J-PAS: The Javalambre-Physics of the Accelerated Universe Astrophysical Survey

TL;DR

J-PAS outlines a novel narrow-band, wide-field survey strategy designed to deliver high-precision photometric redshifts and an unprecedented 3D map of the Northern Sky. By employing a contiguous set of ~56 filters with ~145 Å width, the survey achieves radial BAO measurements and multi-tracer analyses (LRG, ELG, QSOs) over $z\lesssim1.3$, while also enabling weak and strong lensing, SN, cluster, and multi-wavelength studies. The paper details the filter design, observing strategy, survey area optimization, and the empirical mocks used to forecast cosmological constraints, including neutrino masses, curvature, and the dark energy FoM, as well as the self-contained calibration plan anchored by J-PLUS. It further outlines J-PAS’s extensive galaxy evolution science, stellar populations, AGN demographics, high-redshift populations (LAEs/LBGs/DLAs), and synergy with upcoming surveys (e.g., Euclid, LSST), highlighting the survey’s potential to constrain fundamental physics and transform our understanding of structure formation. The project also introduces the hardware infrastructure (JST/T250 and JAST/T80, JPCam and T80Cam), data management architecture, and governance necessary to realize a multi-year, multi-facility astronomical endeavor. Overall, J-PAS promises transformative cosmological and astrophysical insights via an efficient, cost-effective “redshift machine” that leverages time-domain information and spectral resolution to extract a wealth of science from a single dataset.

Abstract

The Javalambre-Physics of the Accelerated Universe Astrophysical Survey (J-PAS) is a narrow band, very wide field Cosmological Survey to be carried out from the Javalambre Observatory in Spain with a purpose-built, dedicated 2.5m telescope and a 4.7 sq.deg. camera with 1.2Gpix. Starting in late 2015, J-PAS will observe 8500sq.deg. of Northern Sky and measure $0.003(1+z)$ photo-z for $9\times10^7$ LRG and ELG galaxies plus several million QSOs, sampling an effective volume of $\sim 14$ Gpc$^3$ up to $z=1.3$ and becoming the first radial BAO experiment to reach Stage IV. J-PAS will detect $7\times 10^5$ galaxy clusters and groups, setting constrains on Dark Energy which rival those obtained from its BAO measurements. Thanks to the superb characteristics of the site (seeing ~0.7 arcsec), J-PAS is expected to obtain a deep, sub-arcsec image of the Northern sky, which combined with its unique photo-z precision will produce one of the most powerful cosmological lensing surveys before the arrival of Euclid. J-PAS unprecedented spectral time domain information will enable a self-contained SN survey that, without the need for external spectroscopic follow-up, will detect, classify and measure $σ_z\sim 0.5\%$ redshifts for $\sim 4000$ SNeIa and $\sim 900$ core-collapse SNe. The key to the J-PAS potential is its innovative approach: a contiguous system of 54 filters with $145Å$ width, placed $100Å$ apart over a multi-degree FoV is a powerful "redshift machine", with the survey speed of a 4000 multiplexing low resolution spectrograph, but many times cheaper and much faster to build. The J-PAS camera is equivalent to a 4.7 sq.deg. "IFU" and it will produce a time-resolved, 3D image of the Northern Sky with a very wide range of Astrophysical applications in Galaxy Evolution, the nearby Universe and the study of resolved stellar populations.

Figures (70)

• Figure 1: The J-PAS filter system. We have included the redshifted spectrum of an early type galaxy at z=1.0 from Polleta et al. 2007. The filters are spaced by about 100 Å but have FWHM of $145~\AA$, what produces a significant overlap among them. The blue squares represent the flux which would be observed through the filters. Note that many spectral features apart from the 4000 Å break are resolved, that is why the precision in redshift is much larger than that which would be produced by a single break, $\Delta z/(1+z) \sim \Delta\lambda/\lambda \sim 0.02$
• Figure 2: Sky background used to generate our mocks, calculated averaging over the solar (2015.5-2021) and moon cycles (26 darkest nights) for a 1.2 airmass. For reference we include the airmass-corrected measurement of the sky background at the OAJ (dashed line) and the sky that our model would predict at 7 nights from the dark moon at the solar maximum (dash-dot line)
• Figure 3: Limiting AB magnitudes ($5\sigma$, 3 arcsec aperture) for all the filters in the survey, color coded by their tray distribution
• Figure 4: (Top) Visibility from OAJ. (Red, yellow, green, cyan, blue) correspond to visibilities greater than (0, 30, 100, 300, 1000) hours/year. Magenta lines represent galactic latitudes $b=(0\hbox{$^\circ$}, 30\hbox{$^\circ$}, 60\hbox{$^\circ$})$, and black lines represent declinations $\delta=(0\hbox{$^\circ$}, 30\hbox{$^\circ$}, 60\hbox{$^\circ$})$. (Middle) Dust column in each direction, as measured by Schlegel et al. (1998). The color scale (black, red, yellow, green, cyan, blue, magenta) corresponds to values of E(B-V) $>$ (0.00, 0.03, 0.10, 0.30, 1.00, 3.00, 10.00). (Bottom) Corrected visibility as described in the text. All colors and lines are the same as in the top panel.
• Figure 5: (Left) Corrected visibility plotted using equatorial coordinates. Colors are the same as those in Figure \ref{['OAJ-observability']}. (Right) Corrected visibility projected for the northern celestial hemisphere. Notice that this projection does not show the area below $\delta=0\hbox{$^\circ$}$.