Initial data release from the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS)

The Isaac Newton Telescope (INT) Photometric Halpha Survey of the Northern Galactic Plane (IPHAS) is a 1800-deg 2 CCD survey of the northern Milky Way spanning the latitude range -5° < b < + 5° and reaching down to r'~= 20 (10sigma). 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 Halpha narrow-band, and Sloan r' and i' broad-band filters. We simulate IPHAS (r'-Halpha,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 Halpha 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'- Halpha,r'-i') plane are confirmed to be emission-line objects with very few failures. In this same field, examples of Halpha 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.

[1]  Mark Mueller,et al.  The 6.5-m MMT's f/5 wide-field optics and instruments , 2004, SPIE Astronomical Telescopes + Instrumentation.

[2]  M. Cohen.  Red and nebulous objects in dark clouds - A survey , 1980 .

[3]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[4]  S. Bergh,et al.  An Optical Atlas of Galactic Supernova Remnants , 1973 .

[5]  Carlos Jaschek,et al.  The classification of stars , 1987 .

[6]  M. Irwin,et al.  Automatic Analysis of Crowded Fields , 1985 .

[7]  A. Pickles.  A Stellar Spectral Flux Library: 1150–25000 Å , 1998 .

[8]  Q. Parker,et al.  PLANETARY NEBULAE: THEIR EVOLUTION AND ROLE IN THE UNIVERSE , 2003 .

[9]  D. Lamb,et al.  A Catalog of Spectroscopically Identified White Dwarf Stars in the First Data Release of the Sloan Digital Sky Survey , 2004, astro-ph/0402209.

[10]  T. Naylor.  An optimal extraction algorithm for imaging photometry , 1998 .

[11]  More Wolf-Rayet central stars of planetary nebulae identified on the AAO/UKST Hα survey , 2001 .

[12]  Andreas Kelz,et al.  Ground-based instrumentation for astronomy , 2004 .

[13]  D. Russeil,et al.  Star-forming complexes and the spiral structure of our Galaxy , 2003 .

[14]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[15]  I. Hachisu,et al.  Evolution of Rotating Accreting White Dwarfs and the Diversity of Type Ia Supernovae , 2003, astro-ph/0309433.

[16]  Q. Parker,et al.  First Results from the Combination of the AAO/UKST and Marseille Hα Surveys , 2001, Publications of the Astronomical Society of Australia.

[17]  et al,et al.  Sloan Digital Sky Survey Imaging of Low Galactic Latitude Fields: Technical Summary and Data Release , 2004, astro-ph/0409700.

[18]  M. Dopita,et al.  Planetary nebulae : their evolution and role in the universe : proceedings of the 209th symposium of the International Astronomical Union held at Canberra, Australia, 19-23 November 2001 , 2003 .

[19]  Arlo U. Landolt,et al.  UBVRI Photometric Standard Stars in the Magnitude Range 11 , 1992 .

[20]  W. Hillebrandt,et al.  Type IA Supernova Explosion Models , 2000 .

[21]  T. Jordan,et al.  Faint H-alpha emission objects near the equatorial selected areas , 1989 .

[22]  D. Hayes,et al.  Calibration of Fundamental Stellar Quantities , 1985 .

[23]  Edwin A. Valentijn,et al.  The Future of Photometric, Spectrophotometric and Polarimetric Standardization , 2007 .

[24]  Angular diameters, fluxes and extinction of compact planetary nebulae: further evidence for steeper extinction towards the bulge , 2004, astro-ph/0407173.

[25]  M. Irwin,et al.  INT WFS pipeline processing , 2001 .

[26]  I. Reid,et al.  2MASS Discoveries of Cool, Dust‐enshrouded Carbon Stars out of the Galactic Plane , 2000 .

[27]  P. Merrill,et al.  Catalogue and Bibliography of Stars of Classes B and A whose Spectra have Bright Hydrogen Lines , 1933 .

[28]  R. Joyce,et al.  A flux-limited sample of Galactic carbon stars , 1987 .

[29]  Patrick Thaddeus,et al.  A wide-latitude CO survey of molecular clouds in the northern Milky Way , 1985 .

[30]  M. Bessell,et al.  JHKLM PHOTOMETRY: STANDARD SYSTEMS, PASSBANDS, AND INTRINSIC COLORS , 1988 .

[31]  I. Howarth.  LMC and galactic extinction , 1983 .

[32]  M. Barlow,et al.  Discovery of a WO star in the Scutum—Crux arm of the inner Galaxy , 2004, astro-ph/0403482.

[33]  J. Urquhart,et al.  Erratum: A radio and mid-infrared survey of northern bright-rimmed clouds , 2004 .