Radio Galaxy Zoo Talk


  • nico775 by nico775 translator

    a big one ???


  • JeanTate by JeanTate in response to nico775's comment.

    It's a very nice, classic AGN+jets+lobes source!

    It's not clear to me which elliptical galaxy is the core - the center of the radio core seems ~midway between two, but maybe I'm just not measuring it right - but SDSS J104434.63+144204.0 has a spectrum, so I'll go with that! That galaxy has a redshift of 0.155 - so it's quite close (compared with most of the classic radio sources we've been finding, here in RGZ), and so the size is more apparent than real (it's not a giant, for example*). Although the SDSS spectro pipeline classifies it as merely 'GALAXY', it's got all the usual suspect emission lines, and H-alpha seems somewhat broadened ... in short, the spectrum of an AGN (perhaps a rather quiet one). Here's the SDSS field, centered on this galaxy:

    enter image description here

    The other galaxy which could be the core is SDSS J104435.43+144200.7, just to the left.

    ETA: In following up on this, using NED, I came across Lin+2010, "On the Populations of Radio Galaxies with Extended Morphology at z < 0.3":

    Extended extragalactic radio sources have traditionally been classified into Fanaroff & Riley (FR) I and II types, based on the ratio rs of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source (rs ≡ S/T). In this paper, we examine the distribution of various physical properties as a function of rs of 1040 luminous (L >~ L *) extended radio galaxies (RGs) at z < 0.3 selected with well-defined criteria from the SDSS, NVSS, and FIRST surveys. About 2/3 of the RGs are lobe dominated (LD) and 1/3 have prominent jets. If we follow the original definition of the FR types, i.e., a division based solely on rs , FR I and FR II RGs overlap in their host galaxy properties. However, the rare LD sources with rs >~ 0.8 and [O III] λ5007 line luminosity >106 L sun are markedly different on average from the rest of the RGs, in the sense that they are hosted in lower mass galaxies, live in relatively sparse environments, and likely have higher accretion rates onto the central supermassive black hole (SMBH). Thus, these high emission line luminosity, high-rs LD RGs, and the rest of RGs form a well-defined dichotomy. Motivated by the stark differences in the nuclear emission line properties of the RG subsamples, we suggest that the accretion rate onto the SMBH may play the primary role in creating the different morphologies. At relatively high accretion rates, the accretion system may produce powerful jets that create the "classical double" morphology (roughly corresponding to the LD sources with rs >~ 0.8 and emission lines); at lower accretion rates, the jets from a radiatively inefficient accretion flow generate radio lobes without apparent "hot spots" at the edge (corresponding to the majority of LD sources). At slightly lower accretion rates and in galaxies with dense galactic structure, sources with prominent jets result. It is possible that while the high accretion rate systems could affect sub-Mpc scale environments, the jets from lower accretion rate systems may efficiently suppress activity within the host galaxies.

    Which goes a long way to answering a question I've been meaning to ask for some time now. So, a HUGE thank you to you, nico775 😄

    *but no, I didn't do the calculation (feeling lazy this morning)


  • nico775 by nico775 translator