Investigation of open clusters based on IPHAS and APASS survey data

Abstract

We adapt the classical Q-method based on a reddening-free parameter constructed from three passband magnitudes to the filter set of IPHAS survey and combine it with the maximum-likelihood-based cluster parameter estimator by Naylor & Jeffries (2006) to determine the extinction, heliocentric distances, and ages of young open clusters using H α ri data. The method is also adapted for the case of significant variations of extinction across the cluster field. Our technique is validated by comparing the colour excesses, distances, and ages determined in this study with the most bona fide values reported for the 18 well-studied young open clusters in the past and a fairly good agreement is found between our extinction and distance estimates and earlier published results, although our age estimates are not very consistent with those published by other authors. We also show that individual extinction values can be determined rather accurately for stars with (r − i) > 0.1. Our results open up a prospect for determining a uniform set of parameters for northern clusters based on homogeneous photometric data, and for searching for new, hitherto undiscovered open clusters.

Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue

“…The distances to OB stars inferred from interstellar calcium lines, whose mean error is estimated to be 15%, proved to be good (Megier et al 2005(Megier et al , 2009; Galazutdinov et al 2015). Important results were obtained by various authors using the group distances to OB stars when analyzing young OB associations and OSCs, whose mean error is estimated to be 15-20% (Blaha and Humphreys 1989;Zabolotskikh et al 2002; Mel'nik and Dambis 2009. Reliable trigonometric parallax estimates for OB stars have been obtained only recently.…”

A Comprehensive Study of 94 Open Clusters Based on the Data from IPHAS, GAIA DR2, and Other Sky Surveys

“…This survey, which was carried out on the 2.5m Isaac Newton Telescope (INT) in the northern part of the sky, covers the Galactic longitudes l= 30 o -215 o and latitudes |b|¡ 5 o down to a limiting magnitude of 21.2 mag, 20.0 mag, and 20.3 mag in the r, i, and H α filters, respectively. Dambis et al [4] modified the classical Q-method of Johnson and Morgan [10] and applied it to r-, i-, and H α -band magnitudes to construct the reddening-free index H α index = (0.755r + 0.245i -H α ). Like in the paper of Dambis et al [4], here we use the (H α index, r-i) diagram to determine the color excess E(r − i).…”

“…Dambis et al [4] modified the classical Q-method of Johnson and Morgan [10] and applied it to r-, i-, and H α -band magnitudes to construct the reddening-free index H α index = (0.755r + 0.245i -H α ). Like in the paper of Dambis et al [4], here we use the (H α index, r-i) diagram to determine the color excess E(r − i). The reddening lines in this diagram are parallel to the horizontal axis because the combination (0.755r + 0.245i) linearly interpolates between the corresponding photometric passbands and sort of imitates a broadband H α filter so that H α index does not depend on reddening.…”

Search for and Investigation of Double Open Clusters

“…We determined the physical parameters of the open cluster NGC 1857 using the new method developed by Dambis et al (2017). We first determined the E r−i color excess from the IPHAS catalog data.…”