1. Radio Observations of Nearby HST BL Lacs
Marcello Giroletti
(IRA & Univ. of Bologna)
Gabriele Giovannini
Greg B. Taylor
(NRAO, Socorro)

2. Outline Introduce the sample Present radio observations and maps
Show preliminary analysis
Summarize the results

3. A sample of nearby BL Lacs
Which?
Falomo et al. 2000, ApJ 542, 731
30 objects with z<0.2 (out of a 110 sample)
not complete but homogeneous
all fully resolved
“normal” elliptical host galaxies
(of course) Central Compact Cores
3 optical jets: , 3C 371,
Why?
high linear resolution - VLBI, HST…
nearby ~ low luminosity ~ HBL
basically different and “border-line” population

4. A comparison to 1 Jy sample...
<Log P1.4 GHz> = /- 0.9
<Log P1.4 GHz> = /- 0.6
few objects well studied in radio (less than 50% have VLBI or VLA)

5. Radio observations VLA @1.4 GHz: VLBA @5 GHz: 15 hrs/15 sources
A conf., 10 hrs/19 sources
C conf., 5 hrs/9 sources
GHz: 15 hrs/15 sources
GHz: 12 hrs/6 sources
GHz: 12 hrs/2 sources

6. 0706+591 z = 0.125 VLA image, A conf., 1.4 GHz peak = 63 mJy/beam
total = 161 mJy
PA = 128°
z = 0.125
peak = 33 mJy/beam
total = 44 mJy
PA = 205°
VLBA image, 5 GHz

7. 1215+303 z = 0.130 VLA image, from FIRST survey peak = 377 mJy/beam
total = 590 mJy
PA = ???
z = 0.130
peak = 294 mJy/beam
total = 350 mJy
PA = 150°
EVN+MERLIN image, 5 GHz

8. (see poster by Rector et al.)
z = 0.044
VLA C-conf
VLA A-conf
GHz
(see poster by Rector et al.)

9. Core Dominance From radio data: Dominant cores and one sided jets.
we estimated b, q from the correlation between core and total radio power (e.g. Giovannini et al. 2001)
typical values of b, q for BL Lacs: b > 0.9, q < 25°.

10. Correlations: Opt vs Radio core
Chiaberge et al. 2000

11. Summary 30 objects sample; all with images on pc/kpc resolution
many different morphology / possible dependence on total power
luminosities consistent with known correlations
work in progress on more correlations, environment, web site