ORCID Profile
0000-0003-1641-6185
Current Organisation
The University of Edinburgh
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Publisher: Oxford University Press (OUP)
Date: 04-12-2020
Abstract: The North Ecliptic Pole field is a natural deep-field location for many satellite observations. It has been targeted many times since it was surveyed by the AKARI space telescope with its unique wavelength coverage from the near- to mid-infrared (mid-IR). Many follow-up observations have been carried out, making this field one of the most frequently observed areas with a variety of facilities, accumulating abundant panchromatic data from the X-ray to the radio wavelength range. Recently, a deep optical survey with the Hyper Suprime-Cam (HSC) at the Subaru telescope covered the NEP-Wide (NEPW) field, which enabled us to identify faint sources in the near- and mid-IR bands, and to improve the photometric redshift (photo-z) estimation. In this work, we present newly identified AKARI sources by the HSC survey, along with multiband photometry for 91 861 AKARI sources observed over the NEPW field. We release a new band-merged catalogue combining various photometric data from the GALEX UV to submillimetre (sub-mm) bands (e.g. Herschel/SPIRE, JCMT/SCUBA-2). About ∼20 000 AKARI sources are newly matched to the HSC data, most of which seem to be faint galaxies in the near- to mid-infrared AKARI bands. This catalogue is motivating a variety of current research, and will be increasingly useful as recently launched (eROSITA/ART-XC) and future space missions (such as JWST, Euclid, and SPHEREx) plan to take deep observations in the NEP field.
Publisher: American Astronomical Society
Date: 06-2022
Abstract: The Reionization Era Bright Emission Line Survey (REBELS) is a cycle-7 ALMA Large Program (LP) that is identifying and performing a first characterization of many of the most luminous star-forming galaxies known in the z 6.5 universe. REBELS is providing this probe by systematically scanning 40 of the brightest UV-selected galaxies identified over a 7 deg 2 area for bright [C ii ] 158 μ m and [O iii ] 88 μ m lines and dust-continuum emission. Selection of the 40 REBELS targets was done by combining our own and other photometric selections, each of which is subject to extensive vetting using three completely independent sets of photometry and template-fitting codes. Building on the observational strategy deployed in two pilot programs, we are increasing the number of massive interstellar medium (ISM) reservoirs known at z 6.5 by ∼4–5× to . In this manuscript, we motivate the observational strategy deployed in the REBELS program and present initial results. Based on the first-year observations, 18 highly significant ≥ 7 σ [C ii ] 158 μ m lines have already been discovered, the bulk of which (13/18) also show ≥3.3 σ dust-continuum emission. These newly discovered lines more than triple the number of bright ISM-cooling lines known in the z 6.5 universe, such that the number of ALMA-derived redshifts at z 6.5 rival Ly α discoveries. An analysis of the completeness of our search results versus star formation rate (SFR) suggests an ∼79% efficiency in scanning for [C ii ] 158 μ m when the SFR UV+IR is M ⊙ yr −1 . These new LP results further demonstrate ALMA’s efficiency as a “redshift machine,” particularly in the Epoch of Reionization.
Publisher: American Astronomical Society
Date: 05-2023
Abstract: With just a month of data, JWST is already transforming our view of the universe, revealing and resolving starlight in unprecedented populations of galaxies. Although “HST-dark” galaxies have previously been detected at long wavelengths, these observations generally suffer from a lack of spatial resolution, which limits our ability to characterize their sizes and morphologies. Here we report on a first view of starlight from a subset of the HST-dark population that is bright with JWST/NIRCam (4.4 μ m 24.5 mag) and very faint or even invisible with HST ( .6 μ m). In this Letter we focus on a dramatic and unanticipated population of physically extended galaxies (≳0.″25). These 12 galaxies have photometric redshifts 2 z 6, high stellar masses M ⋆ ≳ 10 10 M ⊙ , and significant dust-attenuated star formation. Surprisingly, the galaxies have elongated projected axis ratios at 4.4 μ m, suggesting that the population is disk dominated or prolate and we hence refer to them as ultrared flattened objects. Most of the galaxies appear red at all radii, suggesting significant dust attenuation throughout. With R e (F444W) ∼ 1–2 kpc, the galaxies are similar in size to compact massive galaxies at z ∼ 2 and the cores of massive galaxies and S0s at z ∼ 0. The stellar masses, sizes, and morphologies of the s le suggest that some could be progenitors of lenticular or fast-rotating galaxies in the local universe. The existence of this population suggests that our previous censuses of the universe may have missed massive, dusty edge-on disks, in addition to dust-obscured starbursts.
Publisher: Oxford University Press (OUP)
Date: 09-11-2022
Abstract: Cosmic dust is an essential component shaping both the evolution of galaxies and their observational signatures. How quickly dust builds up in the early Universe remains an open question that requires deep observations at (sub-)millimetre wavelengths to resolve. Here, we use Atacama Large Millimeter Array observations of 45 galaxies from the Reionization Era Bright Emission Line Survey (REBELS) and its pilot programs, designed to target [C ii] and dust emission in UV-selected galaxies at z ∼ 7, to investigate the dust content of high-redshift galaxies through a stacking analysis. We find that the typical fraction of obscured star formation fobs = SFRIR/SFRUV+IR depends on stellar mass, similar to what is observed at lower redshift, and ranges from fobs ≈ 0.3 − 0.6 for galaxies with log10(M⋆/M⊙) = 9.4–10.4. We further adopt the z ∼ 7 stellar mass function from the literature to extract the obscured cosmic star formation rate density (SFRD) from the REBELS survey. Our results suggest only a modest decrease in the SFRD between 3 ≲ z ≲ 7, with dust-obscured star formation still contributing ${\\sim}30{{\\ \\rm per\\ cent}}$ at z ∼ 7. While we extensively discuss potential caveats, our analysis highlights the continued importance of dust-obscured star formation even well into the epoch of reionization.
Publisher: Oxford University Press (OUP)
Date: 17-08-2022
Abstract: We present specific star formation rates (sSFRs) for 40 ultraviolet (UV)-bright galaxies at z ∼ 7–8 observed as part of the Reionization Era Bright Emission Line Survey (REBELS) Atacama Large Millimeter/submillimeter Array (ALMA) large programme. The sSFRs are derived using improved star formation rate (SFR) calibrations and spectral energy distribution (SED)-based stellar masses, made possible by measurements of far-infrared (FIR) continuum emission and [C ii]-based spectroscopic redshifts. The median sSFR of the s le is $18_{-5}^{+7}$ Gyr−1, significantly larger than literature measurements lacking constraints in the FIR, reflecting the larger obscured SFRs derived from the dust continuum relative to that implied by the UV+optical SED. We suggest that such differences may reflect spatial variations in dust across these luminous galaxies, with the component dominating the FIR distinct from that dominating the UV. We demonstrate that the inferred stellar masses (and hence sSFRs) are strongly dependent on the assumed star formation history in reionization-era galaxies. When large sSFR galaxies (a population that is common at z & 6) are modelled with non-parametric star formation histories, the derived stellar masses can increase by an order of magnitude relative to constant star formation models, owing to the presence of a significant old stellar population that is outshined by the recent burst. The [C ii] line widths in the largest sSFR systems are often very broad, suggesting dynamical masses capable of accommodating an old stellar population suggested by non-parametric models. Regardless of these systematic uncertainties among derived parameters, we find that sSFRs increase rapidly toward higher redshifts for massive galaxies (9.6 & log (M*/M⊙) & 9.8), evolving as (1 + z)1.7 ± 0.3, broadly consistent with expectations from the evolving baryon accretion rates.
Publisher: EDP Sciences
Date: 09-2021
DOI: 10.1051/0004-6361/202140353
Abstract: Aims. We study a s le of H β emission line sources at z ∼ 0.9 to identify the star-forming galaxies s le and characterise them in terms of line luminosity, stellar mass, star formation rate, and morphology. The final aim is to obtain the H β luminosity function of the star-forming galaxies at this redshift. Methods. We used the red tunable filter of the instrument Optical System for Imaging low Resolution Integrated Spectroscopy (OSIRIS) at Gran Telescopio de Canarias to obtain the pseudo spectra of emission line sources in the OTELO field. From these pseudo spectra, we identified the objects with H β emission. As the resolution of the pseudo spectra allowed us to separate H β from [O III ], we were able to derive the H β flux without contamination from its adjacent line. Using data from the extended OTELO catalogue, we discriminated AGNs and studied the star formation rate, the stellar mass, and the morphology of the star-forming galaxies. Results. We find that our s le is located on the main sequence of star-forming galaxies. The sources are morphologically classified, mostly as disc-like galaxies (76%), and 90% of the s le are low-mass galaxies ( M * 10 10 M ⊙ ). The low-mass star-forming galaxies at z ∼ 0.9 that were detected by OTELO present similar properties as low-mass star-forming galaxies in the local universe, suggesting that these kinds of objects do not have a favorite epoch of formation and star formation enhancement from z ∼ 1 to now. Our s le of 40 H β star-forming galaxies include the faintest H β emitters detected so far. This allows us to constrain the faint end of the luminosity function for the H β line alone with a minimum luminosity of log L = 39 erg s −1 , which is a hundred times fainter than previous surveys. The dust-corrected OSIRIS Tunable Emission Line Object survey (OTELO) H β luminosity function established the faint-end slope as α = −1.36 ± 0.15. We increased the scope of the analysis to the bright end by adding ancillary data from the literature, which was not dust-corrected in this case. The obtained slope for this extended luminosity function is α = −1.43 ± 0.12.
Publisher: Oxford University Press (OUP)
Date: 21-02-2022
Abstract: We analyse FIR dust continuum measurements for 14 galaxies (redshift z ≈ 7) in the ALMA Reionization Era Bright Emission Line Survey (REBELS) Large Program to derive their physical properties. Our model uses three input data, i.e. (a) the UV spectral slope, β, (b) the observed UV continuum flux at 1500 Å, F1500, (c) the observed continuum flux at $\\approx 158\\, \\mu$m, F158, and considers Milky Way (MW) and SMC extinction curves, along with different dust geometries. We find that REBELS galaxies have 28−90.5 per cent of their star formation obscured the total (UV+IR) star formation rates are in the range $31.5 \\lt {\\rm SFR}/({\\rm M}_\\odot \\, {\\rm yr}^{-1}) \\lt 129.5$. The s le-averaged dust mass and temperature are $(1.3\\pm 1.1)\\times 10^7 \\, \\mathrm{M}_\\odot$ and 52 ± 11 K, respectively. However, in some galaxies dust is particularly abundant (REBELS-14, $M^{\\prime }_{\\rm d} \\approx 3.4 \\times 10^7 \\, \\mathrm{M}_\\odot$), or hot (REBELS-18, $T^{\\prime }_{\\rm d} \\approx 67$ K). The dust distribution is compact (& .3 kpc for 70 per cent of the galaxies). The inferred dust yield per supernova is $0.1 \\le y_{\\rm d}/\\, \\mathrm{M}_\\odot \\le 3.3$, with 70 per cent of the galaxies requiring $y_{\\rm d} \\lt 0.25 \\, \\mathrm{M}_\\odot$. Three galaxies (REBELS-12, 14, 39) require $y_{\\rm d} \\gt 1 \\, \\mathrm{M}_\\odot$, which is likely inconsistent with pure SN production, and might require dust growth via accretion of heavy elements from the interstellar medium. With the SFR predicted by the model and a MW extinction curve, REBELS galaxies detected in [C ii] nicely follow the local LCII−SFR relation, and are approximately located on the Kennicutt–Schmidt relation. The s le-averaged gas depletion time is $0.11\\, y_{\\rm P}^{-2}$ Gyr, where yP is the ratio of the gas-to-stellar distribution radius. For some systems, a solution simultaneously matching the observed (β, F1500, F158) values cannot be found. This occurs when the index Im = (F158/F1500)/(β − βint), where βint is the intrinsic UV slope, exceeds $I_m^{*}\\approx 1120$ for an MW curve. For these objects, we argue that the FIR and UV emitting regions are not co-spatial, questioning the use of the IRX–β relation.
Publisher: Oxford University Press (OUP)
Date: 09-05-2023
Abstract: We present Atacama Large Millimeter/Submillimeter Array (ALMA) [C ii] and ∼158 $\\rm \\mu m$ continuum observations of REBELS-25, a massive, morphologically complex ultra-luminous infrared galaxy (ULIRG LIR = $1.5^{+0.8}_{-0.5} \\times 10^{12}$ L⊙) at z = 7.31, spectroscopically confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA Large Programme. REBELS-25 has a significant stellar mass of $M_{*} = \\mbox{$ 8^{+4}_{-2} \\times 10^{9} $}{} ~\\mbox{M$_\\odot $}{}$. From dust-continuum and ultraviolet observations, we determine a total obscured + unobscured star formation rate of SFR $= \\mbox{$199^{+101}_{-63}$}{} ~ \\mbox{M$_\\odot $}~ \\mbox{${\\rm yr}$}^{-1}$. This is about four times the SFR estimated from an extrapolated main sequence. We also infer a [C ii]-based molecular gas mass of $M_{{\\rm H}_{2}} = \\mbox{$5.1^{+5.1}_{-2.6} \\times 10^{10}$}{} ~\\mbox{M$_\\odot $}{}$, implying a molecular gas depletion time of $t_{\\rm depl, {\\rm H}_{2}} = \\mbox{$0.3^{+0.3}_{-0.2} $}{}$ Gyr. We observe a [C ii] velocity gradient consistent with disc rotation, but given the current resolution we cannot rule out a more complex velocity structure such as a merger. The spectrum exhibits excess [C ii] emission at large positive velocities (∼500 km s−1), which we interpret as either a merging companion or an outflow. In the outflow scenario, we derive a lower limit of the mass outflow rate of 200 $\\mbox{M$_\\odot $}~ \\mbox{${\\rm yr}$}^{-1}$, which is consistent with expectations for a star-formation-driven outflow. Given its large stellar mass, SFR, and molecular gas reservoir ∼700 Myr after the big bang, we explore the future evolution of REBELS-25. Considering a simple, conservative model assuming an exponentially declining star formation history, constant star formation efficiency, and no additional gas inflow, we find that REBELS-25 has the potential to evolve into a galaxy consistent with the properties of high-mass quiescent galaxies recently observed at z ∼ 4.
Publisher: Oxford University Press (OUP)
Date: 28-06-2022
Abstract: We report 18 dust continuum detections (≥3.3σ) at ∼88 and 158 $\\mu{\\rm m}$ out of 49 ultraviolet (UV)-bright galaxies (MUV & −21.3 mag) at $z$ & 6.5, observed by the Cycle-7 Atacama Large Millimeter/submillimeter Array (ALMA) Large Program, Reionization-Era Bright Emission Line Survey (REBELS) and its pilot programs. This has more than tripled the number of dust continuum detections known at $z$ & 6.5. Out of these 18 detections, 12 are reported for the first time as part of REBELS. In addition, 15 of the dust continuum detected galaxies also show a [C ii]$_{\\rm 158\\,{\\rm \\mu m}}$ emission line, providing us with accurate redshifts. We anticipate more line emission detections from six targets (including three continuum detected targets) where observations are still ongoing. We estimate that all of the sources have an infrared (IR) luminosity (LIR) in a range of $3\\!-\\!8 \\times 10^{11}\\, {\\rm L_\\odot }$, except for one with $L_{\\rm IR} = 1.5^{+0.8}_{-0.5} \\times 10^{12}\\, \\, {\\rm L_{\\odot }}$. Their fraction of obscured star formation is significant at ${\\gtrsim} 50{{\\ \\rm per\\ cent}}$, despite being UV-selected galaxies. Some of the dust continuum detected galaxies show spatial offsets (∼0.5–1.5 arcsec) between the rest-UV and far-IR emission peaks. These separations could imply spatially decoupled phases of obscured and unobscured star formation, but a higher spatial resolution observation is required to confirm this. REBELS offers the best available statistical constraints on obscured star formation in UV-luminous galaxies at $z$ & 6.5.
Publisher: American Astronomical Society
Date: 08-2022
Abstract: We present the average [C ii ] 158 μ m emission line sizes of UV-bright star-forming galaxies at z ∼ 7. Our results are derived from a stacking analysis of [C ii ] 158 μ m emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C ii ] emission at z ∼ 7 has an effective radius r e of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≲ 6 galaxies. Additionally, we compared the average [C ii ] size with 4 z 6 galaxies observed by the ALMA Large Program to INvestigate [C ii ] at Early times (ALPINE). By analyzing [C ii ] sizes of 4 z 6 galaxies in two redshift bins, we find an average [C ii ] size of r e = 2.2 ± 0.2 kpc and r e = 2.5 ± 0.2 kpc for z ∼ 5.5 and z ∼ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C ii ] 158 μ m emitting regions at redshift between z ∼ 7 and z ∼ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.
Publisher: Springer Science and Business Media LLC
Date: 22-09-2021
DOI: 10.1038/S41586-021-03846-Z
Abstract: Over the past decades, rest-frame ultraviolet (UV) observations have provided large s les of UV luminous galaxies at redshift (z) greater than 6 (refs.
Publisher: Oxford University Press (OUP)
Date: 26-04-2023
Abstract: We present the first observational infrared luminosity function (IRLF) measurement in the Epoch of Reionization (EoR) based on a ultraviolet (UV)-selected galaxy s le with the Atacama Large Millimeter Array (ALMA) spectroscopic observations. Our analysis is based on the ALMA large program Reionization Era Bright Emission Line Survey (REBELS), which targets 42 galaxies at z = 6.4–7.7 with [C ii] 158 $\\rm{\\mu m}$ line scans. 16 sources exhibit dust detection, 15 of which are also spectroscopically confirmed through the [C ii] line. The infrared (IR) luminosities of the s le range from log LIR/L⊙ = 11.4 to 12.2. Using the UV luminosity function as a proxy to derive the effective volume for each of our target sources, we derive IRLF estimates, both for detections and for the full s le including IR luminosity upper limits. The resulting IRLFs are well reproduced by a Schechter function with the characteristic luminosity of $\\log L_{*}/\\mathrm{ L}_\\odot =11.6^{+0.2}_{-0.1}$ . Our observational results are in broad agreement with the average of predicted IRLFs from simulations at z ∼ 7. Conversely, our IRLFs lie significantly below lower redshift estimates, suggesting a rapid evolution from z ∼ 4 to z ∼ 7, into the reionization epoch. The IR obscured contribution to the cosmic star formation rate density at z ∼ 7 amounts to $\\mathrm{log(SFRD/{\\rm M}_{\\odot }\\,yr^{-1}\\,Mpc^{-3}) = -2.66^{+0.17}_{-0.14} }$ that is at least ∼10 per cent of UV-based estimates. We conclude that the presence of dust is already abundant in the EoR and discuss the possibility of unveiling larger s les of dusty galaxies with future ALMA and JWST observations.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Laia Barrufet.