Radio Galaxy Zoo Talk

The Link Between Morphology and Structure of Brightest Cluster Galaxies: Automatic Identification of cDs

  • JeanTate by JeanTate

    The Link Between Morphology and Structure of Brightest Cluster Galaxies: Automatic Identification of cDs (arXiv:1501.06352), by Dongyao Zhao, Alfonso Aragón-Salamanca, Christopher J. Conselice:

    We study a large sample of 625 low-redshift brightest cluster galaxies (BCGs) and link their morphologies to their structural properties. We derive visual morphologies and find that ~57% of the BCGs are cD galaxies, ~13% are ellipticals, and ~21% belong to the intermediate classes mostly between E and cD. There is a continuous distribution in the properties of the BCG's envelopes, ranging from undetected (E class) to clearly detected (cD class), with intermediate classes (E/cD and cD/E) showing the increasing degrees of the envelope presence. A minority (~7%) of BCGs have disk morphologies, with spirals and S0s in similar proportions, and the rest (~2%) are mergers. After carefully fitting the galaxies light distributions by using one-component (Sersic) and two-component (Sersic+Exponential) models, we find a clear link between the BCGs morphologies and their structures and conclude that a combination of the best-fit parameters derived from the fits can be used to separate cD galaxies from non-cD BCGs. In particular, cDs and non-cDs show very different distributions in the Re--RFF plane, where Re is the effective radius and RFF (the residual flux fraction) measures the proportion of the galaxy flux present in the residual images after subtracting the models. In general, cDs have larger Re and RFF values than ellipticals. Therefore we find, in a statistically robust way, a boundary separating cD and non-cD BCGs in this parameter space. BCGs with cD morphology can be selected with reasonably high completeness (~75%) and low contamination (~20%). This automatic and objective technique can be applied to any current or future BCG sample with good quality images.

    "low-redshift" means between 0.02 and 0.10, and the 625 BCGs come from "the C4 cluster catalogue (Miller et al. 2005) extracted from the Sloan Digital Sky Survey (SDSS; York et al. 2000) third data release spectroscopic sample". So there are certainly many other BCG in this redshift range, even in the SDSS (DR12) footprint.

    This is very cool (my bold):

    The 625 BCGs in L07 sample were visually classified by careful inspection of the SDSS images.[...] Finally the BCGs were classified into three main types: 414 cDs, including pure cD (356), cD/E (53) and cD/S0 (5); 155 ellipticals, including pure E (80), E/cD (72), and E/S0 (3); 46 disk galaxies, containing spirals (24) and S0s (22). [...] There are also 10 BCGs undergoing major mergers, but we will not discuss them in this paper in any detail.

    Finally, "Table A1 contains the main properties of the BCGs discussed in this paper. The full table is published electronically". Sadly, I cannot find the electronic publication (the table, that is).

    Posted

  • c_cld by c_cld

    The 625 BCGs in L07 are listed in

    http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/MNRAS/379/867

    waiting for the whole classification by Dongyao Zhao et al.

    Posted

  • c_cld by c_cld

    Table1

    ID3,objID,ra,dec

    1001,1237655126093332896,208.276657209611,5.14973053286066

    1002,1237654606399340792,159.777581192866,5.2097771635863

    1004,1237651737906380966,184.421355252373,3.65584561912355

    1013,1237648704059342955,227.107327849394,-0.266261197444681

    1025,1237648720145350665,153.409481650162,-0.925411821689492

    1027,1237648721235935344,191.926942575495,-0.137131041149662

    1036,1237671762638340300,192.308657277828,-1.68739447128561

    1039,1237658491208597518,186.878088738793,8.82455434973549

    1042,1237662266463879296,228.808799288854,4.38621614871618

    1044,1237650371562111204,194.672890001467,-1.7614548217834

    1048,1237671958055616674,205.540237318414,2.22723579724928

    1058,1237650370488828041,195.719060767421,-2.51634180648893

    1061,1237662266463617118,228.22070087208,4.51400436223867

    1066,1237655499737792597,202.795112486473,-1.73027191163332

    1069,1237654605873348675,184.718168622709,5.24566672253103

    1075,1237648721219092791,153.437078981193,-0.120223662590781

    1126,1237671264422264969,192.516071856564,-1.54040026726414

    1276,1237654606409564368,183.271262352779,5.68967704046082

    1283,1237658300056600899,125.745444465212,4.29911796115212

    1389,1237648722314264707,202.337877061663,0.749689332713676

    1456,1237651753470525612,173.336231150235,2.19905793873818

    1460,1237654605869351109,175.554112909368,5.25169075965349

    2002,1237652946914443286,358.556929002037,-10.4190219346287

    2013,1237652948530167954,10.4602114396463,-9.30318352091331

    2035,1237657190370181178,4.17731046508118,-0.445436568929728

    2050,1237666215143473303,17.5131978662842,13.978142119907

    2074,1237652934032097563,314.975446645091,-7.26075871546814

    2085,1237656536975016057,334.197431723708,-9.72478659904446

    2109,1237656495113568568,359.829859593888,14.6710708822766

    2214,1237656495097184890,321.599490141602,10.7775224712259

    3004,1237671939804561476,258.119946070518,64.0607482946166

    3012,1237655474508857360,255.677048104433,34.0599860693685

    3028,1237655108919033953,204.034683442159,59.2063960473927

    3084,1237657401335939192,118.360815960763,29.3594451118144

    3094,1237659327107170684,254.93311637237,32.6153231637831

    3283,1237651539775651910,135.322533603079,58.2797550365887

    3332,1237655108359880795,124.471394203693,40.72639020832

    3347,1237657401336725620,119.679756703026,30.7737751371575

    Posted

  • JeanTate by JeanTate

    Thanks C_cld. 😃

    Posted