind from a red supergiant can produce RMs of the observed magnitude, while the azimuthal pattern of the magnetic field at large distances from the star naturally produces the anti-symmetric RM pattern observed. Expansion into such a wind can possibly also account for the striking bilateral symmetry of the SNR's radio and X-ray morphologies.

astro-ph.GA↗

arXiv2008

Science with ASKAP - the Australian Square Kilometre Array Pathfinder

[ABRIDGED VERSION] The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries. The SKA will be 50 times more sensitive than any existing radio facility. A majority of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from 300 MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is aimed squarely in this frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phase-array feed systems on parabolic reflectors. This large field-of-view makes ASKAP an unprecedented synoptic telescope poised to achieve substantial advances in SKA key science. The central core of ASKAP will be located at the Murchison Radio Observatory in inland Western Australia, one of the most radio-quiet locations on the Earth and one of the sites selected by the international community as a potential location for the SKA. Following an introductory description of ASKAP, this document contains 7 chapters describing specific science programmes for ASKAP. The combination of location, technological innovation and scientific program will ensure that ASKAP will be a world-leading radio astronomy facility, closely aligned with the scientific and technical direction of the SKA. A brief summary chapter emphasizes the point, and considers discovery space.

astro-ph↗

arXiv2008

DA495 - an aging pulsar wind nebula

We present a radio continuum study of the pulsar wind nebula (PWN) DA 495 (G65.7+1.2), including images of total intensity and linear polarization from 408 to 10550 MHz based on the Canadian Galactic Plane Survey and observations with the Effelsberg 100-m Radio Telescope. Removal of flux density contributions from a superimposed \ion{H}{2} region and from compact extragalactic sources reveals a break in the spectrum of DA 495 at 1.3 GHz, with a spectral index $α={-0.45 \pm 0.20}$ below the break and $α={-0.87 \pm 0.10}$ above it (${S}_ν\propto{ν^α}$). The spectral break is more than three times lower in frequency than the lowest break detected in any other PWN. The break in the spectrum is likely the result of synchrotron cooling, and DA 495, at an age of $\sim$20,000 yr, may have evolved from an object similar to the Vela X nebula, with a similarly energetic pulsar. We find a magnetic field of $\sim$1.3 mG inside the nebula. After correcting for the resulting high internal rotation measure, the magnetic field structure is quite simple, resembling the inner part of a dipole field projected onto the plane of the sky, although a toroidal component is likely also present. The dipole field axis, which should be parallel to the spin axis of the putative pulsar, lies at an angle of ${\sim}50\degr$ east of the North Celestial Pole and is pointing away from us towards the south-west. The upper limit for the radio surface brightness of any shell-type supernova remnant emission around DA 495 is $Σ_{1 GHz} \sim 5.4 \times 10^{-23}$ OAWatt m$^{-2}$ Hz$^{-1}$ sr$^{-1}$ (assuming a radio spectral index of $α= -0.5$), lower than the faintest shell-type remnant known to date.

astro-ph↗

arXiv2008

Chandra Confirmation of a Pulsar Wind Nebula in DA 495

As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nonthermal nebula 40'' in diameter exhibiting a power-law spectrum with photon index Gamma = 1.6+/-0.3, typical of a pulsar wind nebula. The implied spin-down luminosity of the neutron star, assuming a conversion efficiency to nebular flux appropriate to Vela-like pulsars, is ~10^{35} ergs/s, again typical of objects a few tens of kyr old. Morphologically, the nebular flux is slightly enhanced along a direction, in projection on the sky, independently demonstrated to be of significance in radio polarization observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5'' from the point source, a distance consistent with the sizes of resolved wind termination shocks around many Vela-like pulsars. Finally, we argue based on synchrotron lifetimes in the estimated nebular magnetic field that DA 495 represents a rare pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind, and that this high magnetization factor may account for the nebula's low luminosity.

astro-ph↗

arXiv2007

XMM-Newton, Chandra, and CGPS observations of the Supernova Remnants G85.4+0.7 and G85.9-0.6

We present an XMM-Newton detection of two low radio surface brightness SNRs, G85.4+0.7 and G85.9-0.6, discovered with the Canadian Galactic Plane Survey (CGPS). High-resolution XMM-Newton images revealing the morphology of the diffuse emission, as well as discrete point sources, are presented and correlated with radio and Chandra images. The new data also permit a spectroscopic analysis of the diffuse emission regions, and a spectroscopic and timing analysis of the point sources. Distances have been determined from HI and CO data to be 3.5 +/- 1.0 kpc for SNR G85.4+0.7 and 4.8 +/- 1.6 kpc for SNR G85.9-0.6. The SNR G85.4+0.7 is found to have a temperature of ~12-13 MK and a 0.5-2.5 keV luminosity of ~1-4 x 10^33 D(3.5)^2 erg/s (where D(3.5) is the distance in units of 3.5 kpc), with an electron density n_e of ~0.07-0.16(fD(3.5))^-1/2 cm^-3 (where f is the volume filling factor), and a shock age of ~9-49(fD(3.5))^1/2 kyr. The SNR G85.9-0.6 is found to have a temperature of ~15-19 MK and a 0.5-2.5 keV luminosity of ~1-4 x 10^34 D(4.8)^2 erg/s (where D(4.8) is the distance in units of 4.8 kpc), with an electron density n_e of ~0.04-0.10(fD(4.8))^-1/2 cm^-3 and a shock age of ~12-42(fD(4.8))^1/2 kyr. Based on the data presented here, none of the point sources appears to be the neutron star associated with either SNR.

astro-ph↗

arXiv2007

Radio Polarimetry of the ELAIS N1 Field: Polarized Compact Sources

We present deep polarimetric observations at 1420 MHz of the European Large Area ISO Survey North 1 region (ELAIS N1) as part of the Dominion Radio Astrophysical Observatory Planck Deep Fields project. By combining closely spaced aperture synthesis fields, we image a region of 7.43 square degrees to a maximum sensitivity in Stokes Q and U of 78 microJy/beam, and detect 786 compact sources in Stokes I. Of these, 83 exhibit polarized emission. We find that the differential source counts (log N - log p) for polarized sources are nearly constant down to p > 500 microJy, and that these faint polarized radio sources are more highly polarized than the strong source population. The median fractional polarization is (4.8 +/- 0.7)% for polarized sources with Stokes I flux density between 1 and 30 mJy; approximately three times larger than sources with I > 100 mJy. The majority of the polarized sources have been identified with galaxies in the Spitzer Wide Area Infrared Extragalactic Survey (SWIRE) image of ELAIS N1. Most of the galaxies occupy regions in the IRAC 5.8/3.6 micron vs. 8.0/4.5 micron color-color diagram associated with dusty AGNs, or with ellipticals with an aging stellar population. A few host galaxies have colors that suggests significant PAH emission in the near-infrared. A small fraction, 12%, of the polarized sources are not detected in the SWIRE data. None of the polarized sources in our sample appears to be associated with an actively star-forming galaxy.

astro-ph↗