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J/ApJ/806/268   Cheshire Cat galaxies: redshifts and magnitudes   (Irwin+, 2015)

The Cheshire Cat gravitational lens: the formation of a massive fossil group. Irwin J.A., Dupke R., Carrasco E.R., Maksym W.P., Johnson L., White III R.E. <Astrophys. J., 806, 268 (2015)> =2015ApJ...806..268I (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Gravitational lensing ; Photometry, SDSS ; Redshifts Keywords: galaxies: clusters: individual: SDSS J1038+4849 - gravitational lensing: strong - X-rays: galaxies: clusters Abstract: The Cheshire Cat is a relatively poor group of galaxies dominated by two luminous elliptical galaxies surrounded by at least four arcs from gravitationally lensed background galaxies that give the system a humorous appearance. Our combined optical/X-ray study of this system reveals that it is experiencing a line of sight merger between two groups with a roughly equal mass ratio with a relative velocity of ∼1350 km/s. One group was most likely a low-mass fossil group, while the other group would have almost fit the classical definition of a fossil group. The collision manifests itself in a bimodal galaxy velocity distribution, an elevated central X-ray temperature and luminosity indicative of a shock, and gravitational arc centers that do not coincide with either large elliptical galaxy. One of the luminous elliptical galaxies has a double nucleus embedded off-center in the stellar halo. The luminous ellipticals should merge in less than a Gyr, after which observers will see a massive 1.2-1.5x1014 M fossil group with an Mr=-24.0 brightest group galaxy at its center. Thus, the Cheshire Cat offers us the first opportunity to study a fossil group progenitor. We discuss the limitations of the classical definition of a fossil group in terms of magnitude gaps between the member galaxies. We also suggest that if the merging of fossil (or near-fossil) groups is a common avenue for creating present-day fossil groups, the time lag between the final galactic merging of the system and the onset of cooling in the shock-heated core could account for the observed lack of well-developed cool cores in some fossil groups. Description: The optical observations (imaging and spectroscopy) were performed with the Gemini Multi-Object Spectrograph (hereafter GMOS; Hook et al. 2004PASP..116..425H) at the Gemini North Telescope in Hawaii, in queue mode, as part of the program GN-2011A-Q-25. The direct images were recorded through the r' and i' filters during the night of 2011 January 4, in dark time, with seeing median values of 0.8" and 0.9" for the r' and i' filters, respectively. The night was not photometric. Three 300 s exposures (binned by two in both axes, with pixel scale of 0.146") were observed in each filter. Offsets between exposures were used to take into account the gaps between the CCDs (37 un-binned pixels) and for cosmic ray removal. Objects: ---------------------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------------------- 10 38 43.58 +48 49 17.7 Cheshire Cat = [KAA2009] SDSS J1038+4849 ---------------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 87 98 Redshifts and Magnitudes of the Observed Galaxies
See also: V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015) J/AJ/137/3942 : Fossil galaxy groups (La Barbera+, 2009) J/ApJ/833/194 : Group of galaxies in gravitational lens fields (Wilson+, 2016) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1 A1 --- Group [ABC] Galaxy's group (1) 3- 6 A4 --- ID Source Extractor galaxy identifier (2) 8- 9 A2 --- Other Other ID 11- 12 I2 h RAh Hour of the Right Ascension (J2000) 14- 15 I2 min RAm Minute of the Right Ascension (J2000) 17- 22 F6.3 s RAs Second of the Right Ascension (J2000) 24 A1 --- DE- Sign of the Declination (J2000) 25- 26 I2 deg DEd Degree of Declination (J2000) 28- 29 I2 arcmin DEm Arcminute of Declination (J2000) 31- 36 F6.3 arcsec DEs Arcsecond of Declination (J2000) 38- 42 F5.2 mag r'mag ? Total magnitude in r'-band 44- 48 F5.2 mag i'mag ? Total magnitude in i'-band 50- 53 F4.2 mag r'-i ? Sloan r'-i color measured inside a fixed aperture of 1.2" 55- 62 F8.6 --- z Redshift, corrected to the heliocentric system 64- 71 F8.6 --- e_z Uncertainty in z 73- 77 F5.2 --- R ? R value (Tonry & Davis 1979AJ.....84.1511T) 79 I1 --- NEm [2/8]? Number of emission lines used to calculate the redshift 81- 87 A7 --- Memb Membership flag (3)
Note (1): Group as follows: A = Galaxy within 0.5 r200 of the X-ray centroid of the Cheshire Cat; B = Galaxy within 0.5-1.0 r200 of the X-ray centroid of the Cheshire Cat; C = Galaxy within 1.0-1.5 r200 of the X-ray centroid of the Cheshire Cat. Where r200 approximates the virial radius where the average mass density inside this radius is 200 times the critical density of the universe. Note (2): With B1-B23 from Bayliss et al. (2014ApJ...783...41B). Note (3): Flag as follows: Y/G1 = Member galaxy of G1, the eastern eye group; Y/G1(E) = The G1 central galaxy; Y/G2 = Member galaxy of G2, the western eye group; Y/G2(W) = The G2 central galaxy; N = Background/foreground galaxy.
History: From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 19-Sep-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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