Poster abstract
The influence of massive stars on star formation in Cepheus OB2: Results from the IPHAS H-alpha survey
Abstract
The INT Photometric H-Alpha Survey (IPHAS) is a 1800 deg$^2$ survey of the Northern Galactic Plane, reaching down to r' $\sim$21 and nearing completion in 2010. We demonstrate how the survey can be used to (1) reliably select T-Tauri candidates and (2) constrain the accretion rates within 0.5 dex. IPHAS is a necessary addition to spectroscopic surveys because it allows large and uniform samples of accretion rates to be obtained with a precise handle on the selection effects.
We apply the method on a region of 7 deg$^2$ towards Cepheus OB2 and obtain 110 T-Tauri candidates with accretion rates greater than $10^{-9.5}~M_\odot$. Most of the bright candidates are confirmed by previous studies. In addition, we discover 50 new faint, low-mass candidates (r' $>$ 18.0; $M_* < 0.5~M_\odot$) which are densely clustered near the molecular clouds IC1396a and IC1396n. We show that these clouds are sites of ongoing star formation, driven by radiative implosion due to the massive star system HD206267A (O6.5V) at a distance of 5 to 15 pc. In contrast, within 2.5 pc from these hot stars we observe a decrease of accretion rates, which may be due to the destructive effects of UV-photoevaporation. Finally, we use our statistical sample to test recent claims on the steep dependency of accretion rates on stellar mass, and find that this dependency is largely due to selection and systematic effects.
We apply the method on a region of 7 deg$^2$ towards Cepheus OB2 and obtain 110 T-Tauri candidates with accretion rates greater than $10^{-9.5}~M_\odot$. Most of the bright candidates are confirmed by previous studies. In addition, we discover 50 new faint, low-mass candidates (r' $>$ 18.0; $M_* < 0.5~M_\odot$) which are densely clustered near the molecular clouds IC1396a and IC1396n. We show that these clouds are sites of ongoing star formation, driven by radiative implosion due to the massive star system HD206267A (O6.5V) at a distance of 5 to 15 pc. In contrast, within 2.5 pc from these hot stars we observe a decrease of accretion rates, which may be due to the destructive effects of UV-photoevaporation. Finally, we use our statistical sample to test recent claims on the steep dependency of accretion rates on stellar mass, and find that this dependency is largely due to selection and systematic effects.