The Link Between Morphology and Structure of Brightest Cluster Galaxies: Automatic Identification of cDs
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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
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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
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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
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by JeanTate
Thanks C_cld. 😃
Posted