In very few scientific fields, color matters more than in Astronomy. First photographic plates, and later CCDs, capture the light of distant objects by integrating during long exposures. When photons hit the CCD, small electric currents record the light intensity. Current CCDs working in the optical, UV and NIR range are basically insensitive to the “color” of the arriving light and filters need to be placed in front of the CCD to select the spectral range, or color, that wants to be studied. Often, these filters are “wide” in the sense that they allow a generous amount of light to go through (since distant objects tend to be faint), and the entire optical spectrum can be covered with 3 filters. However, their are situations where much narrower filters would be desirable. Astronomical objects tend to emit light in a combination of continuum (free-electrons being captured by the atoms) and spectral lines (electrons jumping between atomic levels). The spectral lines carry very valuable information about the conditions (like temperature and metallicity or abundance of elements heavier than Helium) that get diluted when observing the objects with wide bands. On the other hand, sufficiently narrow bands can resolve these spectral features.
Today (July 7th 2020) we published the first results of the J-PAS survey pathfinder (or miniJPAS). J-PAS is a narrow band survey of 15% of the sky, with an unprecedented number of narrow band filters (54). The image below shows the 54 narrow-band filters, plus 5 of the wide-band filters.
Using the narrow-band filters, J-PAS can identify features as the H-alpha line, or the 4000 Angstrom break, allowing for precise SED fittings and photometric redshifts of all galaxies in the catalog.
J-PAS will be particularly powerful at detecting rare objects with string emission lines. Chief among these, high redshift quasars, where the bright Lyman-alpha gets redshifted into the J-PAS spectral range, allowing for unambiguous estimation of the quasar redshifts. Earlier estimations suggest that J-PAS will be capable of detecting half a million quasars in the surveyed area.
The superior power of J-PAS to estimate photometric redshifts will open the door also to do tomographic studies and unveil the 3D structure of the galaxy distribution to unprecedented detail. Stay tunned for more. First light of the full scientific survey is expected to take place in late 2020 or early 2021. You can also find the first data release in J-PAS website and explore the images directly from your browser using the Sky Navigator
You can find the paper below and in this link https://arxiv.org/pdf/2007.01910.pdf