At this point there are no systematic studies of the X-ray properties of large samples of GPS and CSS sources. The few observations that have been done are nevertheless very interesting and are reviewed below. Observations of a much larger sample with AXAF will be necessary before we understand the X-ray properties of CSS and GPS sources. X-ray observations from the literature are summarized in Table 8. Generalizing from the limited data, it appears that the GPS and CSS quasars can be very luminous in the X-rays (LX ~ 1045-1046 ergs s-1), consistent with them containing a very powerful central engine. On the other hand, the GPS and CSS galaxies tend to be much less luminous than the quasars with luminosities below LX ~ 1044 ergs s-1 and in some cases of order LX ~ 1042 ergs s-1. The large difference between quasar and galaxy X-ray luminosities is consistent with that seen in the large-scale radio sources (see, e.g., Siebert et al. 1996).
|0026+346||GPS||G||7.9×1043||0.2 - 2.0||1||OQQ ?|
|0108+388||GPS||G||< 1.0×1044||0.5 - 4.5||2|
|0134+329||CSS||Q||1.0×1045||0.2 - 2.4||3|
|0237-233||GPS||Q||6.6×1046||0.2 - 4.5||4|
|0420-388||GPS||Q||3.4×1046||2 - 10||5|
|0500+019||GPS||G||4.4×1044||0.2 - 2||1||OQQ|
|0518+165||CSS||Q||1.5×1045||0.2 - 2.4||3|
|0528-250||GPS||Q||< 3.8×1046||0.2 - 4.5||4|
|0538+498||CSS||Q||4.9×1044||0.5 - 4.5||2|
|0636+680||GPS||Q||4.1×1046||2 - 10||5|
|0738+313||GPS||Q||1.4×1045||0.2 - 4.5||4|
|0740+380||CSS||Q||4.4×1045||0.2 - 4.5||4|
|0758+143||CSS||Q||2.0×1045||0.2 - 4.5||4|
|1127-145||GPS||Q||1.1×1046||0.2 - 4.5||4|
|1250+568||CSS||Q||2.2×1044||0.2 - 4.5||4|
|1416+067||CSS||Q||9.7×1045||0.2 - 4.5||4|
|1442+101||GPS||Q||8.8×1046||0.2 - 4.5||4|
|1328+254||CSS||Q||2.8×1045||0.2 - 2.4||3|
|1328+307||CSS||Q||4.7×1044||0.2 - 2.4||3|
|1345+125||GPS||G||1.7×1042||0.2 - 2||6||marginal detection ?|
|1358+624||GPS||G||< 1.8×1044||0.5 - 4.5||2|
|1404+286||GPS||Q||1.0×1042||0.3 - 2.5||7|
|1458+718||CSS||Q||3.0×1045||0.2 - 2.4||3|
|1517+204||CSS||G||< 4.3×1044||0.7 - 2.0||8|
|1614+051||GPS||Q||2.7×1046||0.2 - 4.5||4|
|1637+626||CSS||G||< 6.5×1043||0.7 - 2.0||8|
|2000-330||GPS||Q||5.2×1046||2 - 10||5|
|2106-409||GPS||G||2.9×1045||0.2 - 2||1||OQQ|
|2126-158||GPS||Q||3.9×1047||2 - 10||5||X-ray absorption|
|2223+210||GPS||Q||1.0×1047||0.2 - 4.5||4|
|2352+495||GPS||G||< 1.4×1042||0.2 - 2||6|
NOTES. - X-ray observations from the literature. Luminosities are converted to the distance scale used in this review.
REFERENCES. - (1) Kollgaard et al. 1995; (2) Bloom & Marscher 1991; (3) Prieto 1996; (4) Wilkes et al. 1994; (5) Elvis et al. 1994; (6) O'Dea et al. 1996; (7) Zhang & Marscher 1994; (8) Crawford & Fabian 1996.
There is evidence for an additional column of X-ray absorbing material (in excess of the Galactic value) in some GPS quasars (Elvis et al. 1994) and the GPS broad-line radio galaxy OQ 208 (Zhang & Marscher 1994). This extra absorption may be associated with high-redshift quasars in general and not just with GPS sources. Elvis et al. estimate the extra column density to be of order 1022 cm-2. Possible locations for the material include (1) intervening Ly systems, (2) cluster cooling flows, and (3) material associated with the quasar. Elvis et al. (1994) examine the radio and optical properties of the quasars with extra absorption and suggest that the absorbing material is associated with the quasar. If this is the case, then the absorption may take place in circumnuclear gas on the subkiloparsec scale. Baker, Hunstead, & Brinkmann (1995) detect X-rays from CSS quasars only one-third as often as non-CSS quasars in the Molonglo quasar sample. This could be due to larger absorbing columns in the CSS quasars or to a difference in the quasar spectra. Baker & Hunstead (1996) find associated absorption-line systems to be extremely common in their CSS quasars, suggesting the presence of large columns associated with the quasar.
O'Dea et al. (1996b) obtained sensitive ROSAT observations of two GPS galaxies, 1345+125 and 2352+495. The 3 upper limits to the X-ray luminosity are about LX < 3 × 1042 ergs s-1. The X-ray luminosities are too low to be consistent with emission from a typical Abell cluster but are consistent with the X-ray luminosity of early-type galaxies (LX ~ 1039-1041 ergs s-1, Forman, Jones, & Tucker 1985) and of groups or poor clusters of galaxies with central dominant galaxies (LX ~ 1041-1043 ergs s-1; see, e.g., Kriss, Cioffi, & Canizares 1983). The optical fields around 1345+125 (Hutchings, Johnson, & Pyke 1988; Baum et al. 1988; Stanghellini et al. 1993) and 2352+495 (O'Dea et al. 1990a) are consistent with such a sparse environment.
O'Dea et al. use the X-ray constraints to show that the pressure from a hot ISM in the host galaxies is orders of magnitude too low to confine the radio sources. If the source advance is not slowed by collisions with clouds (O'Dea et al. 1991; Carvalho 1994, 1998; De Young 1991; Balsara 1991) and the lobes are in ram pressure balance with the hot ISM, then the advance speed (va) is given by
where Pl is the lobe pressure in dyn cm-2 and n is the ambient density in cm-3 (cf. Readhead et al. 1996b). This suggests that the radio sources are not confined and might expand to become large-scale radio sources (see, e.g., Phillips & Mutel 1982; Carvalho 1985; Hodges & Mutel 1987; De Young 1993; Fanti et al. 1995; Begelman 1996; Readhead et al. 1996a, 1996b; O'Dea & Baum 1997). Alternatively, the radio sources could be confined by another component of the ISM, e.g., dense, cold gas. O'Dea et al. also show that the X-ray luminosity in 1345+125 and 2352+495 is too low to be consistent with large cooling flows in the host galaxies and/or surrounding ICM. A conservative upper limit to the mass accretion rate is a few M yr-1.