arXiv subjects

P. Arrabal Haro

Publications and source records attributed to P. Arrabal Haro.

25 records · Page 2Linked to original sources

arXiv2023

Delving deep: a population of extremely dusty dwarfs observed by JWST

We take advantage of the NIRCam photometric observations available as part of the Cosmic Evolution Early Release Science survey (CEERS) to identify and analyse very red sources in an effort to discover very dusty star forming galaxies. We select red galaxies as objects with a S/N>3 at 4.4 $μ$m and a S/N<2 in all JWST and HST filters at $λ\leq2μ$m, which corresponds to [F200W]-[F444W]>1.2 considering CEERS depths. This selection is ideal to identify very dusty (Av>1 mag) galaxies with stellar masses between $10^6$ to $10^{10}\, \rm M_{\odot}$ at z<5, more massive dusty galaxies at z=5-18 and galaxies at z>18 due to the Lyman absorption, independently of their dust extinction. Our sample of F200W-dropouts contains no strong candidates at z>6.5, instead it consists almost completely (~81%) of z<2 low-mass galaxies, with a median stellar mass of $10^{7.3} \rm M_{\odot}$. These galaxies show an exceptional dust extinction with median value of Av=4.9 mag, completely unexpected given their low stellar mass. The remaining galaxies, which are at z<6.5, show similar large dust extinction (Av>1), but they are generally more massive $>10^{7.5}\rm M_{\odot}$.

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arXiv2023

CEERS Key Paper VI: JWST/MIRI Uncovers a Large Population of Obscured AGN at High Redshifts

Mid-infrared observations are powerful in identifying heavily obscured Active Galactic Nuclei (AGN) which have weak emission in other wavelengths. Data from the Mid-Infrared Instrument (MIRI) onboard JWST provides an excellent opportunity to perform such studies. We take advantage of the MIRI imaging data from the Cosmic Evolution Early Release Science Survey (CEERS) to investigate the AGN population in the distant universe. We estimate the source properties of MIRI-selected objects by utilizing spectral energy distribution (SED) modelling, and classify them into star-forming galaxies (SF), SF-AGN mixed objects, and AGN. The source numbers of these types are 418, 111, and 31, respectively, from 4 MIRI pointings covering $\sim 9$ arcmin$^2$. The sample spans a redshift range of $\approx 0$--5. We derive the median SEDs for all three source types, respectively, and publicly release them. The median MIRI SED of AGN is similar to the typical SEDs of hot dust-obscured galaxies and Seyfert 2s, for which the mid-IR SEDs are dominantly from AGN-heated hot dust. Based on our SED-fit results, we estimate the black-hole accretion density (BHAD; i.e., total BH growth rate per comoving volume) as a function of redshift. At $z<3$, the resulting BHAD agrees with the X-ray measurements in general. At $z>3$, we identify a total of 27 AGN and SF-AGN mixed objects, leading to that our high-$z$ BHAD is substantially higher than the X-ray results ($\sim 0.5$ dex at $z \approx 3$--5). This difference indicates MIRI can identify a large population of heavily obscured AGN missed by X-ray surveys at high redshifts.

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arXiv2023

Galaxy Morphology from $z\sim6$ through the eyes of JWST

We analyze the Near Infrared ($\sim0.8-1μ$m) rest-frame morphologies of galaxies with $\log M_*/M_\odot>9$ in the redshift range $0 10.5$) at $z\sim5$, and bulge-dominated galaxies also exist at these early epochs, confirming a rich and evolved morphological diversity of galaxies $\sim1$ Gyr after the Big Bang. Finally, we find that the morphology-quenching relation is already in place for massive galaxies at $z>3$, with massive quiescent galaxies ($\log M_*/M_\odot>10.5$) being predominantly bulge-dominated.

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arXiv2021

Probing the existence of a rich galaxy overdensity at z=5.2

We report the results of a pilot spectroscopic program of a region at z=5.2 in the GOODS-N field containing an overdensity of galaxies around the well-known submillimeter galaxy HDF850.1. We have selected candidate cluster members from the optical 25 medium-band photometric catalog of the project SHARDS (Survey for High-z Absorption Red and Dead Sources). 17 rest-frame UV selected galaxies (LAEs and LBGs) with 5.15 10^15 M_sun).

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arXiv2020

Differences and similarities of stellar populations in LAEs and LBGs at $z\sim$ 3.4 - 6.8

The differences between the inherent stellar populations (SPs) of LAEs and LBGs are a key factor in understanding early galaxy formation and evolution. We have run a set of SP burst-like models for a sample of 1,558 sources at $3.4<z<6.8$ from the Survey for High-$z$ Absorption Red and Dead Sources (SHARDS) over the GOODS-N field. This work focuses on the differences between the three different observational subfamilies of our sample: LAE-LBGs, no-Ly$α$ LBGs and pure LAEs. Single and double SP synthetic spectra were used to model the SEDs, adopting a Bayesian information criterion to analyse under which situations a second SP is required. We find that the sources are well modelled using a single SP in $\sim79\%$ of the cases. The best models suggest that pure LAEs are typically young low mass galaxies ($t\sim26^{+41}_{-25}$ Myr; $M_{\mathrm{star}}\sim5.6^{+12.0}_{-5.5}\times10^{8}\ M_{\odot}$), undergoing one of their first bursts of star formation. On the other hand, no-Ly$α$ LBGs require older SPs ($t\sim71\pm12$ Myr), and they are substantially more massive ($M_{\mathrm{star}}\sim3.5\pm1.1\times10^{9}\ M_{\odot}$). LAE-LBGs appear as the subgroup that more frequently needs the addition of a second SP, representing an old and massive galaxy caught in a strong recent star-forming episode. The relative number of sources found from each subfamily at each $z$ supports an evolutionary scenario from pure LAEs and single SP LAE-LBGs to more massive LBGs. Stellar Mass Functions are also derived, finding an increase of $M^{*}$ with cosmic time and a possible steepening of the low mass slope from $z\sim6$ to $z\sim5$ with no significant change to $z\sim4$. Additionally, we have derived the SFR-$M_{\mathrm{star}}$ relation, finding a $\mathrm{SFR}\propto M_{\mathrm{star}}^β$ behaviour with negligible evolution from $z\sim4$ to $z\sim6$.

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arXiv2018

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

We have undertaken a comprehensive search for both Lyman Alpha Emitters (LAEs) and Lyman Break Galaxies (LBGs) in the SHARDS Survey of the GOODS-N field. SHARDS is a deep imaging survey, made with the 10.4 m Gran Telescopio Canarias (GTC), employing 25 medium band filters in the range from 500 to 941 nm. This is the first time that both LAEs and LBGs are surveyed simultaneously in a systematic way in a large field. We draw a sample of 1558 sources; 528 of them are LAEs. Most of the sources (1434) show rest-frame UV continua. A minority of them (124) are pure LAEs with virtually no continuum detected in SHARDS. We study these sources from $z\sim3.35$ up to $z\sim6.8$, well into the epoch of reionization. Note that surveys done with just one or two narrow band filters lack the possibility to spot the rest-frame UV continuum present in most of our LAEs. We derive redshifts, Star Formation Rates (SFRs), Ly$α$ Equivalent Widths (EWs) and Luminosity Functions (LFs). Grouping within our sample is also studied, finding 92 pairs or small groups of galaxies at the same redshift separated by less than 60 comoving kpc. In addition, we relate 87 and 55 UV-selected objects with two known overdensities at $z=4.05$ and $z=5.198$, respectively. Finally, we show that surveys made with broad band filters are prone to introduce many unwanted sources ($\sim20$% interlopers), which means that previous studies may be overestimating the calculated LFs, specially at the faint end.

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arXiv2018

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

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. In this work, 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. We use data from the SHARDS multiband survey in the GOODS-North field. Its depth (up to magnitude $\langle m_{3σ}\rangle\sim26.5$) and its spectro-photometric resolution ($R\sim50$) 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. We find 160 star-forming galaxies with equivalent widths (EWs) as low as 12 Å, with median values for the sample of $\sim$ 35 Å in [OIII]5007 and $\sim$ 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 ($A_V \sim$ 0.37), with median galaxy stellar mass $\sim$ 10$^{8.5}$ M$_{\odot}$. Gas-phase metallicities measured from available spectra are also low. ELGs in our sample present bluer colors in the UVJ plane than the median color-selected star-forming galaxy in SHARDS. We suggest a new (V-J) color criterion to separate ELGs from non-ELGs in blue galaxy samples. In addition, several galaxies present high densities of O-type stars. 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.

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