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|Title:||Restarting radio activity and dust emission in radio-loud broad absorption line quasars||Authors:||Bruni, Gabriele
Mack, K. -H.
Montenegro-Montes, F. M.
González-Serrano, J. I.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||582||First Page:||A9||Abstract:||Context. Broad absorption line quasars (BAL QSOs) are objects that show absorption from relativistic outflows that have velocities up to 0.2c. In about 15% of quasars, these manifest as absorption troughs on the blue side of UV emission lines, such as C iv and Mg ii. The launching mechanism and duration of these outflows is not clear yet. <BR /> Aims: In this work, we complement the information collected in the cm band for our previously presented sample of radio loud BAL QSOs (25 objects with redshifts 1.7 < z < 3.6) with new observations in the m and mm bands. Our aim is to verify the presence of old, extended radio components in the MHz range and probe the emission of dust (linked to star formation) in the mm domain. <BR /> Methods: We observed 5 sources from our sample, which already presented hints of low-frequency emission, with the GMRT at 235 and 610 MHz. Another 17 sources (more than half the sample) were observed with bolometer cameras at IRAM-30 m (MAMBO2, 250 GHz) and APEX (LABOCA and SABOCA, 350 and 850 GHz, respectively). <BR /> Results: All sources observed with the GMRT present extended emission on a scale of tens of kpc. In some cases these measurements allow us to identify a second component in the SED at frequencies below 1.4 GHz, beyond the one already studied in the GHz domain. In the mm band, only one source shows emission clearly ascribable to dust, detached from the synchrotron tail. Upper limits were obtained for the remaining targets. <BR /> Conclusions: These findings confirm that BAL QSOs can also be present in old radio sources or even in restarting ones where favourable conditions for the outflow launching or acceleration are present. A suggestion that these outflows could be precursors of the jet comes from the possibility that ~70% of our sample is in a GigaHertz Peaked Spectrum (GPS) or Compact Steep Spectrum (CSS)+GPS phase. This would confirm the idea proposed by other authors that these outflows could be recollimated to form the jet. Compared with previous works in the literature, dust emission seems to be weaker than what is expected in "normal" QSOs (both radio loud and radio quiet ones), suggesting that a feedback mechanism could inhibit star formation in radio-loud BAL QSOs.||Acknowledgments:||Part of this work was supported by a grant of the Italian Programme for Research of National Interest (PRIN No. 18/2007, PI: K.-H. Mack) The authors acknowledge financial support from the Spanish Ministerio de Ciencia e Innovación under project AYA2008-06311-C02-02. We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory. This work is partly based on observations carried out with the IRAM-30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).||URI:||http://hdl.handle.net/20.500.12386/26489||URL:||https://www.aanda.org/articles/aa/abs/2015/10/aa26596-15/aa26596-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201526596||Bibcode ADS:||2015A&A...582A...9B||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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