1998A&A...334..459B

Query : 1998A&A...334..459B

1998A&A...334..459B - Astronomy and Astrophysics, volume 334459-472 (1998/6-2)

On the evolutionary behaviour of BL Lac objects.

BADE N., BECKMANN V., DOUGLAS N.G., BARTHEL P.D., ENGELS D., CORDIS L., NASS P. and VOGES W.

Abstract (from CDS):

We present a new well defined sample of BL Lac objects selected from the ROSAT All-Sky Survey (RASS). The sample consists of 39 objects with 35 forming a flux limited sample down to fX(0.5-2.0keV)=8x10–13ergs/cm2/s; redshifts are known for 33 objects (and 31 of the complete sample). X-ray spectral properties were determined for each object individually with the RASS data. The luminosity function of RASS selected BL Lac objects is compatible with results provided by objects selected with the Einstein observatory, but the RASS selected sample contains objects with luminosities at least tenfold higher. Our analysis confirms the negative evolution for X-ray selected BL Lac objects found in a sample by the Einstein observatory, the parameterization provides similar results. A subdivision of the sample into halves according to the X-ray to optical flux ratio yielded unexpected results. The extremely X-ray dominated objects have higher redshifts and X-ray luminosities and only this subgroup shows clear signs of strong negative evolution. The evolutionary behaviour of objects with an intermediate spectral energy distribution between X-ray and radio dominated is compatible with no evolution at all. Consequences for unified schemes of X-ray and radio selected BL Lac objects are discussed. We suggest that the intermediate BL Lac objects are the basic BL Lac population. The distinction between the two subgroups can be explained if extremely X-ray dominated BL Lac objects are observed in a state of enhanced X-ray activity.

Abstract Copyright: ∼

Journal keyword(s): galaxies: active - BL Lacertae objects: general - X-rays: galaxies

Simbad objects: 40

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Number of rows : 40
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 RX J0809.6+3455 BLL 08 09 38.8872832824 +34 55 37.248843504   18.38 17.42 12.6   ~ 112 1
2 RX J0809.8+5218 BLL 08 09 49.1868285744 +52 18 58.249938744   16.11 15.59 14.6   ~ 302 1
3 RX J0832.8+3300 BLL 08 32 51.4560108888 +33 00 10.878600168   21.50 20.86 19.8   ~ 24 0
4 RX J0909.8+3105 BLL 09 09 53.2839851256 +31 06 03.167783208   18.74 17.98     ~ 61 0
5 Ton 397 BLL 09 15 52.4015550384 +29 33 24.042671532   16.79 16.39 16.085   ~ 238 1
6 RX J0916.8+5238 BLL 09 16 51.9350409624 +52 38 28.331223072   19.02 18.10 15   ~ 82 1
7 RX J0930.6+4950 BLL 09 30 37.5737660328 +49 50 25.549611036   18.81 18.25 17.3   ~ 128 0
8 RX J1008.1+4705 BLL 10 08 11.4282574752 +47 05 21.453100692   20.22 19.40 18   ~ 35 0
9 RX J1015.0+4926 BLL 10 15 04.1396533776 +49 26 00.706055496   16.56 16.15 14.58   ~ 400 3
10 RX J1031.3+5053 BLL 10 31 18.5251007784 +50 53 35.817278064   17.25 16.98 16.3   ~ 210 2
11 RX J1058.6+5628 BLL 10 58 37.7276569824 +56 28 11.207405028   16.80 16.31 14.58   ~ 232 1
12 RX J1111.5+3452 BLL 11 11 30.8991225240 +34 52 03.412837704   19.96 19.52 19.3   ~ 25 0
13 Z 334-43 BLL 11 36 26.4090783600 +70 09 27.309071232   15.16 14.49 10.51   ~ 394 1
14 HS 1133+6753 BLL 11 36 30.0868711488 +67 37 04.345988232   18.19 17.45 15.3   ~ 161 1
15 Ton 605 HB* 12 16 53.6748432768 +30 04 08.692883544   16.110 15.98     B 223 0
16 RX J1217.8+3007 BLL 12 17 52.0819904040 +30 07 00.634936872   16.07 15.62 13.47   G7 516 1
17 PG 1218+304 BLL 12 21 21.9426947832 +30 10 37.158534012   16.50 15.85 15.7   ~ 497 1
18 RX J1230.2+2518 BLL 12 30 14.0893292232 +25 18 07.136022996   15.6   14.78   ~ 177 1
19 QSO B1229+6430 BLL 12 31 31.3949261640 +64 14 18.280701600   18.36 17.62 14.3   ~ 160 2
20 RX J1237.0+3020 BLL 12 37 05.6098555320 +30 20 04.993401156   20.35 19.93 19.2   ~ 24 0
21 RX J1237.6+6258 BLL 12 37 39.0753390528 +62 58 42.801146328   18.89 18.25 17   ~ 116 0
22 RX J1241.6+3440 BLL 12 41 41.3827131720 +34 40 31.005349824   20.21 19.70 19.4   DC 35 0
23 LB 2449 BLL 12 48 18.7847605224 +58 20 28.717260720   16.10 15.78 15.19   ~ 215 1
24 RX J1302.9+5056 BLL 13 02 55.3449487680 +50 56 18.276920808   20.05 19.65 20.6   ~ 22 0
25 ICRF J132400.9+573916 BLL 13 24 00.9062108592 +57 39 16.343433540     17.30 14.1   ~ 35 1
26 RX J1326.2+2933 BLL 13 26 14.9932019160 +29 33 30.967995924     18.34     ~ 38 0
27 RX J1353.4+5601 BLL 13 53 28.0474623240 +56 00 56.986350984   19.31 18.92 16.4   ~ 43 0
28 RX J1404.8+6554 BLL 14 04 49.5814752144 +65 54 31.557003840   19.53 18.88 18.7   ~ 64 0
29 RX J1410.5+6100 BLL 14 10 30.8510555520 +61 00 12.775184496   20.30 19.45 18.7   ~ 32 0
30 RX J1422.6+5801 BLL 14 22 38.8822521768 +58 01 55.514940024   18.49 18.15 17.7   ~ 86 0
31 RX J1436.9+5639 BLL 14 36 57.7190885904 +56 39 24.859811736   18.92 18.51 17.6   ~ 83 0
32 RX J1444.5+6336 BLL 14 44 34.9068259224 +63 36 05.984137260   20.76 19.67 18.6   ~ 63 0
33 RX J1451.4+6354 BLL 14 51 27.7354582032 +63 54 19.249726032     19.60 19   ~ 37 1
34 NVSS J145608+504836 BLL 14 56 08.11972063 +50 48 36.3006926       21.80   ~ 43 1
35 RX J1458.4+4832 BLL 14 58 27.3601381032 +48 32 45.985282260   21.12 20.42 19.2   ~ 21 0
36 RX J1517.7+6525 BLL 15 17 47.5882526184 +65 25 23.285593704       16.7   ~ 131 1
37 RX J1535.0+5320 BLL 15 35 00.7962236712 +53 20 37.302992988   19.18 18.75 18.8   ~ 73 1
38 RX J1631.4+4216 BLL 16 31 24.7071049968 +42 17 02.366014416   19.82 19.29 18.4   ~ 29 0
39 RX J1644.3+4546 BLL 16 44 19.9733510880 +45 46 44.350987764   19.44 18.50 15.2   ~ 70 1
40 ZW I 187 BLL 17 28 18.6242294352 +50 13 10.469553996   16.55 15.97 12.95   ~ 396 1

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