Star-forming galaxies at low-redshift in the SHARDS survey

Abstract

Context. The physical processes driving the evolution of star formation (SF) in galaxies over cosmic time still present many open questions. Recent galaxy surveys allow now to study these processes in great detail at intermediate redshift (0 ≤ z ≤ 0.5). Aims. We build a complete sample of star-forming galaxies and analyze their properties, reaching systems with low stellar masses and low star formation rates (SFRs) at intermediate-to-low redshift. Methods. We use data from the SHARDS multiband survey in the GOODS-North field. Its depth (up to magnitude m 3σ ∼ 26.5) and its spectro-photometric resolution (R ∼ 50) provides us with an ideal dataset to search for emission line galaxies (ELGs). We develop a new algorithm to identify low-redshift (z<0.36) ELGs by detecting the [OIII]5007 and Hα emission lines simultaneously. We fit the spectral energy distribution (SED) of the selected sample, using a model with two single stellar populations. Results. We find 160 star-forming galaxies for which we derive equivalent widths (EWs) and absolute fluxes of both emission lines. We detect EWs as low as 12 Å, with median values for the sample of ∼ 35 Å in [OIII]5007 and ∼ 56 Å in Hα, respectively. Results from the SED fitting show a young stellar population with low median metallicity (36% of the solar value) and extinction (A V ∼ 0.37), with median galaxy stellar mass ∼ 10 8.5 M . Gas-phase metallicities measured from available spectra are also low. ELGs in our sample present bluer colours in the UVJ plane than the median colour-selected star-forming galaxy in SHARDS. We suggest a new (V-J) colour criterion to separate ELGs from non-ELGs in blue galaxy samples. In addition, several galaxies present high densities of O-type stars, possibly producing galactic superwinds, which makes them interesting targets for follow-up spectroscopy. Conclusions. We have demonstrated the efficiency of SHARDS in detecting low-mass ELGs (∼2 magnitudes deeper than previous spectroscopic surveys in the same field). The selected sample accounts for 20% of the global galaxy population at this redshift and luminosity, and is characterized by young SF bursts with sub-solar metallicities and low extinction. However, robust fits to the full SEDs can only be obtained including an old stellar population, suggesting the young component is built up by a recent burst of SF in an otherwise old galaxy.

The most massive, passive, and oldest galaxies at 0.5 < z < 2.1: Downsizing signature from galaxies selected from MgUV index

“…Based on colormagnitude diagrams (hereafter CMD), for example U-V versus M V (Bell et al 2004), galaxies can be separated into two different categories. Late-type galaxies are known as relatively young low-mass galaxies with active star formation (Brinchmann et al 2004;Amorín et al 2017;Lumbreras-Calle et al 2019). Their spectral light is dominated by the emission of young stars in the UV.…”

A simultaneous search for high-z LAEs and LBGs in the SHARDS survey

“…The main purpose of SHARDS was to provide SEDs with good enough spectral resolution to study red and passive galaxies up to redshift z ∼ 2. Nonetheless, they can be used to detect line emitting sources that otherwise would not be detected using broader filters Rodríguez Espinosa et al 2014;Hernán-Caballero et al 2017;Lumbreras-Calle et al 2018), as well as drop-out sources that can be well characterized by the many consecutive filters. Indeed, the relative narrowness of the SHARDS filters and large number of them result in good spectrally resolved SEDs (R ∼ 50).…”

Subaru/HSC z-Broadband Excess Selection of Extreme Emission Line Galaxies at z<1

“…Techniques employing wider filters have been used to find EELGs at a variety of redshifts. At z ≤ 0.3, both intermediate-band (Hinojosa-Goñi et al 2016;Lumbreras-Calle et al 2019) and broadband (Cardamone et al 2009;Yang et al 2017) filters have been employed. Broadband filters have also been used in the optical to locate intermediate-redshift (z ∼ 0.5) samples (Li & Malkan 2018) and in the NIR to locate high-redshift (z ≥ 1.0, van der Wel et al 2011;Huang et al 2015;Tang et al 2019) and very highredshift (4 ≤ z ≤ 8, Smit et al 2015) samples.…”