The INT Photometric Hα Survey of the Northern Galactic Plane
IPHAS is a major survey of the Northern Galactic Plane being carried
out with the 2.5-metre Isaac Newton Telescope (INT) in La Palma (Drew et al. 2005). The
IPHAS survey began taking data with the INT Wide Field Camera in 2003
with the goal of imaging the entire northern galactic plane in the
latitude range -5° < b < +5 degrees. Imaging of this 1800 sq.
degree area is now almost complete, and initial data products have
been released (Gonzales-Solares et al. 2007)
The Hα spectral line is significant in that it both traces diffuse
ionised nebulae and is commonly prominent in the spectra of pre- and
post-main-sequence stars. These objects are in a minority in a galaxy
like our own due to them representing relatively short-lived phases of
evolution, yet the study of them is crucial to understanding the key
stages of stellar evolution.
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The Pelican nebula, IC 5070, imaged via the IPHAS survey
(Hα=Red/Yellow). This high resolution image shows stars at all stages of stellar evolution, including two Herbig-Haro objects, new-born stars dramatically entering the main sequence. |
Pre-main-sequence stellar objects such as T Tauri stars,
Herbig AeBe
stars and Herbig-Haro objects help determine the growth of planetary
systems. Post-main-sequence stars determine stellar end states and
contribute to the recycling of energy and chemically enriched matter
back into the ISM. These objects include supergiants, luminous blue
variables, AGB stars, post-AGB objects, planetary nebulae and
interacting binaries.
The data obtained will be mined both for spatially-resolved nebulae and
for unresolved emission line stars. For point sources, the useful
magnitude range is 13.5 < m(pv) < 20.5. Previous surveys of the
area are more than 40 years old and begin to be incomplete even at
m(V)=12.5. Preliminary results suggest that around 10,000 new Hα
emission sources will be catalogued.
This programme will complement the Southern Hα Survey (SHS), an Hα
survey of the southern galactic plane carried out photographically with
the UK Schmidt Telescope. It is expected that IPHAS will exceed this in
both sensitivity and resolution. ESO has recently selected VPHAS, an Hα
survey of the Southern Galactic Plane that will be complementary to
IPHAS and which will be carried out by the 2.5-metre VLT Survey
Telescope (VST) at Paranal in Chile.
IPHAS Observations and Data Reduction
The IPHAS survey is being carried out using the Wide Field
Camera (WFC)
on the 2.5-metre Isaac Newton Telescope (INT) in La Palma. Observations
are made using narrow band Hα, sloan r' and sloan i' filters on a
mosaic of 4 CCDs, providing a field of view of 34×34 arcmins. Each
pointing is accompanied by a second pointing at an offset position 5
arcmin W and 5 arcmin S. Data reduction is carried out by the Cambridge
Astronomical Survey Unit (CASU), where it is pipeline processed. The
pipeline calibrates the raw data, extracts sources from the Hα, r' and
i' processed images, correlates them, and produces a final merged
catalogue where astrometric and photometric information is stored. Also
available for download are the background-subtracted images of the
CCDs, available as FITS files (Flexible Image Transport System).
For more information on the IPHAS survey, visit its website.
The initial data release in December 2007 was the subject of a UCL press release.
More images produced from the IPHAS Survey are available on Nick Wright's website
UCL contact: Professor Mike Barlow (mjb AT star.ucl.ac.uk)
Page last modified on 11 apr 17 16:12 by Roger Wesson
