J-PAS: Measuring emission lines with artificial neural networks

Abstract

In the years to come, the Javalambre-Physics of the Accelerated Universe Astrophysical Survey (J-PAS) will observe 8000 deg2 of the northern sky with 56 photometric bands. J-PAS is ideal for the detection of nebular emission objects. This paper presents a new method based on artificial neural networks (ANNs) that is aimed at measuring and detecting emission lines in galaxies up to z = 0.35. These lines are essential diagnostics for understanding the evolution of galaxies through cosmic time. We trained and tested ANNs with synthetic J-PAS photometry from CALIFA, MaNGA, and SDSS spectra. To this aim, we carried out two tasks. First, we clustered galaxies in two groups according to the values of the equivalent width (EW) of Hα, Hβ, [N II], and [O III] lines measured in the spectra. Then we trained an ANN to assign a group to each galaxy. We were able to classify them with the uncertainties typical of the photometric redshift measurable in J-PAS. Second, we utilized another ANN to determine the values of those EWs. Subsequently, we obtained the [N II]/Hα, [O III]/Hβ, and O 3N 2 ratios, recovering the BPT diagram ([O III]/Hβ versus [N II]/Hα). We studied the performance of the ANN in two training samples: one is only composed of synthetic J-PAS photo-spectra (J-spectra) from MaNGA and CALIFA (CALMa set) and the other one is composed of SDSS galaxies. We were able to fully reproduce the main sequence of star-forming galaxies from the determination of the EWs. With the CALMa training set, we reached a precision of 0.092 and 0.078 dex for the [N II]/Hα and [O III]/Hβ ratios in the SDSS testing sample. Nevertheless, we find an underestimation of those ratios at high values in galaxies hosting an active galactic nuclei. We also show the importance of the dataset used for both training and testing the model. Such ANNs are extremely useful for overcoming the limitations previously expected concerning the detection and measurements of the emission lines in such surveys as J-PAS. Furthermore, we show the capability of the method to measure a EW of 10 Å in Hα, Hβ, [N II] and [O III] lines with a signal-to-noise ratio (S/N) of 5, 1.5, 3.5, and 10, respectively, in the photometry. Finally, we compare the properties of emission lines in galaxies observed with miniJPAS and SDSS. Despite the limitation of such a comparison, we find a remarkable correlation in their EWs.

Black hole virial masses from single-epoch photometry: the miniJPAS test case

“…The J-PAS filter system 2 (Brauneck et al 2018a,b) was designed to provide accurate photometric redshifts for both blue and red galaxies up to 𝑧 ∼ 1 (Benítez et al 2009;Benitez et al 2014), and for quasars up to 𝑧 6 (Abramo et al 2012;Chaves-Montero et al 2017). The first results from miniJPAS confirmed the expectations of sub-percent photo-𝑧 precision (Bonoli et al 2021b;Hernán-Caballero et al 2021), the potential of the J-PAS filter system to detect and characterise emission line sources (Bonoli et al 2021b;González Delgado et al 2021;Martínez-Solaeche et al 2021), and more specifically to capture the main features of low redshift quasars (Bonoli et al 2021a) using (Calderone et al 2017). Furthermore, the WEAVE-QSO survey (Pieri et al 2016) will follow-up with high spectral resolution ∼ 400𝑘 J-PAS quasars at 𝑧 > 2, allowing to further test and calibrate our approach.…”

“…In addition, photometric redshifts from broad-band photometry do not present enough precision for unambiguous line identification. The emergence of medium-and narrow-band photometric surveys continuously covering a large wavelength range such as the Subaru COSMOS 20 survey (Taniguchi et al 2015;Sobral et al 2018), the Advance Large Homogeneous Area Medium Band Redshift Astronomical survey (ALHAMBRA; Moles et al 2008), the NEWFIRM Medium-Band Survey (NMBS; van Dokkum et al 2009), the Survey for High-z Ab-sorption Red and Dead Sources (SHARDS; Pérez-González et al 2013), the Physics of the Accelerating Universe Survey (PAUS; Eriksen et al 2019), and the Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS; Benitez et al 2014) are progressively changing this picture, as multi-band photometric surveys first reached enough spectral resolution to detect broad emission lines (Chaves-Montero et al 2017;Lumbreras-Calle et al 2019), and then to detect narrow lines and resolve the profile of broad lines approximately (Alarcon et al 2021;Bonoli et al 2021b;Martínez-Solaeche et al 2021).…”

The miniJPAS survey quasar selection I: Mock catalogues for classification

“…Chaves-Montero et al 2017) and machine learning algorithms (ML; e.g. Golob et al 2021;Martínez-Solaeche et al 2021;Nakazono et al 2021).…”

Black hole virial masses from single-epoch photometry

“…The emergence of medium-and narrow-band photometric surveys continuously covering a large wavelength range, such as the Subaru Cosmic Evolution Survey 20 (Subaru COS-MOS 20; Taniguchi et al 2015;Sobral et al 2018), the Advance Large Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey (Moles et al 2008), the National Optical Astronomy Observatory (NOAO) Extremely Wide-Field Infrared Imager (NEWFIRM) Medium-Band Survey (NMBS; van Dokkum et al 2009), the Survey for High-z Absorption Red and Dead Sources (SHARDS; Pérez-González et al 2013), the Physics of the Accelerating Universe Survey (PAUS; Eriksen et al 2019), and the Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS; Benitez et al 2014), is progressively changing this picture. Multi-band photometric surveys have reached high enough spectral resolution to first detect broad emission lines (Chaves-Montero et al 2017;Lumbreras-Calle et al 2019) and then detect narrow lines and approximately resolve the profile of broad lines (Alarcon et al 2021;Martínez-Solaeche et al 2021).…”