arXiv subjects

David Sobral

Publications and source records attributed to David Sobral.

At least 19 recordsLinked to original sources

arXiv2026

The JWST Emission Line Survey (JELS): Multi-wavelength properties of Paschen line-emitters at Cosmic Noon

Context: Narrowband JWST/NIRCam selection isolates star-forming galaxies in well-defined redshift slices, while ALMA and archival far-IR/submm data reveal obscured growth. We combine these to measure Paschen-line SFRs, infer nebular extinction from EAZY Av, and probe FIR-to-submm emission via weighted-median stacking, to constrain galaxy growth at cosmic noon. Aims: We characterize stellar, nebular, and FIR properties of Paschen-selected galaxies in COSMOS, in two ensembles at z~1.50 (Pa-alpha) and z~2.65 (Pa-beta), quantifying short- vs long-timescale SF and dust attenuation, and constraining obscured SFR and gas masses. Methods: We select robust narrowband-excess samples from the JELS F466N/F470N mosaic (Pa-alpha: 77, Pa-beta: 31 sources), remove AGN via X-ray/radio matching, and assemble multiwavelength photometry (JWST, HST, Spitzer, Herschel, SCUBA-2, AzTEC, ALMA). Photo-z/stellar properties come from EAZY/STARDUST; line SFRs use recent Paschen calibrations, with nebular extinction from EAZY Av. Results: EAZY fits show stellar masses log(Mstar/Msun)~7.4-10.3 and modest SFRs (0.1-27 Msun/yr). Line SFRs are 0.1-22.0 and 0.7-47.9 Msun/yr for Pa-alpha/beta. Most sources show short-term bursts (line SFRs exceed SED SFRs), weakly decreasing with mass. Nebular attenuation correlates with mass and SFR. Stacking gives no >3sigma detections beyond MIRI. The weighted-median SED gives SFR_UV,med = 0.48+-0.11 and 3.92+-0.47 Msun/yr for Pa-alpha/beta. ALMA Band 4 gives the tightest constraints: median 3-sigma limits SFR_IR<53 (Pa-alpha) and <44 Msun/yr (Pa-beta); gas mass <10^11.2 (Pa-alpha) and <10^10.6 Msun (Pa-beta). Conclusions: Paschen-selected samples show widespread short-timescale star formation, but FIR/sub-mm data give only upper limits on obscured SFR/ISM mass. Deeper spectroscopy and ALMA continuum data are needed to constrain obscured SF and gas reservoirs.

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arXiv2026

Far-infrared observations of dust in Ly$\alpha$ emitters at z=2-6

The bright Ly$\alpha$ line is regularly used to identify high-redshift star-forming galaxies known as Ly$\alpha$ emitters (LAEs). However, Ly$\alpha$ is affected by resonant scattering and dust absorption making interpretation of its brightness challenging without additional observations. We use SCUBA-2, PACS and SPIRE data to investigate the far-infrared emission, Ly$\alpha$ escape fraction ($f{esc}$(Ly$\alpha$)) and infrared excess (IRX=LIR/LUV) in $\sim$4000 LAEs at z=2.2-6 from SC4K. Five LAEs, all hosting AGN, are individually detected with fluxes $S_{850}$ = 3.7-5.5 mJy at 850$\mu\mathrm{m}$. Stacking is used to probe the average emission from all individually undetected LAEs, though the stacks are undetected at all wavelengths (e.g. $S_{850}$ < 0.09 mJy; 3$\sigma$). We group the sample into bins of redshift, stellar mass, Ly$\alpha$ luminosity and AGN status. Most subsets are undetected but LAEs containing AGN and that have high stellar masses ($M_{\star} = 10^{10} - 10^{12}\, M_{\odot}$; including and excluding AGN) are detected at most wavelengths, suggesting that stellar mass and AGN heating may be enhancing the dust visibility. Individually detected LAEs and detected stacks have $f{esc}$(Ly$\alpha$)=1-7%, while all undetected stacks $\geq$ 10%. All LAEs together average over > 21% and display significant scatter, suggesting a clumpy ISM dust distribution. Non-zero $f{esc}$(Ly$\alpha$) in massive and AGN-hosting LAEs suggests ionizing photons may escape even from dusty galaxies, challenging the idea that dusty galaxies are poor leakers. Examination of the IRX-$\beta_{UV}$ relation shows LAEs have higher IRX than typical star-forming galaxies at similar redshifts. However, our detections tend to favour more massive, AGN-hosting systems and deeper observations are therefore needed.

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arXiv2025

J-HERTz: J-PLUS Heritage Exploration of Radio Targets at z $<$ 5

We introduce J-HERTz (J-PLUS Heritage Exploration of Radio Targets at $z < 5$), a new multi-wavelength catalog that combines optical narrow-band photometry from J-PLUS, infrared observations from WISE, and deep low-frequency radio data from LoTSS for nearly half a million sources across 2,100 deg$^2$ of the northern sky. Key innovations of J-HERTz include Bayesian neural network classifications for 390,000 galaxies, 31,000 quasars, and 20,000 stars, along with significantly improved photometric redshifts for 235,000 galaxies compared to previous J-PLUS DR3 and LoTSS DR2 estimates. We identify 831 candidate Galactic radio stars, which, if confirmed, would constitute a significant addition to the number of radio-emitting stars identified to date. Among radio-loud galaxies with spectroscopic observations, $\gtrsim$20% lack Seyfert or LINER signatures, indicating a substantial population of optically quiescent radio galaxies, in agreement with previous works. Spectral energy distribution fitting of their host galaxies using J-PLUS photospectra reveals systematically low specific star formation rates, consistent with quenched stellar populations. J-HERTz thus provides a powerful dataset to exploit radio-optical synergies, enabling studies that span from the origin of stellar radio emission to the AGN life cycle and the role of jet activity in shaping host galaxy evolution.

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arXiv2025

Rapid, out of equilibrium metal enrichment indicated by a flat mass-metallicity relation at z~6 from NIRCam grism spectroscopy

We aim to characterise the mass-metallicity relation (MZR) and the 3D correlation between stellar mass, metallicity and star-formation rate (SFR) known as the fundamental metallicity relation (FMR) for galaxies at $5<z<7$. Using $\sim800$ [O III] selected galaxies from deep NIRCam grism surveys, we present our stacked measurements of direct-$T\rm_e$ metallicities, which we use to test recent strong-line metallicity calibrations. Our measured direct-$T\rm_e$ metallicities ($0.1$-$0.2\,\rm Z_\odot$ for M$_\star$ $\approx5\times10^{7-9}$ M$_{\odot}$, respectively) match recent JWST/NIRSpec-based results. However, there are significant inconsistencies between observations and hydrodynamical simulations. We observe a flatter MZR slope than the SPHINX$^{20}$ and FLARES simulations, which cannot be attributed to selection effects. With simple models, we show that the effect of an [O III] flux-limited sample on the observed shape of the MZR is strongly dependent on the FMR. If the FMR is similar to the one in the local Universe, the intrinsic high-redshift MZR should be even flatter than observed. In turn, a 3D relation where SFR correlates positively with metallicity at fixed mass would imply an intrinsically steeper MZR. Our measurements indicate that metallicity variations at fixed mass show little dependence on the SFR, suggesting a flat intrinsic MZR. This could indicate that the low-mass galaxies at these redshifts are out of equilibrium and that metal enrichment occurs rapidly in low-mass galaxies. However, being limited by our stacking analysis, we are yet to probe the scatter in the MZR and its dependence on SFR. Large carefully selected samples of galaxies with robust metallicity measurements can put tight constraints on the high-redshift FMR and, help to understand the interplay between gas flows, star formation and feedback in early galaxies.

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arXiv2025

A "Black Hole Star" Reveals the Remarkable Gas-Enshrouded Hearts of the Little Red Dots

The physical processes that led to the formation of billion solar mass black holes within the first 700 million years of cosmic time remain a puzzle. Several theoretical scenarios have been proposed to seed and rapidly grow black holes, but direct observations of these mechanisms remain elusive. Here we present a source 660 million years after the Big Bang that displays singular properties: among the largest Hydrogen Balmer breaks reported at any redshift, broad multi-peaked H$\beta$ emission, and Balmer line absorption in multiple transitions. We model this source as a "black hole star" (BH*) where the Balmer break and absorption features are a result of extremely dense, turbulent gas forming a dust-free "atmosphere" around a supermassive black hole. This source may provide evidence of an early black hole embedded in dense gas -- a theoretical configuration proposed to rapidly grow black holes via super-Eddington accretion. Radiation from the BH* appears to dominate almost all observed light, leaving limited room for contribution from its host galaxy. We demonstrate that the recently discovered "Little Red Dots" (LRDs) with perplexing spectral energy distributions can be explained as BH*s embedded in relatively brighter host galaxies. This source provides evidence that black hole masses in the LRDs may be over-estimated by orders of magnitude -- the BH* is effectively dust-free contrary to the steep dust corrections applied while modeling LRDs, and the physics that gives rise to the complex line shapes and luminosities may deviate from assumptions underlying standard scaling relations.

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arXiv2025

J-PLUS: Spectroscopic validation of H$\alpha$ emission line maps in spatially resolved galaxies

We present a dedicated automated pipeline to construct spatially resolved emission H$\alpha$+[NII] maps and to derive the spectral energy distributions (SEDs) in 12 optical filters (five broad and seven narrow/medium) of H$\alpha$ emission line regions in nearby galaxies (z $<$ 0.0165) observed by the Javalambre Photometric Local Universe Survey (J-PLUS). We used the $J0660$ filter of $140${\AA} width centered at $6600${\AA} to trace H$\alpha$ + [NII] emission and $r$ and $i$ broad bands were used to estimate the stellar continuum. We create pure emission line images after the continnum subtraction, where the H$\alpha$ emission line regions were detected. This method was also applied to Integral Field Unit (IFU) spectroscopic data from PHANGS-MUSE, CALIFA and MaNGA surveys by building synthetic narrow-bands based on J-PLUS filters. The studied sample includes the cross-matched catalog of these IFU surveys with J-PLUS third data release (DR3), amounting to $2$ PHANGS-MUSE, $78$ CALIFA, and $78$ MaNGA galaxies at $z < 0.0165$, respectively. We compared the H$\alpha$+[NII] radial profiles from J-PLUS and the IFU surveys, finding good agreement within the expected uncertainties. We also compared the SEDs from the emission line regions detected in J-PLUS images, reproducing the main spectral features present in the spectroscopic data. Finally, we compared the emission fluxes from the J-PLUS and IFU surveys accounting for scale differences, finding a difference of only 2% with a dispersion of 7% in the measurements. The J-PLUS data provides reliable spatially resolved H$\alpha$+[NII] emission maps for nearby galaxies. We provide the J-PLUS DR3 catalog for the $158$ galaxies with IFU data, including emission maps, SEDs of star-forming clumps, and radial profiles.

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arXiv2024

An unambiguous AGN and a Balmer break in an Ultraluminous Little Red Dot at z=4.47 from Ultradeep UNCOVER and All the Little Things Spectroscopy

We present a detailed exploration of the most optically-luminous Little Red Dot ($L_{H\alpha}=10^{44}$erg/s, $L_V=10^{45}$erg/s, F444W=22AB) found to date. Located in the Abell 2744 field, source A744-45924 was observed by NIRSpec/PRISM with ultradeep spectroscopy reaching SNR$\sim$100pix$^{-1}$, high-resolution 3-4 micron NIRCam/Grism spectroscopy, and NIRCam Medium Band imaging. The NIRCam spectra reveal high rest-frame EW $W_{H\alpha,0,broad}>800$\r{A}, broad H$\alpha$ emission (FWHM$\sim$4500 km/s), on top of narrow, complex absorption. NIRSpec data show exceptionally strong rest-frame UV to NIR Fe II emission ($W_{FeII-UV,0}\sim$340\r{A}), N IV]$\lambda\lambda$1483,1486 and N III]$\lambda$1750, and broad NIR O I $\lambda$8446 emission. The spectra unambiguously demonstrate a broad-line region associated with an inferred $M_{BH}\sim10^9M_\odot$ supermassive black hole embedded in dense gas, which might explain a non-detection in ultradeep Chandra X-ray data (>$10\times$ underluminous relative to broad $L_{H\alpha}$). Strong UV Nitrogen lines suggest supersolar N/O ratios due to rapid star formation or intense radiation near the AGN. The continuum shows a clear Balmer break at rest-frame 3650\r{A}, which cannot be accounted for by an AGN power-law alone. A stellar population model produces an excellent fit with a reddened Balmer break and implying a massive ($M_*\sim8\times10^{10}M_\odot$), old $\sim$500 Myr, compact stellar core, among the densest stellar systems known ($\rho\sim3\times10^6M_\odot$/pc$^2$ for $R_{e,opt}=70\pm10$ pc), and AGN emission with extreme intrinsic EW $W_{H\alpha,0}\gg$1000\r{A}. However, although high $M_*$ and $M_{BH}$ are supported by evidence of an overdensity containing 40 galaxies at $z=4.41-4.51$, deep high-resolution spectroscopy is required to confirm stellar absorption and rule out that dense gas around the AGN causes the Balmer break instead.

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arXiv2024

All the Little Things in Abell 2744: $>$1000 Gravitationally Lensed Dwarf Galaxies at $z=0-9$ from JWST NIRCam Grism Spectroscopy

Dwarf galaxies hold the key to crucial frontiers of astrophysics, however, their faintness renders spectroscopy challenging. Here we present the JWST Cycle 2 survey, All the Little Things (ALT, PID 3516), which is designed to seek late-forming Pop III stars and the drivers of reionization at $z\sim6-7$. ALT has acquired the deepest NIRCam grism spectroscopy yet (7-27 hr), at JWST's most sensitive wavelengths (3-4 $\mu$m), covering the powerful lensing cluster Abell 2744. Over the same 30 arcmin$^2$, ALT's ultra-deep F070W+F090W imaging ($\sim$30 mag) enables selection of very faint sources at $z>6$. We demonstrate the success of ALT's novel ``butterfly" mosaic to solve spectral confusion and contamination, and introduce the ``Allegro" method for emission line identification. By collecting spectra for every source in the field of view, ALT has measured precise ($R\sim1600$) redshifts for 1630 sources at $z=0.2-8.5$. This includes one of the largest samples of distant dwarf galaxies: [1015, 475, 50] sources less massive than the SMC, Fornax, and Sculptor with $\log(M_{*}/M_{\odot})<$[8.5, 7.5, 6.5]. We showcase ALT's discovery space with: (i) spatially resolved spectra of lensed clumps in galaxies as faint as $M_{\rm{UV}}\sim-15$; (ii) large-scale clustering -- overdensities at $z$=[2.50, 2.58, 3.97, 4.30, 5.66, 5.77, 6.33] hosting massive galaxies with striking Balmer breaks; (iii) small-scale clustering -- a system of satellites around a Milky Way analog at $z\sim6$; (iv) spectroscopically confirmed multiple images that help constrain the lensing model underlying all science in this legacy field; (v) sensitive star-formation maps based on dust-insensitive tracers such as Pa$\alpha$; (vi) direct spectroscopic discovery of rare sources such as AGN with ionized outflows. These results provide a powerful proof of concept for how grism surveys maximize the potential of strong lensing fields.

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arXiv2024

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: an unbiased study of SMG environments measured with narrowband imaging

Submillimetre galaxies (SMGs) are some of the most extreme star-forming systems in the Universe, whose place in the framework of galaxy evolution is as yet uncertain. It has been hypothesised that SMGs are progenitors of local early-type galaxies, requiring that SMGs generally reside in galaxy cluster progenitors at high redshift. We test this hypothesis and explore SMG environments using a narrowband VLT/HAWK-I+GRAAL study of H$\alpha$ and [OIII] emitters around an unbiased sample of three ALMA-identified and spectroscopically-confirmed SMGs at $z \sim 2.3$ and $z \sim 3.3$, where these SMGs were selected solely on spectroscopic redshift. Comparing with blank-field observations at similar epochs, we find that one of the three SMGs lies in an overdensity of emission-line sources on the $\sim4$ Mpc scale of the HAWK-I field of view, with overdensity parameter $\delta_{g} = 2.6^{+1.4}_{-1.2}$. A second SMG is significantly overdense only on $\lesssim 1.6$ Mpc scales and the final SMG is consistent with residing in a blank field environment. The total masses of the two overdensities are estimated to be $\log(M_{h}/{\rm M}_{\odot}) =$12.1--14.4, leading to present-day masses of $\log(M_{h,z=0}/{\rm M}_{\odot}) =$12.9--15.9. These results imply that SMGs occupy a range of environments, from overdense protoclusters or protogroups to the blank field, suggesting that while some SMGs are strong candidates for the progenitors of massive elliptical galaxies in clusters, this may not be their only possible evolutionary pathway.

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arXiv2024

Evolution of H$\alpha$ Equivalent Widths from $z \sim 0.4-2.2$: implications for star formation and legacy surveys with Roman and Euclid

We investigate the `intrinsic' H$\alpha$ EW distributions of $z \sim 0.4 - 2.2$ narrowband-selected H$\alpha$ samples from HiZELS and DAWN using a forward modeling approach. We find an EW - stellar mass anti-correlation with steepening slopes $-0.18\pm0.03$ to $-0.24^{+0.06}_{-0.08}$ at $z \sim 0.4$ and $z\sim 2.2$, respectively. Typical EW increases as $(1+z)^{1.78^{+0.22}_{-0.23}}$ for a $10^{10}$ M$_\odot$ emitter from $15^{+2.4}_{-2.3}$\r{A} ($z \sim 0.4$) to $67.7^{+10.4}_{-10.0}$\r{A} ($z \sim 2.2$) and is steeper with decreasing stellar mass highlighting the high EW nature of low-mass high-$z$ systems. We model this redshift evolving anti-correlation, $W_0(M,z)$, and find it produces H$\alpha$ luminosity and SFR functions strongly consistent with observations validating the model and allowing us to use $W_0(M,z)$ to investigate the relative contribution of H$\alpha$ emitters towards cosmic SF. We find EW$_0 > 200$ \r{A} emitters contribute significantly to cosmic SF activity at $z \sim 1.5 - 2$ making up $\sim 40$% of total SF consistent with sSFR $> 10^{-8.5}$ yr$^{-1}$ ($\sim 45 - 55$%). Overall, this highlights the importance of high EW systems at high-$z$. Our $W_0(M,z)$ model also reproduces the cosmic sSFR evolution found in simulations and observations and show that tension between the two can simply arise from selection effects in observations. Lastly, we forecast Roman and Euclid grism surveys using $W_0(M,z)$ including observational efficiency and limiting resolution effects where we predict $\sim 24000$ and $\sim 30000$ $0.5 < z < 1.9$ H$\alpha$ emitters per deg$^{-2}$, respectively, down to $>5\times10^{-17}$ erg s$^{-1}$ cm$^{-2}$ including $10^{7.2 - 8}$ M$_\odot$ galaxies at $z > 1$ with EW$_0 >1000$\r{A}. Both Roman and Euclid will enable us to observe with unprecedented detail some of the most bursty/high EW, low-mass star-forming galaxies near cosmic noon.

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arXiv2024

Anatomy of an ionized bubble: NIRCam grism spectroscopy of the $z=6.6$ double-peaked Lyman-$\alpha$ emitter COLA1 and its environment

The increasingly neutral intergalactic gas at $z>6$ impacts the Lyman-$\alpha$ flux observed from galaxies. One luminous galaxy, COLA1, stands out because of its unique double-peaked Ly$\alpha$ line at $z=6.6$, unseen in any simulation of reionization. Here we present JWST/NIRCam wide-field slitless spectroscopy in a 21 arcmin$^2$ field centered on COLA1. We find 141 galaxies spectroscopically-selected through the [OIII]($\lambda4969,5008$) doublet at $5.35 M_{\rm UV}>-19.5$).

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arXiv2022

The Velocity Dispersion Function for Massive Quiescent and Star-Forming Galaxies at 0.6 $<$ z $\leq$ 1.0

We present the first direct spectroscopic measurement of the stellar velocity dispersion function (VDF) for massive quiescent and star-forming galaxies at $0.6 < z \leq 1.0$. For this analysis we use individual measurements of stellar velocity dispersion from high-S/N spectra from the public Large Early Galaxy Astrophysics Census (LEGA-C) survey. We report a remarkable stability of the VDF for both quiescent and star-forming galaxies within this redshift range, though we note the presence of weak evolution in the number densities of star-forming galaxies. We compare both VDFs with previous direct and inferred measurements at local and intermediate redshifts, with the caveat that previous measurements of the VDF for star-forming galaxies are poorly constrained at all epochs. We emphasize that this work is the first to directly push to low-stellar velocity dispersion ($\sigma_\star > 100$ km s$^{-1}$) and extend to star-forming galaxies. We are largely consistent with the high-sigma tail measured from BOSS, and we find that the VDF remains constant from the median redshift of LEGA-C, $z\sim0.8$, to the present day.

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arXiv2022

Signs of environmental effects on star-forming galaxies in the Spiderweb protocluster at z=2.16

We use multi-object near-infrared (NIR) spectroscopy with VLT/KMOS to investigate the role of the environment in the evolution of the ionized gas properties of narrow-band selected H$\alpha$ emitters (HAEs) in the Spiderweb protocluster at $z=2.16$. Based on rest-frame optical emission lines, H$\alpha$ and [NII]$\lambda$6584, we confirm the cluster membership of 39 of our targets (i.e. 93% success rate), and measure their star-formation rates (SFR), gas-phase oxygen abundances and effective radius. We parametrize the environment where our targets reside by using local and global density indicators based on previous samples of spectroscopic and narrow-band cluster members. We find that star-forming galaxies embedded in the Spiderweb protocluster display SFRs compatible with those of the main sequence and morphologies comparable to those of late-type galaxies at $z=2.2$ in the field. We also report a mild gas-phase metallicity enhancement ($0.6\pm0.3$ dex) at intermediate stellar masses. Furthermore, we identify two UVJ-selected quiescent galaxies with residual H$\alpha$-based star formation and find signs of extreme dust obscuration in a small sample of SMGs based on their FIR and H$\alpha$ emission. Interestingly, the spatial distribution of these objects differs from the rest of HAEs, avoiding the protocluster core. Finally, we explore the gas fraction-gas metallicity diagram for 7 galaxies with molecular gas masses measured by ATCA using CO(1-0). In the context of the gas-regulator model, our objects are consistent with relatively low mass-loading factors, suggesting lower outflow activity than field samples at the cosmic noon and thus, hinting at the onset of environmental effects in this massive protocluster.

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arXiv2022

The Mass Scale of High-Redshift Galaxies: Virial Mass Estimates Calibrated with Stellar Dynamical Models from LEGA-C

Dynamical models for $673$ galaxies at $z=0.6-1.0$ with spatially resolved (long-slit) stellar kinematic data from LEGA-C are used to calibrate virial mass estimates defined as $M_{\rm{vir}}=K \sigma'^2_{\star,\rm{int}} R$, with $K$ a scaling factor, $\sigma'_{\star,\rm{int}}$ the spatially-integrated stellar velocity second moment from the LEGA-C survey and $R$ the effective radius measured from a S\'ersic profile fit to HST imaging. The sample is representative for $M_{\star}>3\times10^{10}~M_{\odot}$ and includes all types of galaxies, irrespective of morphology and color. We demonstrate that using $R=R_{\rm{sma}}$~(the semi-major axis length of the ellipse that encloses 50\% of the light) in combination with an inclination correction on $\sigma'_{\star,\rm{int}}$~produces an unbiased $M_{\rm{vir}}$. We confirm the importance of projection effects on $\sigma'_{\star,\rm{int}}$ by showing the existence of a similar residual trend between virial mass estimates and inclination for the nearby early-type galaxies in the ATLAS$^{\rm{3D}}$~survey. Also, as previously shown, when using a S\'ersic profile-based $R$ estimate, then a S\'{e}rsic index-dependent correction to account for non-homology in the radial profiles is required. With respect to analogous dynamical models for low-redshift galaxies from the ATLAS$^{\rm{3D}}$~survey we find a systematic offset of 0.1 dex in the calibrated virial constant for LEGA-C, which may be due to physical differences between the galaxy samples or an unknown systematic error. Either way, with our work we establish a common mass scale for galaxies across 8 Gyr of cosmic time with a systematic uncertainty of at most 0.1 dex.

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arXiv2022

The miniJPAS survey: Identification and characterization of the emission line galaxies down to $z < 0.35$ in the AEGIS field

The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) is expected to map thousands of square degrees of the northern sky with 56 narrowband filters in the upcoming years. This will make J-PAS a very competitive and unbiased emission line survey compared to spectroscopic or narrowband surveys with fewer filters. The miniJPAS survey covered 1 deg$^2$, and it used the same photometric system as J-PAS, but the observations were carried out with the pathfinder J-PAS camera. In this work, we identify and characterize the sample of emission line galaxies (ELGs) from miniJPAS with a redshift lower than $0.35$. Using a method based on artificial neural networks, we detect the ELG population and measure the equivalent width and flux of the $H\alpha$, $H\beta$, [OIII], and [NII] emission lines. We explore the ionization mechanism using the diagrams [OIII]/H$\beta$ versus [NII]/H$\alpha$ (BPT) and EW(H$\alpha$) versus [NII]/H$\alpha$ (WHAN). We identify 1787 ELGs ($83$%) from the parent sample (2154 galaxies) in the AEGIS field. For the galaxies with reliable EW values that can be placed in the WHAN diagram (2000 galaxies in total), we obtained that $72.8 \pm 0.4$%, $17.7 \pm 0.4$% , and $9.4 \pm 0.2$% are star-forming (SF), active galactic nucleus (Seyfert), and quiescent galaxies, respectively. Based on the flux of $H\alpha$ we find that the star formation main sequence is described as $\log$ SFR $[M_\mathrm{\odot} \mathrm{yr}^{-1}] = 0.90^{+ 0.02}_{-0.02} \log M_{\star} [M_\mathrm{\odot}] -8.85^{+ 0.19}_{-0.20}$ and has an intrinsic scatter of $0.20^{+ 0.01}_{-0.01}$. The cosmic evolution of the SFR density ($\rho_{\text{SFR}}$) is derived at three redshift bins: $0 < z \leq 0.15$, $0.15 < z \leq 0.25$, and $0.25 < z \leq 0.35$, which agrees with previous results that were based on measurements of the $H\alpha$ emission line.

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arXiv2022

LEGA-C: analysis of dynamical masses from ionized gas and stellar kinematics at z~0.8

We compare dynamical mass estimates based on spatially extended stellar and ionized gas kinematics ($\mathrm{M_{dyn,*}}$ and $\mathrm{M_{dyn,eml}}$, respectively) of 157 star forming galaxies at $0.6\leq z<1$. Compared to $z\sim0$, these galaxies have enhanced star formation rates, with stellar feedback likely affecting the dynamics of the gas. We use LEGA-C DR3, the highest redshift dataset providing sufficiently deep measurements of a $K_s-$band limited sample. For $\mathrm{M_{dyn,*}}$ we use Jeans Anisotropic Multi-Gaussian Expansion models. For $\mathrm{M_{dyn,eml}}$ we first fit a custom model of a rotating exponential disk with uniform dispersion, whose light is projected through a slit and corrected for beam smearing. We then apply an asymmetric drift correction based on assumptions common in the literature to the fitted kinematic components to obtain the circular velocity, assuming hydrostatic equilibrium. Within the half-light radius, $\mathrm{M_{dyn,eml}}$ is on average lower than $\mathrm{M_{dyn,*}}$, with a mean offset of $-0.15\pm0.016$ dex and galaxy-to-galaxy scatter of $0.19$ dex, reflecting the combined random uncertainty. While data of higher spatial resolution are needed to understand this small offset, it supports the assumption that the galaxy-wide ionized gas kinematics do not predominantly originate from disruptive events such as star formation driven outflows. However, a similar agreement can be obtained without modeling from the integrated emission line dispersions for axis ratios $q<0.8$. This suggests that our current understanding of gas kinematics is not sufficient to efficiently apply asymmetric drift corrections to improve dynamical mass estimates compared to observations lacking the $S/N$ required for spatially extended dynamics.

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arXiv2021

The LEGA-C of nature and nurture in stellar populations of galaxies at z~0.6-1.0: D4000 and H-delta reveal different assembly histories for quiescent galaxies in different environments

Galaxy evolution is driven by a variety of physical processes which are predicted to proceed at different rates for different dark matter haloes and environments across cosmic times. A record of this evolution is preserved in galaxy stellar populations, which we can access using absorption-line spectroscopy. Here we explore the large LEGA-C survey (DR3) to investigate the role of the environment and stellar mass on stellar populations at z~0.6-1.0 in the COSMOS field. Leveraging the statistical power and depth of LEGA-C, we reveal significant gradients in D4000 and H-delta equivalent widths (EWs) distributions over the stellar mass vs environment 2D spaces for the massive galaxy population (M>10^10 M$_{\odot}$) at z~0.6-1.0. D4000 and H-delta EWs primarily depend on stellar mass, but they also depend on environment at fixed stellar mass. By splitting the sample into centrals and satellites, and in terms of star-forming galaxies and quiescent galaxies, we reveal that the significant environmental trends of D4000 and H-delta EW when controlling for stellar mass are driven by quiescent galaxies. Regardless of being centrals or satellites, star-forming galaxies reveal D4000 and H-delta EWs which depend strongly on their stellar mass and are completely independent of the environment at 0.6<z<1.0. The environmental trends seen for satellite galaxies are fully driven by the trends that hold only for quiescent galaxies, combined with the strong environmental dependency of the quiescent fraction at fixed stellar mass. Our results are consistent with recent predictions from simulations that point towards massive galaxies forming first in over-densities or the most compact dark matter haloes.

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arXiv2021

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

Precise measurements of black hole masses are essential to understanding the coevolution of these sources and their host galaxies. We develop a novel approach for computing black hole virial masses using measurements of continuum luminosities and emission line widths from partially overlapping, narrow-band observations of quasars; we refer to this technique as single-epoch photometry. This novel method relies on forward-modelling quasar observations for estimating emission line widths, which enables unbiased measurements even for lines coarsely resolved by narrow-band data. We assess the performance of this technique using quasars from the Sloan Digital Sky Survey (SDSS) observed by the miniJPAS survey, a proof-of-concept project of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS) collaboration covering $\simeq1\,\mathrm{deg}^2$ of the northern sky using the 56 J-PAS narrow-band filters. We find remarkable agreement between black hole masses from single-epoch SDSS spectra and single-epoch miniJPAS photometry, with no systematic difference between these and a scatter ranging from 0.4 to 0.07 dex for masses from $\log(M_\mathrm{BH})\simeq8$ to 9.75, respectively. Reverberation mapping studies show that single-epoch masses present approximately 0.4 dex precision, letting us conclude that our novel technique delivers black hole masses with only mildly lower precision than single-epoch spectroscopy. The J-PAS survey will soon start observing thousands of square degrees without any source preselection other than the photometric depth in the detection band, and thus single-epoch photometry has the potential to provide details on the physical properties of quasar populations that do not satisfy the preselection criteria of previous spectroscopic surveys.

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