Publications

Publications

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 deg2 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 deg2 of J-PLUS data, containing about 4.3 million stars and 3.0 million galaxies at r <  21 mag. With a goal of 8500 deg2 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.

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Aims: Our goal is to morphologically classify the sources identified in the images of the J-PLUS early data release (EDR) as compact (stars) or extended (galaxies) using a dedicated Bayesian classifier. Methods: J-PLUS sources exhibit two distinct populations in the r-band magnitude versus concentration plane, corresponding to compact and extended sources. We modelled the two-population distribution with a skewed Gaussian for compact objects and a log-normal function for the extended objects. The derived model and the number density prior based on J-PLUS EDR data were used to estimate the Bayesian probability that a source is a star or a galaxy. This procedure was applied pointing-by-pointing to account for varying observing conditions and sky positions. Finally, we combined the morphological information from the g, r, and i broad bands in order to improve the classification of low signal-to-noise sources. Results: The derived probabilities are used to compute the pointing-by-pointing number counts of stars and galaxies. The former increases as we approach the Milky Way disk, and the latter are similar across the probed area. The comparison with SDSS in the common regions is satisfactory up to r 21, with consistent numbers of stars and galaxies, and consistent distributions in concentration and (g-i) colour spaces. Conclusions: We implement a morphological star/galaxy classifier based on probability distribution function analysis, providing meaningful probabilities for J-PLUS sources to one magnitude deeper (r 21) than a classical Boolean classification. These probabilities are suited for the statistical study of 150 thousand stars and 101 thousand galaxies with 15 < r ≤ 21 present in the 31.7 deg2 of the J-PLUS EDR. In a future version of the classifier, we will include J-PLUS colour information from 12 photometric bands.

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Aims: We aim to use multiband imaging from the Phase-3 Verification Data of the J-PLUS survey to derive accurate photometric redshifts (photo-z) and look for potential new members in the surroundings of the nearby galaxy clusters A2589 (z = 0.0414) & A2593 (z = 0.0440), using redshift probability distribution functions (PDFs). The ultimate goal is to demonstrate the usefulness of a 12-band filter system in the study of largescale structure in the local Universe. Methods: We present an optimized pipeline for the estimation of photometric redshifts in clusters of galaxies. This pipeline includes a PSF-corrected photometry, specific photometric apertures capable of enhancing the integrated signal in the bluest filters, a careful recalibration of the photometric uncertainties and accurate upper-limit estimations for faint detections. To foresee the expected precision of our photo-z beyond the spectroscopic sample, we designed a set of simulations in which real cluster galaxies are modeled and reinjected inside the images at different signal-to-noise ratio (S/N) levels, recomputing their photometry and photo-z estimates. Results: We tested our photo-z pipeline with a sample of 296 spectroscopically confirmed cluster members with an averaged magnitude of ⟨r⟩ = 16.6 and redshift ⟨z⟩ = 0.041. The combination of seven narrow and five broadband filters with a typical photometric-depth of r 21.5 provides δz/(1 + z) = 0.01 photo-z estimates. A precision of δz/(1 + z) = 0.005 is obtained for the 177 galaxies brighter than magnitude r < 17. Based on simulations, a δz/(1 + z) = 0.02 and δz/(1 + z) = 0.03 is expected at magnitudes ⟨r⟩ = 18 and ⟨r⟩ = 22, respectively. Complementarily, we used SDSS/DR12 data to derive photo-z estimates for the same galaxy sample. This exercise demonstrates that the wavelength-resolution of the J-PLUS data can double the precision achieved by SDSS data for galaxies with a high S/N. Based on the Bayesian membership analysis carried out in this work, we find as much as 170 new candidates across the entire field ( 5 deg2). The spatial distribution of these galaxies may suggest an overlap between the systems with no evidence of a clear filamentary structure connecting the clusters. This result is supported by X-ray Rosat All-Sky Survey observations suggesting that a hypothetical filament may have low density contrast on diffuse warm gas. Conclusions: We prove that the addition of the seven narrow-band filters make the J-PLUS data deeper in terms of photo-z-depth than other surveys of a similar photometric-depth but using only five broadbands. These preliminary results show the potential of J-PLUS data to revisit membership of groups and clusters from nearby galaxies, important for the determination of luminosity and mass functions and environmental studies at the intermediate and low-mass regime.

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Context. As a consequence of internal and external dynamical processes, Galactic globular clusters (GCs) have properties that vary radially. Wide-field observations covering the entire projected area of GCs out to their tidal radii (rtidal) can therefore give crucial information on these important relics of the Milky Way formation era. Aims: The Javalambre Photometric Local Universe Survey (J-PLUS) provides wide field-of-view (2 deg2) images in 12 narrow, intermediate and broad-band filters optimized for stellar photometry. Here we have applied J-PLUS data for the first time for the study of Galactic GCs using science verification data obtained for the very metal-poor ([Fe/H] ≈-2.3) GC M 15 located at 10 kpc from the Sun. Previous studies based on spectroscopy found evidence of multiple stellar populations (MPs) through their different abundances of C, N, O, and Na. Our J-PLUS data provide low-resolution spectral energy distributions covering the near-UV to the near-IR, allowing us to instead search for MPs based on pseudo-spectral fitting diagnostics. Methods: We have built and discussed the stellar radial density profile (RDP) and surface brightness profiles (SBPs) reaching up to rtidal. Since J-PLUS FoV is larger than M 15's rtidal, the field contamination can be properly taken into account. We also demonstrated the power of J-PLUS unique filter system by showing colour-magnitude diagrams (CMDs) using different filter combinations and for different cluster regions. Results: J-PLUS photometric quality and depth are good enough to reach the upper end of M 15's main-sequence. CMDs based on the colours (u - z) and (J0378 - J0861) are found to be particularly useful to search for splits in the sequences formed by the upper red giant branch (RGB) and asymptotic giant branch (AGB) stars. We interpret these split sequences as evidence for the presence of MPs. Furthermore, we show that the (u - z) × (J0378 - g) colour-colour diagram allows us to distinguish clearly between field and M 15 stars, which is important to minimize the sample contamination. Conclusions: The J-PLUS filter combinations (u - z) and (J0378 - J0861), which are sensitive to metal abundances, are able to distinguish different sequences in the upper RGB and AGB regions of the CMD of M 15, showing the feasibility of identifying MPs without the need of spectroscopy. This demonstrates that the J-PLUS survey will have sufficient spatial coverage and spectral resolution to perform a large statistical study of GCs through multi-band photometry in the coming years.

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In this paper we aim to validate a methodology designed to obtain Hα emission line fluxes from J-PLUS photometric data. J-PLUS is a multi narrow-band filter survey carried out with the 2 deg2 field of view T80Cam camera, mounted on the JAST/T80 telescope in the OAJ, Teruel, Spain. The information of the twelve J-PLUS bands, including the J0660 narrow-band filter located at rest-frame Hα, is used over the first 42 deg2 observed to retrieve de-reddened and [NII] decontaminated Hα emission line fluxes of 46 star-forming regions with previous SDSS and/or CALIFA spectroscopic information. The agreement between the J-PLUS Hα fluxes and those obtained with spectroscopic data is remarkable, finding a median comparison ratio with a scatter of R = FJ-PLUSHα/FspecHα = 1.05 ± 0.25 . This demonstrates that it is possible to retrieve reliable Hα emission line fluxes from J-PLUS photometric data. With an expected area of thousands of square degrees upon completion, the J-PLUS dataset will allow the study of several star formation science cases in the nearby universe, as the spatially resolved star formation rate of nearby galaxies at z ≤ 0.015, and how it is influenced by the environment, morphology, stellar mass, and nuclear activity. As an illustrative example, the close pair of interacting galaxies NGC 3994 and NGC 3995 is analysed, finding an enhancement of the star formation rate not only in the centre, but also in outer parts of the disk of NGC 3994.

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Context. The spatial variations of stellar population properties within a galaxy are intimately related to their formation process. Therefore, spatially resolved studies of galaxies are essential to uncover their formation and assembly. Although the arrival of integral field unit (IFU) surveys has brought a significant breakthrough in the field, recent techniques that combine photometric multifilter surveys with spectral fitting diagnostics have opened a new, relatively low-cost way to disentangle the stellar population of spatially resolved galaxies compared to IFU surveys. Aims: The Javalambre Photometric Local Universe Survey (J-PLUS) is a dedicated multifilter designed to observed ˜8500 deg2 of the northern sky using 12 narrowband, intermediate-band, and broadband filters in the optical range. In this study, we test the potential of the multifilter observation carried out with J-PLUS to investigate the properties of spatially resolved nearby galaxies. Methods: We present detailed 2D maps of stellar population properties, i.e., age, metallicity, extinction, and stellar mass surface density, for two early-type galaxies observed in the J-PLUS and CALIFA surveys. These galaxies are NGC 5473 and NGC 5485. Radial structures are also compared and luminosity- and mass-weighted profiles are derived. We use MUFFIT to process the J-PLUS photometric multifilter observations, and STARLIGHT and STECKMAP to analyze IFU CALIFA data. Results: We demonstrate the scientific potential of J-PLUS/MUFFIT to explore the spatially resolved stellar populations of local galaxies. We find significant discrepancies between the results from the various analysis methods. While radial stellar population gradients obtained with J-PLUS/MUFFIT and the IFU technique CALIFA/STECKMAP are more in agreement, radial stellar population gradients largely differ when CALIFA/STARLIGHT methodology is used. A comparison of the absolute values reveals the existence of intrinsic systematic differences. Age and metallicity radial profiles derived from J-PLUS/MUFFIT are very similar when luminosity- or mass-weighted properties are used, suggesting that the contribution of a younger component is small and the star formation history of these early-type galaxies are well represented by mainly an old single stellar population component. Conclusions: We present the potential of J-PLUS to explore the unresolved stellar populations of spatially extended local galaxies. A comparison between the three methodologies reveals some discrepancies suggesting that the specific characteristics of each method causes important differences. We conclude that the ages, metallicities, and extinction derived for individual galaxies not only depend on the chosen models but also depend on the method used. Future work is required to evaluate in detail the origin of these differences and to quantify the impact that different fitting routines have on the derived stellar population properties.

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Context. We present a new methodology for the estimation of stellar atmospheric parameters from narrow- and intermediate-band photometry of the Javalambre Photometric Local Universe Survey (J-PLUS), and propose a method for target pre-selection of low-metallicity stars for follow-up spectroscopic studies. Photometric metallicity estimates for stars in the globular cluster M15 are determined using this method. Aims: By development of a neural-network-based photometry pipeline, we aim to produce estimates of effective temperature, Teff, and metallicity, [Fe/H], for a large subset of stars in the J-PLUS footprint. Methods: The Stellar Photometric Index Network Explorer, SPHINX, was developed to produce estimates of Teff and [Fe/H], after training on a combination of J-PLUS photometric inputs and synthetic magnitudes computed for medium-resolution (R 2000) spectra of the Sloan Digital Sky Survey. This methodology was applied to J-PLUS photometry of the globular cluster M15. Results: Effective temperature estimates made with J-PLUS Early Data Release photometry exhibit low scatter, σ(Teff) = 91 K, over the temperature range 4500 < Teff (K) < 8500. For stars from the J-PLUS First Data Release with 4500 < Teff (K) < 6200, 85 ± 3% of stars known to have [Fe/H] < -2.0 are recovered by SPHINX. A mean metallicity of [Fe/H] = - 2.32 ± 0.01, with a residual spread of 0.3 dex, is determined for M15 using J-PLUS photometry of 664 likely cluster members. Conclusions: We confirm the performance of SPHINX within the ranges specified, and verify its utility as a stand-alone tool for photometric estimation of effective temperature and metallicity, and for pre-selection of metal-poor spectroscopic targets.

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Context. The intracluster light (ICL) is a luminous component of galaxy clusters composed of stars that are gravitationally bound to the cluster potential, but do not belong to the individual galaxies. Previous studies of the ICL have shown that its formation and evolution are intimately linked to the evolutionary stage of the cluster. Thus, the analysis of the ICL in the Coma cluster will give insights into the main processes driving the dynamics in this highly complex system. Aims: Using a recently developed technique, we measure the ICL fraction in Coma at several wavelengths, using the J-PLUS unique filter system. The combination of narrow- and broadband filters provides valuable information on the dynamical state of the cluster, the ICL stellar types, and the morphology of the diffuse light. Methods: We used the Chebyshev-Fourier intracluster light estimator (CICLE) to distinguish the ICL from the light of the galaxies, and to robustly measure the ICL fraction in seven J-PLUS filters. Results: We obtain the ICL fraction distribution of the Coma cluster at different optical wavelengths, which varies from ˜7%-21%, showing the highest values in the narrowband filters J0395, J0410, and J0430. This ICL fraction excess is a distinctive pattern that has recently been observed in dynamically active clusters (mergers), indicating a higher amount of bluer stars in the ICL than in cluster galaxies. Conclusions: The high ICL fractions and the excess in the bluer filters are indicative of a merging state. The presence of younger stars or stars with lower metallicity in the ICL suggests that the main mechanism of ICL formation for the Coma cluster is the stripping of the stars in the outskirts of infalling galaxies and possibly the disruption of dwarf galaxies during past or ongoing mergers.

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