High-resolution Extinction Map in the Direction of the Bulge Globular Cluster NGC 6440^*

Abstract

We used optical images acquired with the UVIS channel of the Wide Field Camera 3 on board of the Hubble Space Telescope to construct the first high-resolution extinction map in the direction of NGC 6440, a globular cluster located in the bulge of our Galaxy. The map has a spatial resolution of 0.5 over a rectangular region of about 160 × 240 around the cluster center, with the long side in the North-West/South-East direction. We found that the absorption clouds show patchy and filamentary sub-structures with extinction variations as large as δE(B − V ) ∼ 0.5 mag. We also performed a first-order proper motion analysis to distinguish cluster members from field interlopers. After the field decontamination and the differential reddening correction, the cluster sequences in the colormagnitude diagram appear much better defined, providing the best optical color-magnitude diagram so far available for this cluster.

Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data

“…Typical uncertainties in the zero points of the P/L relations of RR Lyrae stars are thought to be of order 0.05 mag (Bhardwaj 2020) and other methods like CMD fitting have similar uncertainties. In addition, the reddening of many clusters presents an additional challenge for the determination of accurate distances since it can be variable even across small, arcminute size fields Pallanca et al 2019). Furthermore there is evidence for non-standard reddening laws in the directions of several globular clusters like for example M4 (Dixon & Longmore 1993;Hendricks et al 2012).…”

Digging for Relics of the Past: The Ancient and Obscured Bulge Globular Cluster NGC 6256

“…A deep investigation of these systems is thus crucial to constrain the slope of the presumed age-[Fe/H] relation, which is still completely unknown, but could bring precious information on the bulge formation processes. This work is part of an ongoing large program aimed at characterizing the stellar populations of highly extincted stellar systems orbiting within the Galactic bulge, which led us to the discovery of the surprising properties of the stellar system Terzan 5 (see Ferraro et al 2009Ferraro et al , 2015Ferraro et al , 2016Lanzoni et al 2010;Origlia et al 2011Origlia et al , 2013Origlia et al , 2019Massari et al 2012Massari et al , 2014aCadelano et al 2018) and other intriguing clusters (Saracino et al 2015(Saracino et al , 2016(Saracino et al , 2019Pallanca et al 2019). This paper focused on NGC 6256.…”

“…Indeed, such a systematic error is smaller than the photometric errors and significantly smaller than the typical uncertainties on the differential reddening corrections that we are going to derive. See, e.g.,Pallanca et al (2019).…”

The RGB tip of galactic globular clusters and the revision of the axion-electron coupling bound

“…To perform the cross-correlation, we used CataXcorr, a code aimed at cross-correlating catalogs and finding astrometric solutions, developed by P. Montegriffo at INAF -OAS Bologna. This package has been successfully used in a large number of papers in the past years, in particular,Pallanca et al (2013Pallanca et al ( , 2014Pallanca et al ( , 2019,Cadelano et al (2017), andDalessandro et al (2014). A166, page 7 of 14A&A 644, A166 (2020) …”