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J/A+A/611/A21       Globular cluster candidates in NGC253     (Cantiello+, 2018)

A VST and VISTA study of globular clusters in NGC253. Cantiello M., Grado A., Rejkuba M., Arnaboldi M., Capaccioli M., Greggio L., Iodice E., Limatola L. <Astron. Astrophys. 611, A21 (2018)> =2018A&A...611A..21C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry, ugriz ; Photometry, infrared Keywords: galaxies: star clusters: general - galaxies: individual: NGC253 - galaxies: stellar content - galaxies: evolution - catalogs - galaxies: photometry Abstract: Globular clusters (GCs) are key to our understanding of the Universe, as laboratories of stellar evolution, fossil tracers of the past formation epoch of the host galaxy, and effective distance indicators from local to cosmological scales. We analyze the properties of the sources in the NGC 253 with the aim of defining an up to date catalog of GC candidates in the galaxy. Given the distance of the galaxy, GCs in NGC 253 are ideal targets for resolved color-magnitude diagram studies of extragalactic GCs with next-generation diffraction limited ground-based telescopes. Our analysis is based on the science verification data of two ESO survey telescopes, VST and VISTA. Using ugri photometry from VST and JKs from VISTA, GC candidates were selected using as reference the morpho-photometric and color properties of spectroscopically confirmed GCs available in the literature. The strength of the results was verified against available archival HST/ACS data from the GHOSTS survey: all but two of the selected GC candidates appear as star clusters in HST footprints. The adopted GC selection leads to the definition of a sample of ∼350 GC candidates. At visual inspection, we find that 82 objects match all the requirements for selecting GC candidates and 155 are flagged as uncertain GC candidate; however, 110 are unlikely GCs, which are most likely background galaxies. Furthermore, our analysis shows that four of the previously spectroscopically confirmed GCs, i.e., ∼20% of the total spectroscopic sample, are more likely either background galaxies or high-velocity Milky Way stars. The radial density profile of the selected best candidates shows the typically observed r1/4-law radial profile. The analysis of the color distributions reveals only marginal evidence of the presence of color bimodality, which is normally observed in galaxies of similar luminosity. The GC luminosity function does not show the typical symmetry, mainly because of the lack of bright GCs. Part of the bright GCs missing might be at very large galactocentric distances or along the line of sight of the galaxy dusty disk. As an alternative possibility, we speculate that a fraction of low luminosity GC candidates might instead be metal-rich, intermediate age clusters, but fall in a similar color interval of old, metal-poor GCs. Defining a contaminant-free sample of GCs in extragalactic systems is not a straight forward exercise. Using optical and near-IR photometry we purged the list of GCs with spectroscopic membership and photometric GC candidates in NGC 253. Our results show that the use of either spectroscopic or photometric data only does not generally ensure a contaminant-free sample and a combination of both spectroscopy and photometry is preferred. Description: Photometric catalogs for globular cluster (GC) candidates over the 1 sq. degree area around NGC253. The catalogues are based on ugri-band photometry from the VST data, and JKs photometry from VISTA. Aperture magnitudes, corrected for aperture correction are reported. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 234 347 Globular cluster candidates in NGC253
See also: J/ApJ/602/231 : Chandra X-ray point sources in nearby galaxies (Colbert+, 2004) J/AJ/127/2674 : Globular clusters in Sculptor group (Olsen+, 2004) J/A+A/611/A93 : NGC3115 & NGC1399 VEGAS-SSS globular clusters (Cantiello+ 2018) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 I3 --- ID [1/347] Internal designation 5- 13 F9.6 deg RAdeg Right ascension (J2000.0) 15- 24 F10.6 deg DEdeg Declination (J2000.0) 26- 31 F6.3 mag umag VST u-band aperture magnitude (1) 33- 37 F5.3 mag e_umag VST u-band magnitude error 39- 44 F6.3 mag gmag ?=99.000 VST g-band aperture magnitude (1) 46- 50 F5.3 mag e_gmag ?=9.000 VST g-band magnitude error 52- 57 F6.3 mag rmag VST r-band aperture magnitude (1) 59- 63 F5.3 mag e_rmag VST r-band magnitude error 65- 70 F6.3 mag imag VST i-band aperture magnitude (1) 72- 76 F5.3 mag e_imag VST i-band magnitude error 78- 83 F6.3 mag Jmag ?=99.999 VISTA J-band aperture magnitude (1) 85- 89 F5.3 mag e_Jmag ?=9.000 VISTA J-band magnitude error 91- 96 F6.3 mag Ksmag ?=99.999 VISTA Ks-band aperture magnitude (1) 98-102 F5.3 mag e_Ksmag ?=9.000 VISTA Ks-band magnitude error 104 A1 --- l_Rh Limit flag on Rh 105-110 F6.3 pc Rh Half-light radius (2) 112-117 F6.4 pc e_Rh Error on Half-light radius 119-125 F7.4 --- b/a Axis ratio 127-168 A42 --- OtherID Other identification from the literature (3) 170-189 A20 --- Spectra Presence in GHOSTS footprints, spectroscopic or HST samples, or previous identifications in the photometric sample by Liller et al. (1983ApJ...265..166L) or Blecha (1986A&A...154..321B) (4) 190-224 A35 --- Visual Comments based on visual inspection (5) 226-234 A9 --- Class Final classification (Bona fide, Uncertain, No)
Note (1): Correction for foreground Galactic extinction according to Schlafly & Finkbeiner (2011ApJ...737..103S) recalibration of the Schlegel et al. (1998ApJ...500..525S) infrared-based dust map. Magnitudes are derived within 8 pixel aperture; aperture correction is applied. Note (2): The value of Rh is meaningless for sources classified as No in Class column. Note (3): Designations: LA83#NN GC candidate number NN ([LA83] NGC 253 NN in Simbad) in Liller et al. (1983ApJ...265..166L), cited as LANN in Beasley et al. (2000MNRAS.311..673B) B86#NN GC candidate number NN ([B86c] NN in Simbad) in Blecha (1986A&A...154..321B), cited as BNN in Beasley et al., (2000MNRAS.311..673B) BS00#NN GC candidate number NN ([BS2000] NGC 253 NN) in Beasley et al. (2000MNRAS.311..673B) OMS04#NN GC candidate number NN ([OMS2004] NGC 253 NNN in Simbad) in Olsen et al. (2004, Cat. J/AJ/127/2674) CHP04 source ([CHP2004] JHHMMSS.s+DDMMSS) in Simbad) in Colbert et al. (2004, Cat. J/ApJ/602/231) Redshift are from the Nasa Extragalactic Database. Note (4): Codes as follows: sgxy = spectroscopic confirmed galaxy sGC = spectroscopic confirmed GC GHOSTS#GC = star cluster candidate visible in GHOSTS footprints; galaxy in GHOSTS footprints BS00#tab.6 = photometric candidate GC from Beasley et al. (2000MNRAS.311..673B) OMS04weakspectrum = source with low signal to noise spectrum in Olsen et al. (2004, Cat. J/AJ/127/2674) HKW09 = An extended disk galaxy in a spiral galaxy discovered in the ACS Nearby Galaxy Survey Treasury observations of NGC253 (Holwerda et al., 2009AJ....137.3000H) N/A = Not analysed Note (5): Visual Inspection flags as follows: box10 = at least ∼10 sources equally bright or brighter observed in an area of 2'x2' features = faint extended structures close to or around the source NbriM = N similar or brighter sources within M arcseconds gxy-group? = the source is angularly close to several clearly extended or disk-shaped sources blend = close (<5") object, blended with the candidate J = indicates any of the previous flags, only observed in the J-band frame, the deepest in our dataset. elongated = elongated extended = extended faint = faint N/A = Not analysed
History: From Michele Cantiello, cantiello(at)oa-abruzzo.inaf.it Acknowledgements: INAF for financial support to the VSTceN
(End) Patricia Vannier [CDS] 06-Nov-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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