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| '''R. M. Rich: Mapping of the bulge extended horizontal branch; does the bulge contain massive He burning stars?''' | ||[[Team Members]]|| ||[[Projects]]|| ||[[Data products]]|| ||[[Publications]]|| ||[[Conference contributions, colloquia, etc.]]|| ||[[Acknowledgments]]|| |
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| ''Collaboration:'' open to BDBS team members; current interest from Johnson, Clarkson, and de Propris | Add a logo. |
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| ''Abstract:'' We propose to map the morphology and extent of the blue horizontal branch in the Galactic bulge, using the globular clusters such as NGC 6522 (that has an EHB) in the BDBS footprint as templates. We seek to determine whether the morphology of the EHB depends on Galactic latitude or longitude, and we propose to match with Gaia and Galex archival data when possible. Saha et al. (2018) argue that a young, massive stellar population of He burning stars may be widespread int he bulge and we propose to use the BDBS u-band photometry to help set limits on such a population. |
The Blanco DECam Bulge Survey (BDBS) is an LSST precursor program to image ~200 sq. deg. of the Galactic bulge from -10 < l < +10 to -10 < b <-2.<<BR>> BDBS targets the relatively low extinction regions of the Southern Galactic bulge. The Survey is in ugrizY, obtained with DECam,<<BR>> with the goal of retaining precise photometric calibration even at the bright end. |
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| These pages contain an overview of all of the team's activities. | |
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| ---- '''R. de Propris: N-rich stars and multiple populations''' ''Abstract:'' My proposal, to elaborate on the one below, is to search for the presence of N-rich stars that are the hallmark of stars with MP2 abundances (in the parlance of Bastian & Lardo 2018), i.e., they are enriched in helium. We have shown that this is likely the cause of the UV excess in ETGs and that this is likely something that occurs in all stellar populations with ETG-like star-formation histories. Several authors have shown that the presence of these stars leads to a split or broadening of the red giant branch through the influence of N on the NH and CN lines (the effect is even stronger for main sequence stars). My proposal is to compare the scatter on the principal sequences in u-g vs all other colours, accounting for differential reddening and for the photometric errors. Through mixture modelling we can then estimate whether these stars exist in the Galactic Bulge and their importance, and possibly explore the radial dependence (i.e., if they are centrally concentrated, as the UV upturn sources appear to be in ETGs). ---- '''Will Clarkson: Accurate photometry from bleeding stars in wide-field imagers''' ''Collaboration:'' open to all who want to help; development so far has been performed by Clarkson, with testing by UM-Dearborn undergraduates and with some input from Kathy Vivas. ''Abstract:'' All imaging observations in the Galactic plane are sensitive to charge bleeding from interlopers, in which a relatively small number of luminous and/or nearby objects are so saturated in typical (~1 minute) main-program exposures that they bleed across much of the detector. Summation along the bleed provides a promising method to recover the flux for bright objects from long exposures, although the application of this technique to crowded fields is not entirely trivial. With "long" (~1 minute), "short" (~5s) and "very short" (~0.5s) exposures in all filters, BDBS provides a beautiful dataset to develop the techniques of summing along the bleed in crowded regions, with typically thousands of strongly-bled objects across the focal plane in typical regions. The scientific payoff includes a much larger set of useful exposures for bright objects (such as RR Lyrae) in program observations. We have performed initial investigations into charge bleeding in BDBS data, producing a tool that isolates charge-bleed objects in long exposures, constructs shaped apertures (for both the object and sky), performs simple photometry, and compares the result to expectations from short exposures of the same field. This has been developed using a single, particularly crowded image in one field. Now we wish to (i) test at all filters and across a much wider range of crowding levels; (ii) complete the implementation of neighbor-subtraction photometry (in which scaled neighbor objects are subtracted from under the bleed), (iii) complete the testing of the methods, and (iv) write the results up. Stretch-goals include the construction of an "effective PSF" for strongly saturated objects (although it is not obvious at this stage if the fine structure of a charge-bled PSF is strictly reproducible - it would be good to test this). Data required: Due to its focus on the pixel-data, this project mainly requires the imaging data, which we have been downloading from the NOAO archive as needed. However, the BDBS v2 catalog would be very useful as a truth-table to short-circuit certain parts of the testing. |
'''Please refer to the following Data Access Plan for the detailed survey policies:''' [[attachment:BDBS_Agreement.pdf]] The data are found on the [[https://bdbs.sca.iu.edu/index/front|server hosted by Indiana University]]. |
Add a logo.
The Blanco DECam Bulge Survey (BDBS) is an LSST precursor program to image ~200 sq. deg. of the Galactic bulge from -10 < l < +10 to -10 < b <-2.
BDBS targets the relatively low extinction regions of the Southern Galactic bulge. The Survey is in ugrizY, obtained with DECam,
with the goal of retaining precise photometric calibration even at the bright end.
These pages contain an overview of all of the team's activities.
Please refer to the following Data Access Plan for the detailed survey policies: BDBS_Agreement.pdf
The data are found on the server hosted by Indiana University.