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Radio Observations of Nearby HST BL Lacs

Radio Observations of Nearby HST BL Lacs. Marcello Giroletti (IRA & Univ. of Bologna) Gabriele Giovannini (IRA & Univ. of Bologna) Greg B. Taylor (NRAO, Socorro). Outline. Introduce the sample Present radio observations and maps Show preliminary analysis Summarize the results.

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Radio Observations of Nearby HST BL Lacs

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  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 • 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: 0521-36, 3C 371, 2201+044 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> = 26.8 +/- 0.9 • <Log P1.4 GHz> = 24.8 +/- 0.6 • few objects well studied in radio (less than 50% have VLBI or VLA)

  5. Radio observations • VLA @1.4 GHz: • A conf., 10 hrs/19 sources • C conf., 5 hrs/9 sources • VLBA @5 GHz: 15 hrs/15 sources • EVN @1.6 GHz: 12 hrs/6 sources • EVN+MERLIN @5 GHz: 12 hrs/2 sources

  6. VLA image, A conf., 1.4 GHz • peak = 63 mJy/beam • total = 161 mJy • PA = 128° • 0706+591 • 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 = ??? 1215+303 z = 0.130 • peak = 294 mJy/beam • total = 350 mJy • PA = 150° • EVN+MERLIN image, 5 GHz

  8. 2344+514 z = 0.044 VLA C-conf VLA A-conf VLBA @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 > 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

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