Abstract
Chandra X-ray observations of the high redshift (z =1.532) radio-loud quasar 3C270.1 in 2008 February show the nucleus to have a power-law spectrum, Gamma = 1.66 +/- 0.08, typical of a radio-loud quasar, and a marginally-detected Fe Kalpha emission line. The data also reveal extended X-ray emission, about half of which is associated with the radio emission from this source. The southern emission is co-spatial with the radio lobe and peaks at the position of the double radio hotspot. Modeling this hotspot including Spitzer upper limits rules out synchrotron emission from a single power-law population of electrons, favoring inverse-Compton emission with a field of ~11nT, roughly a third of the equipartition value. The northern emission is concentrated close to the location of a 40 deg. bend where the radio jet is presumed to encounter external material. It can be explained by inverse Compton emission involving Cosmic Microwave Background photons with a field of ~3nT, roughly a factor of nine below the equipartition value. The remaining, more diffuse X-ray emission is harder (HR=-0.09 +/- 0.22). With only 22.8+/-5.6 counts, the spectral form cannot be constrained. Assuming thermal emission with a temperature of 4 keV yields an estimate for the luminosity of 1.8E44 erg/s, consistent with the luminosity-temperature relation of lower-redshift clusters. However deeper Chandra X-ray observations are required to delineate the spatial distribution, and better constrain the spectrum of the diffuse emission to verify that we have detected X-ray emission from a high-redshift cluster.
Highlights
With the aim of quantifying the orientation dependence of the observed properties of quasars, we have embarked on multiwavelength observations of high-redshift (1 z 2) radio sources with Chandra, Spitzer, Herschel, and ground-based observatories
The net counts were extracted from a circle with a 1.7 radius centered on α = 12 20 33.91, δ = +33 43 07.25, which includes the cluster of counts in this region and aligns well with the position of the double radio hot spot
Counts were extracted from a circular region, radius 1.25, centered on α = 12:20:33.74, δ = 33:43:15.4, selecting the cluster of events apparently associated with the radio emission in this region of sky
Summary
With the aim of quantifying the orientation dependence of the observed properties of quasars, we have embarked on multiwavelength observations of high-redshift (1 z 2) radio sources with Chandra, Spitzer, Herschel, and ground-based observatories. Emission due to upscattering of radio photons within the radio hot spots (synchrotron self-Compton, SSC; Hardcastle et al 2004), or iC upscattering of external radio photons in the extended lobes, most likely from the cosmic microwave background (iC/CMB; Croston et al 2005) The latter will be more luminous for larger radio-emitting structures and at higher redshift due to the higher energy density of the CMB. Luminous high-redshift radio sources occur in massive galaxies and so, according to the hierarchical paradigm, form at peaks in the dark matter density They are beacons for high-density regions in the early universe and for high-redshift clusters and groups, very few of which are yet known.
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