2003A&A...410..553R

Query : 2003A&A...410..553R

2003A&A...410..553R - Astronomy and Astrophysics, volume 410, 553-563 (2003/11-1)

The Red Giant Branch luminosity function bump.

RIELLO M., CASSISI S., PIOTTO G., RECIO-BLANCO A., DE ANGELI F., SALARIS M., PIETRINFERNI A., BONO G. and ZOCCALI M.

Abstract (from CDS):

We present observational estimates of the magnitude difference between the luminosity function red giant branch bump and the horizontal branch (ΔF555WbumpHB), and of star counts in the bump region (Rbump), for a sample of 54 Galactic globular clusters observed by the HST. The large sample of stars resolved in each cluster, and the high photometric accuracy of the data allowed us to detect the bump also in a number of metal poor clusters. To reduce the photometric uncertainties, empirical values are compared with theoretical predictions obtained from a set of updated canonical stellar evolution models which have been transformed directly into the HST flight system. We found an overall qualitative agreement between theory and observations. Quantitative estimates of the confidence level are hampered by current uncertainties on the globular cluster metallicity scale, and by the strong dependence of ΔF555WbumpHB on the cluster metallicity. In case of the Rbump parameter, which is only weakly affected by the metallicity, we find a very good quantitative agreement between theoretical canonical models and observations. For our full cluster sample the average difference between predicted and observed Rbump values is practically negligible, and ranges from -0.002 to -0.028, depending on the employed metallicity scale. The observed dispersion around these values is entirely consistent with the observational errors on Rbump. As a comparison, the value of Rbump predicted by theory in case of spurious bump detections due to Poisson noise in the stellar counts would be ∼0.10 smaller than the observed ones. We have also tested the influence on the predicted ΔF555WbumpHB and Rbump values of an He-enriched component in the cluster stellar population, as recently suggested by D'Antona et al. (2002A&A...395...69D). We find that, under reasonable assumptions concerning the size of this He-enriched population and the degree of enrichment, the predicted ΔF555WbumpHB and Rbump values are only marginally affected.

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Journal keyword(s): Galaxy: globular clusters: general - stars: luminosity function, mass function - stars: evolution - stars: statistics

Simbad objects: 54

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Number of rows : 54
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 3914 0
2 NGC 362 GlC 01 03 14.26 -70 50 55.6     6.58     ~ 1084 0
3 NGC 1261 GlC 03 12 16.21 -55 12 58.4     8.63     ~ 520 0
4 NGC 1851 GlC 05 14 06.76 -40 02 47.6           ~ 1429 0
5 M 79 GlC 05 24 10.59 -24 31 27.3     8.16     ~ 816 0
6 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1419 0
7 M 68 GlC 12 39 27.98 -26 44 38.6     7.96     ~ 997 0
8 NGC 4833 GlC 12 59 33.92 -70 52 35.4           ~ 425 0
9 M 53 GlC 13 12 55.25 +18 10 05.4     7.79     ~ 836 0
10 NGC 5634 GlC 14 29 37.28 -05 58 35.1   10.69 10.05     ~ 300 0
11 NGC 5694 GlC 14 39 36.52 -26 32 18.0           ~ 301 0
12 IC 4499 GlC 15 00 18.57 -82 12 49.6     8.56     ~ 351 0
13 NGC 5824 GlC 15 03 58.612 -33 04 06.70   10.28 9.56     ~ 408 0
14 M 5 GlC 15 18 33.22 +02 04 51.7     5.95     ~ 1977 0
15 NGC 5927 GlC 15 28 00.69 -50 40 22.9           ~ 462 0
16 NGC 5946 GlC 15 35 28.58 -50 39 35.0           ~ 194 0
17 NGC 5986 GlC 15 46 03.00 -37 47 11.1     6.92     ~ 374 0
18 M 80 GlC 16 17 02.41 -22 58 33.9           ~ 715 0
19 NGC 6139 GlC 16 27 39.987 -38 50 57.03   11.03 9.68     ~ 214 0
20 M 107 GlC 16 32 31.86 -13 03 13.6           ~ 786 0
21 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2191 0
22 NGC 6229 GlC 16 46 58.641 +47 31 36.38   9.38 9.86     ~ 366 0
23 M 12 GlC 16 47 14.18 -01 56 54.7     6.07     ~ 676 0
24 NGC 6235 GlC 16 53 25.36 -22 10 38.8   11.99 7.20     ~ 186 0
25 M 62 GlC 17 01 12.60 -30 06 44.5           ~ 619 0
26 NGC 6284 GlC 17 04 28.747 -24 45 51.22   10.72 7.43     ~ 278 0
27 NGC 6293 GlC 17 10 10.42 -26 34 54.2           ~ 281 0
28 NGC 6342 GlC 17 21 10.14 -19 35 14.7     10.01     ~ 286 0
29 NGC 6356 GlC 17 23 34.99 -17 48 46.9   10.01 7.42     ~ 350 1
30 NGC 6355 GlC 17 23 58.65 -26 21 12.3   12.46 11.05     ~ 155 0
31 NGC 6362 GlC 17 31 54.99 -67 02 54.0           ~ 585 0
32 NGC 6388 GlC 17 36 17.461 -44 44 08.34           ~ 913 1
33 M 14 GlC 17 37 36.15 -03 14 45.3   9.55 5.73     ~ 385 0
34 NGC 6441 GlC 17 50 13.06 -37 03 05.2           ~ 884 0
35 NGC 6453 GlC 17 50 51.77 -34 35 55.1   10.49       ~ 166 0
36 NGC 6522 GlC 18 03 34.08 -30 02 02.3           ~ 524 0
37 NGC 6544 GlC 18 07 20.58 -24 59 50.4   11.36 9.90     ~ 296 0
38 NGC 6569 GlC 18 13 38.88 -31 49 35.2   10.78 9.47     ~ 238 0
39 NGC 6584 GlC 18 18 37.60 -52 12 56.8     8.17     ~ 288 0
40 NGC 6624 GlC 18 23 40.51 -30 21 39.7           ~ 885 1
41 NGC 6638 GlC 18 30 56.25 -25 29 47.1   10.81 9.68     ~ 234 0
42 M 69 GlC 18 31 23.10 -32 20 53.1           ~ 462 0
43 NGC 6642 GlC 18 31 54.23 -23 28 34.1   11.30 10.24     ~ 206 0
44 NGC 6652 GlC 18 35 45.63 -32 59 26.6           ~ 437 0
45 M 70 GlC 18 43 12.76 -32 17 31.6           ~ 385 0
46 NGC 6717 GlC 18 55 06.04 -22 42 05.3           ~ 244 0
47 NGC 6723 GlC 18 59 33.15 -36 37 56.1           ~ 499 0
48 NGC 6760 GlC 19 11 12.06 +01 01 49.7   11.37 9.78     ~ 240 0
49 M 71 GlC 19 53 46.49 +18 46 45.1           ~ 1127 0
50 M 75 GlC 20 06 04.841 -21 55 20.14     8.26     ~ 366 0
51 NGC 6934 GlC 20 34 11.37 +07 24 16.1           ~ 422 0
52 M 72 GlC 20 53 27.70 -12 32 14.3     8.96     ~ 430 0
53 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3138 0
54 M 2 GlC 21 33 27.02 -00 49 23.7     6.25     ~ 1030 1

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