The INT Photometric H  Survey of the Northern Galactic Plane (IPHAS)

Abstract

The Isaac Newton Telescope (INT) Photometric Hα Survey of the Northern Galactic Plane (IPHAS) is a 1800‐deg2 CCD survey of the northern Milky Way spanning the latitude range −5° < b < + 5° and reaching down to r′≃ 20 (10σ). Representative observations and an assessment of point‐source data from IPHAS, now underway, are presented. The data obtained are Wide Field Camera images in the Hα narrow‐band, and Sloan r′ and i′ broad‐band filters. We simulate IPHAS (r′−Hα, r′−i′) point‐source colours using a spectrophotometric library of stellar spectra and available filter transmission profiles: this defines the expected colour properties of (i) solar metallicity stars, without Hα emission, and (ii) emission‐line stars. Comparisons with observations of fields in Aquila show that the simulations of normal star colours reproduce the observations well for all spectral types earlier than M. A further comparison between colours synthesized from long‐slit flux‐calibrated spectra and IPHAS photometry for six objects in a Taurus field confirms the reliability of the pipeline calibration. Spectroscopic follow‐up of a field in Cepheus shows that sources lying above the main stellar locus in the (r′− Hα, r′−i′) plane are confirmed to be emission‐line objects with very few failures. In this same field, examples of Hα deficit objects (a white dwarf and a carbon star) are shown to be readily distinguished by their IPHAS colours. The role IPHAS can play in studies of spatially resolved northern Galactic nebulae is discussed briefly and illustrated by a continuum‐subtracted mosaic image of Shajn 147 (a supernova remnant, 3° in diameter). The final catalogue of IPHAS point sources will contain photometry on about 80 million objects. Used on its own, or in combination with near‐infrared photometric catalogues, IPHAS is a major resource for the study of stellar populations making up the disc of the Milky Way. The eventual yield of new northern emission‐line objects from IPHAS is likely to be an order of magnitude increase on the number already known.

A 3D extinction map of the northern Galactic plane based on IPHAS photometry

“…The INT/WFC Photometric Hα Survey of the northern Galactic Plane (IPHAS; Drew et al 2005) is the first comprehensive digital survey of the northern Galactic disc (|b| 5 • ), covering a Galactic longitude range of 30 • l 215 • . Imaging is performed in the r, i and Hα bands down to r ∼ 20.…”

A search for white dwarfs in the Galactic plane: the field and the open cluster population

“…VPHAS+ and its twin surveys in the Northern hemisphere (IPHAS, and UVEX; Drew et al 2005;Groot et al 2009) are ideal tools for the successful identification of the missing population of faint stellar remnants of low-to intermediate-mass stars in the Galactic plane. Optical follow-up spectroscopy, with moderate resolution and S/N >20, is sufficient to confirm the white dwarfs and to measure their atmospheric parameters, but higher quality data are necessary if more accurate spectroscopic parallaxes are to be sought.…”

A wealth of new planetary nebulae from the IPHAS survey

“…Pipeline data reduction and data distribution are handled by the Cambridge Astronomical Survey Unit. The main product of the survey is its point sources photometric catalogue, whose presented by Drew et al (2005), and can also be found in the IPHAS home web page at http://www.iphas.org.…”