The open cluster IC 1805 and its vicinity: investigation of stars in the Vilnius, IPHAS, 2MASS, and WISE systems

Abstract

The results of CCD photometry in the Vilnius seven-color system down to V = 18 mag are presented for 242 stars in the direction of the young open cluster IC 1805 that is located in the active star-forming region W4 in the Cas OB6 association. Photometric data were used to classify stars into spectral and luminosity classes, and to determine their interstellar reddenings, extinctions and distances. We confirm the CH 3 OH and H 2 O maser VLBA parallax results that the cluster is located close to the front side of the Perseus arm, at a distance about 2.0 kpc. In the color-magnitude diagram, zero-age main sequence (ZAMS) stars of the cluster extend to spectral class A0. The extinction values for the majority of the cluster stars are between 2.2 and 2.7 mag, with a mean value of 2.46 mag. This extinction originates mainly between the Sun and the outer edge of the Local arm, in accordance with the distribution of CO clouds. In the Perseus arm and beyond, the extinction was investigated using the classification and reddening determination for A0-F0 stars measured in the r, i, Hα system of the IPHAS survey to r = 19 mag. The extinction A V within the Perseus arm ranges from 2.5-4.5 mag at the front edge to 3.0-5.0 mag at the far edge. Possibly, we have found about 20 early A-type stars located in the Outer arm. The 2MASS JHK s photometry for red giants gives much higher extinction values (up to about 6 mag), which would correspond to the stars located behind dense clouds of both arms. In the area, using the WISE, 2MASS, and IPHAS photometry data, 18 possible young stellar objects (YSOs) of low masses are identified. Six high-mass YSOs (five Ae/Be stars and a F6e star) are known from previous investigations.

X-ray and optical spectroscopy of the massive young open cluster IC 1805

“…In Simbad, it appears close to 2MASS J02324314+6130587 (which has a likely YSO classification in Broos et al 2013, and a class II YSO classification in Sung et al, in prep.). Straižys et al (2013) reported a WISE counterpart, suggesting this object to be an Ae/Be highmass YSO (see also Sect. 4.2).…”

“…The optical/IR counterpart is a likely YSO ) lying in the PMS locus (Sung et al, in prep.). Straižys et al (2013) quoted a photometric spectral type G for this object.…”

“…The former Chandra source is a likely YSO ), more precisely classified as a class II YSO by Sung et al (in prep. ); it is also known as 2MASS J02320924+6130404 and was found to be a WISE source probably associated with a YSO (Straižys et al 2013). Compared to Chandra observations (see photon flux and median energy in Townsley et al 2014), its X-ray flux has quadrupled.…”

The dark cloud TGU H994 P1 (LDN 1399, LDN 1400, and LDN 1402): Interstellar extinction and distance

“…For about 73% of stars, two-dimensional spectral types (spectral and luminosity classes) were determined applying two classification codes based on interstellar reddening-free Q-parameters. One of these codes, COMPAR, applies a comparison of Q-parameters of stars in the area and individual standard stars (Straižys et al 2013). The second code, now renamed to KLASQ, is described in Milašius et al (2013).…”

Massive Stars in the SDSS-IV/APOGEE-2 Survey. II. OB-stars in the W345 Complexes

“…Bik et al (2012) suggest that W3-Main harbors several H II regions, ranging from very young hyper-compact H II regions (HCHfew 10 3 yr old) and ultra-compact H II regions (UCH-about 10 5 yr old) to more evolved, diffuse H II regions with ages of a few 10 6 yr (Wood & Churchwell 1989). The massive stars in IC 1805 have been characterized (e.g., Rauw & De Becker 2004;De Becker et al 2006;Rauw & Nazé 2016), along with multi-wavelength studies of the low and intermediate-mass population (e.g., Straižys et al 2013;Panwar et al 2017) and of the physics of the W4 super-bubble expansion (e.g., Basu et al 1999;Gao et al 2015). For the W5 complex, studies like those of Karr & Martin (2003) and Niwa et al (2009) discuss the expansion of the H II regions and the effects on cluster evolution.…”