The Javalambre Photometric Local Universe Survey (J-PLUS ) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern Hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre (OAJ). The T80Cam is a camera with a field of view of 2 deg 2 mounted on a telescope with a diameter of 83 cm, and is equipped with a unique system of filters spanning the entire optical range (3500-10 000 Å). This filter system is a combination of broad-, medium-, and narrow-band filters, optimally designed to extract the rest-frame spectral features (the 3700-4000 Å Balmer break region, Hδ, Ca H+K, the G band, and the Mg b and Ca triplets) that are key to characterizing stellar types and delivering a low-resolution photospectrum for each pixel of the observed sky. With a typical depth of AB ∼21.25 mag per band, this filter set thus allows for an unbiased and accurate characterization of the stellar population in our Galaxy, it provides an unprecedented 2D photospectral information for all resolved galaxies in the local Universe, as well as accurate photo-z estimates (at the δ z/(1 + z) ∼ 0.005-0.03 precision level) for moderately bright (up to r ∼ 20 mag) extragalactic sources. While some narrow-band filters are designed for the study of particular emission features ([O ii]/λ3727, Hα/λ6563) up to z < 0.017, they also provide well-defined windows for the analysis of other emission lines at higher redshifts. As a result, J-PLUS has the potential to contribute to a wide range of fields in Astrophysics, both in the nearby Universe (Milky Way structure, globular clusters, 2D IFU-like studies, stellar populations of nearby and moderate-redshift galaxies, clusters of galaxies) and at high redshifts (emission-line galaxies at z ≈ 0.77, 2.2, and 4.4, quasi-stellar objects, etc.). With this paper, we release the first ∼1000 deg 2 of J-PLUS data, containing about 4.3 million stars and 3.0 million galaxies at r < 21 mag. With a goal of 8500 deg 2 for the total J-PLUS footprint, these numbers are expected to rise to about 35 million stars and 24 million galaxies by the end of the survey.Article published by EDP Sciences A176, page 1 of 25
The Observatorio Astrofísico de Javalambre (OAJ) is a new Spanish astronomical facility particularly designed for carrying out large sky surveys. The OAJ is mainly motivated by the development of J-PAS, the Javalambre-PAU Astrophysical Survey, an unprecedented astronomical survey that aims to observe 8500 deg 2 of the sky with a set of 54 optical contiguous narrow-band filters (FWHM∼14 nm) and 5 mid and broad-band ones. J-PAS will provide a low resolution spectrum (R∼50) for every pixel of the Northern sky down to AB∼22.5 − 23.5 per square arcsecond (at 5σ level), depending on the narrow-band filter, and ∼ 2 magnitudes deeper for the redder broad-band filters. The main telescope at the OAJ is the Javalambre Survey Telescope (JST/T250), an innovative Ritchey-Chrétien, alt-azimuthal, large-etendue telescope with a primary mirror diameter of 2.55 m and 3 deg (diameter) FoV. The JST/T250 is the telescope devoted to conduct J-PAS with JPCam, a panoramic camera of 4.7 deg 2 FoV and a mosaic of 14 large format CCDs that, overall, amounts to 1.2 Gpix. The second largest telescope at the OAJ is the Javalambre Auxiliary Survey Telescope (JAST/T80), a Ritchey-Chrétien, german-equatorial telescope of 82 cm primary mirror and 2 deg FoV, whose main goal is to perform J-PLUS, the Javalambre Photometric Local Universe Survey. J-PLUS will cover the same sky area of J-PAS using the panoramic camera T80Cam with 12 filters in the optical range, which are specifically defined to perform the photometric calibration of J-PAS.The OAJ project officially started in mid 2010. Four years later, the OAJ is mostly completed and the first OAJ operations have already started. The civil work and engineering installations are finished, including the telescope buildings and the domes. JAST/T80 is at the OAJ undertaking commissioning tasks, and JST/T250 is in AIV phase at the OAJ. Related astronomical subsystems like the seeing and atmospheric extinction monitors and the all-sky camera are fully operative. This paper aims to present a brief description and status of the OAJ main installations, telescopes and cameras. The current development and operation plan of the OAJ in terms of staffing organization, resources, observation scheduling, and data archiving, is also described.
Received Month X, XXXX; revised Month X, XXXX; accepted Month X, XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX The Zernike power spectra of the all-sky night brightness distributions of clear and cloudy nights are computed using a modal projection approach. The results obtained in the B, V and R Johnson-Cousins' photometric bands during a one-year campaign of observations at a light-polluted urban site show that these spectra can be described by simple power laws with exponents close to −3 for clear nights and −2 for cloudy ones. The second-moment matrices of the Zernike coefficients show relevant correlations between modes. The multiplicative role of the cloud cover, that contributes to a significant increase of the brightness of the urban night sky in comparison with the values obtained in clear nights, is described in the Zernike space. 1.IntroductionThe constant increase of the sky glow produced by the anthropogenic emissions of light is one unwanted side-effect of the continuous spread of public and private lighting systems. A considerable amount of research is being devoted to the measurement and characterization of this phenomenon, in order to get reliable data for modeling accurately its propagation [1−6], to understand better its consequences in diverse fields [7−14], and to devise practicable strategies to keep it within acceptable limits [15−16].The multiplicative role of the cloud cover is also a matter of concern. Clouds greatly enhance the night sky brightness by reflecting (scattering) the upward radiation of the city lights. Urban overcast skies may reach radiances an order of magnitude higher than the corresponding clear skies, and four times bigger than rural clear moonlit nights [17−19]. Overall, the present levels of light pollution in many places across the world amount to a substantial change in the natural conditions of the nighttime environment.A widespread technique for monitoring the night sky brightness is based on the use of all-sky cameras with hemispheric field-of-view [20−23] that record with good spatial resolution the sky radiance in standard astronomical photometric bands like the B, V, and R Johnson-Cousins' set [24]. In a previous work [25] we have shown that the all-sky night brightness maps obtained in clear and moonless nights can be efficiently described in terms of Zernike polynomials [26−27]. Using this approach the information content of each map is condensed into an equivalent small-sized vector whose elements (the Zernike coefficients) have a definite physical meaning.Besides achieving a significant level of essentially lossless data compression, the study of the hemispherical night sky brightness may benefit that way from the conceptual and computational tools associated with modal analysis.As an example of application we described in that work the modal composition of clear and moonless urban night skies in the range of low to mid Zernike frequencies (radial orders 10 ≤ n ). While an expansion up to this order is generally enough for a succes...
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