The Phoenix Deep Survey: X-ray properties of faint radio sources

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dc.creatorGeorgakakis, A.
dc.creatorHopkins, A. M.
dc.creatorSullivan, M.
dc.creatorAfonso, J.
dc.creatorGeorgantopoulos, I.
dc.creatorMobasher, B.
dc.creatorCram, L. E.
dc.date2003-07-22
dc.date.accessioned2026-07-07T12:16:22Z
dc.date.available2026-07-07T12:16:22Z
dc.descriptionIn this paper we use a 50ks XMM-Newton pointing overlapping with the Phoenix Deep Survey, a homogeneous radio survey reaching muJy sensitivities, to explore the X-ray properties and the evolution of star-forming galaxies. UV, optical and NIR photometry is available and is used to estimate photometric redshifts and spectral types for radio sources brighter than R=21.5mag (total of 82). Sources with R<21.5mag and spiral galaxy SEDs (34) are grouped into two redshift bins with a median of z=0.240 and 0.455 respectively. Stacking analysis for both the 0.5-2 and 2-8keV bands is performed on these subsamples. A high confidence level signal (>3.5sigma) is detected in the 0.5-2keV band corresponding to a mean flux of ~3e-16cgs for both subsamples. This flux translates to mean luminosities of ~5e40 and 1.5e41cgs for the z=0.240 and 0.455 subsamples respectively. Only a marginally significant signal (2.6sigma) is detected in the 2-8keV band for the z=0.455 subsample. We argue that the stacked signal above is dominated by star-formation. The mean L_X/L_B ratio and the mean L_X of the two subsamples are found to be higher than optically selected spirals and similar to starbursts. We also find that the mean L_X and L_1.4 of the faint radio sources studied here are consistent with the L_X-L_1.4 correlation of local star-forming galaxies. Moreover, the X-ray emissivity of sub-mJy sources to z~0.3 is found to be elevated compared to local HII galaxies. The observed increase is consistent with L_X evolution of the form (1+z)^3. Assuming that our sample is indeed dominated by starbursts this is direct evidence for evolution of such systems at X-ray wavelengths. Using an empirical L_X to SFR conversion we estimate a global SFR density at z~0.3 of \~0.029M_o/yr/Mpc in agreement with previous studies.
dc.description12 pages, 6 figures, accepted for publication in MNRAS
dc.identifierhttps://arxiv.org/abs/astro-ph/0307377
dc.identifierhttp://arxiv.org/abs/astro-ph/0307377
dc.identifierMon.Not.Roy.Astron.Soc.345:939,2003
dc.identifierdoi:10.1046/j.1365-8711.2003.07015.x
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/211779
dc.subjectAstrophysics
dc.titleThe Phoenix Deep Survey: X-ray properties of faint radio sources
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