Hot Horizontal‐Branch Stars in the Galactic Bulge. I.

Peterson, R. C.; Terndrup, D. M.; Sadler, E. M.; Walker, A. R.

doi:10.1086/318334

Cited by 10 publications

(13 citation statements)

References 58 publications

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“…In the Galactic bulge, evidence of the presence of hot HB stars has been provided and discussed by Bertelli et al (1996), Terndrup et al (1999Terndrup et al ( , 2004, Peterson et al (2001), Busso et al (2005), and Busso and Moehler (2008). It should also be noted that the precise RGB mass loss recipe adopted may also significantly impact the predicted production of UV sources (see Sect.…”

Section: The M V (Rrl) − [Fe/h] Relation: Linear Quadraticmentioning

confidence: 97%

Horizontal branch stars: the interplay between observations and theory, and insights into the formation of the Galaxy

Catelan

2009

Astrophys Space Sci

358

430

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We review and discuss horizontal branch (HB) stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC-an argument which, due to its strong reliance on the ancient RR Lyrae stars, is essentially independent of the chemical evolution of these systems after the very earliest epochs in the Galaxy's history. Convenient analytical fits to isochrones in the HB type-[Fe/H] plane are also provided. In this sense, a rediscussion of the second-parameter problem is also presented, focusing on the cases of NGC 288/NGC 362, M13/M3, the extreme outer-halo globular clusters with predominantly red HBs, and the metal-rich globular clusters NGC 6388 and NGC 6441. The recently revived possibility that the helium abundance may play an important role as a second parameter is also addressed, and possible constraints on this scenario discussed. We critically discuss the possibility that the observed properties of HB stars in NGC 6388 and NGC 6441 might be accounted for if these clusters possess a relatively minor population of helium-enriched stars. A technique is M. Catelan is John Simon Guggenheim Memorial Foundation Fellow.M. Catelan ( ) proposed to estimate the HB types of extragalactic globular clusters on the basis of integrated far-UV photometry. The importance of bright type II Cepheids as tracers of faint blue HB stars in distant systems is also emphasized. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyr, is also revisited. Taking into due account the evolutionary status of RR Lyr, the derived relation implies a true distance modulus to the LMC of (m-M) 0 = 18.44 ± 0.11. Techniques providing discrepant slopes and zero points for the M V (RRL)-[Fe/H] relation are briefly discussed. We provide a convenient analytical fit to theoretical model predictions for the period change rates of RR Lyrae stars in globular clusters, and compare the model results with the available data. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are also investigated.

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Section: The M V (Rrl) − [Fe/h] Relation: Linear Quadraticmentioning

confidence: 97%

Horizontal branch stars: the interplay between observations and theory, and insights into the formation of the Galaxy

Catelan

2009

Astrophys Space Sci

358

430

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“…They are old objects, usually used to trace old, metal-poor structures such as the Galactic halo (Catelan 2009;Vickers et al 2012). In the Galactic bulge, although metal-rich BHB stars exist, the vast majority of them seem to be metal-poor (Peterson et al 2001;Terndrup et al 2004). Identifying old metal-poor stars in the fields of the Galactic bulge is difficult, as they make up a small fraction compared to the metal-rich component.…”

Section: Cmds Of the Galactic Bulge Fields In The Vvvmentioning

confidence: 99%

Milky Way demographics with the VVV survey

Alonso-García

Saito

Hempel

et al. 2018

A&A

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Context. The inner regions of the Galaxy are severely affected by extinction, which limits our capability to study the stellar populations present there. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey has observed this zone at near-infrared wavelengths where reddening is highly diminished. Aims. By exploiting the high resolution and wide field-of-view of the VVV images we aim to produce a deep, homogeneous, and highly complete database of sources that cover the innermost regions of our Galaxy. Methods. To better deal with the high crowding in the surveyed areas, we have used point spread function (PSF)-fitting techniques to obtain a new photometry of the VVV images, in the ZY JHKs near-infrared filters available. Results. Our final catalogs contain close to one billion sources, with precise photometry in up to five near-infrared filters, and they are already being used to provide an unprecedented view of the inner Galactic stellar populations. We make these catalogs publicly available to the community. Our catalogs allow us to build the VVV giga-CMD, a series of color-magnitude diagrams of the inner regions of the Milky Way presented as supplementary videos. We provide a qualitative analysis of some representative CMDs of the inner regions of the Galaxy, and briefly mention some of the studies we have developed with this new dataset so far.

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“…The most important remaining observational goal is to see whether the faint, blue stars we find on the MOSAIC CMDs are bulge EHB stars. We know from our 2dF spectra that the majority of the BHB stars bluer than the foreground disk and with B ≤ 18 are probably in the bulge, though there are also likely to be halo HB stars at larger distances and the occasional foreground A-type main-sequence star as found by Peterson et al (2001). We do not currently have spectra for the faintest candidates on Figure 3 to confirm their status as EHB stars in the bulge.…”

Section: Some Results and Future Plansmentioning

confidence: 72%

A Survey for EHB Stars in the Galactic Bulge

Terndrup

Hansen

et al. 2004

Astrophysics and Space Science

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We present a progress report on an extensive survey to find and characterize all types of blue horizontal-branch stars in the nuclear bulge of the Galaxy. We have obtained wide, shallow imaging in UBV of ~12 square degrees in the bulge, with follow-up spectroscopy for radial velocities and metal abundance determinations. We have discovered a number of metal-rich blue HB stars, whose presence in the bulge is expected by the interpretation of the extragalactic ultraviolet excess. Very deep images have been obtained in UBV and SDSS u along the bulge minor axis, which reveal a significant number of EHB candidates fainter than B = 19, i.e., with the same absolute magnitudes as EHB stars in several globular clusters.Comment: To appear in "Extreme Horizontal Branch Stars and Related Objects", Astrophysics and Space Science, Kluwer Academic Publishers, proceedings of the meeting held in Keele, UK, June 16-20, 200

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Hot Horizontal‐Branch Stars in the Galactic Bulge. I.

Cited by 10 publications

References 58 publications

Horizontal branch stars: the interplay between observations and theory, and insights into the formation of the Galaxy

Horizontal branch stars: the interplay between observations and theory, and insights into the formation of the Galaxy

Milky Way demographics with the VVV survey

A Survey for EHB Stars in the Galactic Bulge

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