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J/AJ/114/2381       UBVI photometry of NGC 7252              (Miller+, 1997)

The star cluster system of the merger remnant NGC 7252. Miller B.W., Whitmore B.C., Schweizer F., Fall S.M. <Astron. J. 114, 2381 (1997)> =1997AJ....114.2381M
ADC_Keywords: Galaxies, photometry ; Photometry, UBVRI ; Clusters, globular Abstract: We present new U, B, V, and I images of the prototypical merger remnant NGC 7252 obtained with the WFPC2 instrument of the Hubble Space Telescope. The photometry reaches about 3 mag deeper than the previous observations with WF/PCI and we detect 499 cluster candidates, most of them previously undiscovered. We can distinguish three populations of star clusters. We confirm the existence of a very luminous, blue population of clusters with a narrow range in color. Comparisons with Bruzual & Charlot (1996, in preparation) models incorporating a Salpeter stellar IMF show that the mean ages of these clusters are 650Myr for [Fe/H]=0.0 and 750 Myr if [Fe/H]=-0.3. Therefore, these are the clusters that formed during the merger event. The upper limit to the effective radii of these objects is 4.8±0.4pc (for D=64.4Mpc, H0=75), suggesting that they have physical properties like Galactic globular clusters. The second population of clusters is associated with the inner disk. Their (U-B) colors and reddening-free Q values indicate that their light is dominated by O stars and that they have ages less than 10Myr. However, with <Reff≥8.3±0.6pc, these objects may be more like stellar associations and they may not survive for a significant time. Finally, there is also evidence for the presence of the most luminous of the old, metal-poor globular clusters that belonged to the progenitor galaxies. The cluster luminosity function is a single power law with slope α~-1.8 down to a limiting magnitude of V=26. The current specific cluster frequency is SN=0.6±0.3 for old clusters and young clusters with M>105M, but after the remnant has faded for about 15Gyr SN will have increased to about 2.5. The central disk is now resolved into much finer detail than in earlier WF/PCI observations and the light profile of the nuclear region is consistent with a single power law with slope γ=-1.26±0.03. After both the main body and the cluster system of NGC 7252 have aged, for several Gyr it may have the properties of a field elliptical. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file tables.dat 84 80 Cluster candidates in NGC 7252
Byte-by-byte Description of file: tables.dat
Bytes Format Units Label Explanations
1- 2 I2 --- MWS97 Sequential number ([MWS97] NN in simbad) 4- 10 F7.3 arcsec oRA Offset from right ascension (1) 12- 18 F7.3 arcsec oDE Offset from declination (1) 20- 24 F5.2 arcsec rproj Projected radius 26- 30 F5.2 mag Vmag V magnitude corrected for foreground extinction 32- 35 F4.2 mag e_Vmag rms uncertainty on Cmag 37- 41 F5.2 mag U-B ? U-B colour index corrected for foreground extinction 43- 46 F4.2 mag e_U-B ? rms uncertainty on U-B 48- 52 F5.2 mag B-V ? B-V colour index corrected for foreground extinction 54- 57 F4.2 mag e_B-V ? rms uncertainty on B-V 59- 63 F5.2 mag V-I ? V-I colour index corrected for foreground extinction 65- 68 F4.2 mag e_V-I ? rms uncertainty on V-I 70- 74 F5.2 mag Q ? Reddening-free index Q=(U-B)-0.72(B-V) 76- 79 F4.2 mag e_Q ? rms uncertainty on Q 81- 84 F4.1 pc Reff ? Effective radius
Note (1): Coordinates are with respect to the nuclear position: RA=22:20:44.775, DE=-24:40:41.831, J2000. A positive offset indicates that the object is east or north of the nucleus.
History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 22-Mar-1999
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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