ON THE ΔVbumpHBPARAMETER IN GLOBULAR CLUSTERS

Cecco, A. Di; Bono, G.; Stetson, P. B.; Pietrinferni, A.; Becucci, Rosa; Cassisi, S.; Degl’Innocenti, S.; Iannicola, G.; Moroni, P. G. Prada; Buonanno, R.; Calamida, A.; Caputo, F.; Castellani, M.; Corsi, C. E.; Ferraro, I.; Dall’Ora, M.; Monelli, M.; Nonino, M.; Piersimoni, A. M.; Pulone, L.; Romaniello, M.; Salaris, Maurizio; Walker, A. R.; Zoccali, M.

doi:10.1088/0004-637x/712/1/527

Cited by 52 publications

(87 citation statements)

References 52 publications

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“…In the models for the metal-rich cluster, M4, the onset of FDU is consistent with the observations whilst a discrepancy is present at the LF bump (≈ 0.4 mag). It is well documented that theoretical models underestimate the magnitude of the LF bump (Fusi Pecci et al 1990;Bjork & Chaboyer 2006;Di Cecco et al 2010;Cassisi et al 2011), however this is the first time a disagreement at FDU has been identified. The recent availability of lithium observations, which probe both RGB mixing events, allows for an investigation of FDU across a range of metallicities.…”

Section: Comparison With Models: Elucidating the Red Giant Branch MIXmentioning

confidence: 79%

“…(i) By comparing the parameter ∆V bump HB = V bump − VHB; the V magnitude difference between the RGB bump and the horizontal branch at the RR Lyrae instability strip magnitude (Fusi Pecci et al 1990;Zoccali et al 1999;Salaris, Cassisi & Weiss 2002;Riello et al 2003;Bjork & Chaboyer 2006;Meissner & Weiss 2006;Di Cecco et al 2010). …”

Section: Analysis Of the Photometric Datamentioning

confidence: 99%

“…In their analysis of the ∆V bump HB parameter, Riello et al (2003) find good agreement between theory and observations at higher metallicities but note significant discrepancies at low metallicity. Investigations of low-metallicity GCs include those by Fusi Pecci et al (1990) and Di Cecco et al (2010), who also used the parameter ∆V bump HB , to determine that at [M/H] −1.7, models underestimate the magnitude of the LF bump by at least 0.4 mag. Di Cecco et al (2010) also conducted tests on the effects of the microphysics and determined that models with α-element and CNO-enhancements could not account for the discrepancy nor could the revised solar heavy-element mixture.…”

Section: Analysis Of the Photometric Datamentioning

confidence: 99%

“…Investigations of low-metallicity GCs include those by Fusi Pecci et al (1990) and Di Cecco et al (2010), who also used the parameter ∆V bump HB , to determine that at [M/H] −1.7, models underestimate the magnitude of the LF bump by at least 0.4 mag. Di Cecco et al (2010) also conducted tests on the effects of the microphysics and determined that models with α-element and CNO-enhancements could not account for the discrepancy nor could the revised solar heavy-element mixture. Cassisi et al (2011), who employed the ∆V MSTO bump parameter, found that the theoretical bump was too bright by 0.2 magnitudes on average, but discrepancies of ∆MV 0.4 magnitudes in the lowestmetallicity clusters were within the uncertainties.…”

Section: Analysis Of the Photometric Datamentioning

confidence: 99%

“…The chosen metallicity scale is also a source of uncertainty and has been discussed in previous studies (Riello et al 2003;Di Cecco et al 2010;Cassisi et al 2011). Di Cecco et al (2010), in particular, find that by adopting two different sets of independently determined metallicites for their GC sample, their conclusions remain unchanged.…”

Section: The Distance Modulus and Metallicity Scalementioning

confidence: 99%

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Diagnostics of stellar modelling from spectroscopy and photometry of globular clusters

Angelou

D’Orazi

Constantino

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We conduct a series of comparisons between spectroscopic and photometric observations of globular clusters and stellar models to examine their predictive power. Data from medium-to-high resolution spectroscopic surveys of lithium allow us to investigate first dredge-up and extra mixing in two clusters well separated in metallicity. Abundances at first dredge-up are satisfactorily reproduced but there is preliminary evidence to suggest that the models overestimate the luminosity at which the surface composition first changes in the lowest-metallicity system. Our models also begin extra mixing at luminosities that are too high, demonstrating a significant discrepancy with observations at low metallicity. We model the abundance changes during extra mixing as a thermohaline process and determine that the usual diffusive form of this mechanism cannot simultaneously reproduce both the carbon and lithium observations. Hubble Space Telescope photometry provides turnoff and bump magnitudes in a large number of globular clusters and offers the opportunity to better test stellar modelling as function of metallicity. We directly compare the predicted main-sequence turn-off and bump magnitudes as well as the distance-independent parameter ∆M V MSTO bump . We require 15 Gyr isochrones to match the main-sequence turn-off magnitude in some clusters and cannot match the bump in low-metallicity systems. Changes to the distance modulus, metallicity scale and bolometric corrections may impact on the direct comparisons but ∆M V MSTO bump , which is also underestimated from the models, can only be improved through changes to the input physics. Overshooting at the base of the convective envelope with an efficiency that is metallicity dependent is required to reproduce the empirically determined value of ∆M V MSTO bump .

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Section: Comparison With Models: Elucidating the Red Giant Branch MIXmentioning

confidence: 79%