Radio Observations of Nearby HST BL Lacs

1
Radio Observations of Nearby HST BL Lacs
Marcello Giroletti (IRA Univ. of
Bologna) Gabriele Giovannini (IRA Univ. of
Bologna) Greg B. Taylor (NRAO, Socorro)
2
Outline

1. Introduce the sample
2. Present radio observations and maps
3. Show preliminary analysis
4. Summarize the results

3
A sample of nearby BL Lacs

• Which?
• Falomo et al. 2000, ApJ 542, 731
• 30 objects with zlt0.2 (out of a 110 sample)
• not complete but homogeneous
• all fully resolved
• normal elliptical host galaxies
• (of course) Central Compact Cores
• 3 optical jets 0521-36, 3C 371, 2201044
• Why?
• high linear resolution - VLBI, HST
• nearby low luminosity HBL
• basically different and border-line population

4
A comparison to 1 Jy sample...

• ltLog P1.4 GHzgt 26.8 /- 0.9
• ltLog P1.4 GHzgt 24.8 /- 0.6
• few objects well studied in radio (less than 50
  have VLBI or VLA)

5
Radio observations

• VLA _at_1.4 GHz
• A conf., 10 hrs/19 sources
• C conf., 5 hrs/9 sources
• VLBA _at_5 GHz 15 hrs/15 sources
• EVN _at_1.6 GHz 12 hrs/6 sources
• EVNMERLIN _at_5 GHz 12 hrs/2 sources

6
VLA image, A conf., 1.4 GHz peak 63
mJy/beam total 161 mJy PA 128

• 0706591
• z 0.125

peak 33 mJy/beam total 44 mJy PA 205 VLBA
image, 5 GHz
7
VLA image, from FIRST survey peak 377 mJy/beam
total 590 mJy PA ???
1215303 z 0.130
peak 294 mJy/beam total 350 mJy PA
150 EVNMERLIN image, 5 GHz
8
2344514 z 0.044
VLA C-conf
VLA A-conf
VLBA _at_5 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 gt 0.9, q lt
  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