EPoS Contribution
EPoS Contribution
Tracing the structure of the Perseus Arm with IPHAS

Roberto Raddi
Hatfield, UK
Research aiming to describe the morphology of our Galaxy is heavily affected by the interstellar extinction which is a natural consequence of the Solar System's location with respect to the Galactic plane. Since the earliest studies, spiral structure tracers have been taken to be H~II regions, OB associations and molecular clouds. The Perseus Arm appears to be a clear feature of the Milky Way and its distance is estimated to be between 2 and 3 kpc from the Sun. Recent trigonometric parallax measurements place the complex of molecular clouds W3/W4/W5, belonging to the arm, at a distance of ~ 2 kpc. In this context, our approach is to analyse the 3-Dimensional structure and reddening along the line of sight in a section of the Perseus Arm, between Galactic Longitudes (120, 140) and Galactic Latitudes (-1, +4). We make use of the uniform photometry obtained across the area (to r'~20) by the Isaac Newton Telescope (INT) Photometric Halpha Survey of the Northern Galactic Plane (IPHAS) to determine intrinsic colours, distances and extinctions for selected spectral types, using the extinction mapping algorithm MEAD. We compare A stars (typically ~ 10-100 Myrs old) with F star densities, to analyse evidence of young structures defined in the space in a new way. Our results are compared with simulations and other observative works.
Collaborators:
S.E. Sale, Imperial College, UK
J.E. Drew, U of Hertfordshire, UK
The IPHAS Consortium
Key publication

Suggested Session: Molecular Clouds