The production of the catalogue, IPHAS DR2 (the second release from the survey programme The INT Photometric H-alpha Survey of the Northern Galactic Plane or IPHAS), is an example of modern astronomy's exploitation of 'big data' – it contains information on the 219 million detected objects, each of which is summarised in 99 attributes.
With this catalogue release, the team are offering the world community free access to measurements taken through two broad band filters capturing light at the red end of the visible spectrum, and in a narrowband capturing the brightest hydrogen emission line, H-alpha. The inclusion of H-alpha also enables exquisite imaging of the nebulae (glowing clouds of gas) found in greatest number within the disk of the Milky Way. The stellar density map illustrated here is derived from the longest (reddest) wavelength band in which the darkening effect of the dust is moderated in a way that brings out more of its structural detail, compared to maps built at shorter (bluer) wavelengths.
Dr Geert Barentsen
University of Hertfordshire
Tel: +44 (0)17 0728 4603
Mob: +44 (0)75 4700 3148
Prof Janet Drew
University of Hertfordshire
Tel: +44 (0)1707 286576
Mob: +44 (0)7758 918823
The new work appears in Barentsen et al, 2014, "The second data release of the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS DR2)", Monthly Notices of the Royal Astronomical Society, 444, 3230, published by Oxford University Press. A preprint version is available on the arXiv server.
The catalogue is accessible in queryable form via the VizieR service at the Centre de Données astronomiques de Strasbourg. The processed IPHAS images it is derived from are also publically available. The preparation of the catalogue was funded by the Science and Technology Facilities Council.
IPHAS is the acronym standing for "The INT Photometric H-alpha Survey of the Northern Galactic Plane" (see the IPHAS survey website). IPHAS, in combination with its follow-on sister survey UVEX, imaging the Milky Way using complementary blue filters, has used the Wide Field Camera on the INT in observing campaigns stretching over more than 500 allocated nights since August 2003. Together with another survey, VPHAS+, now in progress on a telescope in Chile, these ambitious observational programmes are collectively known as the European Galactic Plane Surveys (EGAPS). They are exploiting modern high-resolution CCD imaging technology and the growth in computing power to map the entire disk of our galaxy in visible light and at high angular resolution for the first time.
Recently reported results derived from IPHAS survey data include a 3-D reconstruction of the distribution of dust across the Milky Way's disk (Sale et al. 2014, MNRAS, 443, 2907) and the discovery of 159 new planetary nebulae (Sabin et al. 2014, MNRAS, 443, 3388).