Examinando por Autor "Ibar, Eduardo"
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Ítem ALMA reveals the molecular gas properties of 5 star-forming galaxies across the main sequence at 3 < z < 3:5.(European Southern Observatory, 2020) Ibar, EduardoWe present the detection of CO (5−4) with signal-to-noise ratio (S/N) > 7–13 and a lower CO transition with S/N > 3 (CO (4−3) for four galaxies, and CO (3−2) for one) with the Atacama Large Millimeter/submillimeter Array in bands 3 and 4 in five main-sequence (MS) star-forming galaxies with stellar masses (3–6) × 1010M⊙ at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity LFIR and the luminosity of the CO (5−4) transition ${L}_{\mathrm{CO}(5-4)}^{{\prime} }$, where ${L}_{\mathrm{CO}(5-4)}^{{\prime} }$ increases with star formation rate (SFR), indicating that CO (5−4) is a good tracer of the obscured SFR in these galaxies. The two galaxies that lie closer to the star-forming MS have CO spectral line energy distribution (SLED) slopes that are comparable to other star-forming populations, such as local submillimeter galaxies and BzK star-forming galaxies; the three objects with higher specific star formation rates have far steeper CO SLEDs, which possibly indicates a more concentrated episode of star formation. By exploiting the CO SLED slopes to extrapolate the luminosity of the CO (1−0) transition and using a classical conversion factor for MS galaxies of ${\alpha }_{\mathrm{CO}}=3.8\,{M}_{\odot}{({\rm{K}}\mathrm{km}{{\rm{s}}}^{-1}{\mathrm{pc}}^{-2})}^{-1}$, we find that these galaxies are very gas-rich, with molecular gas fractions between 60% and 80% and quite long depletion times, between 0.2 and 1 Gyr. Finally, we obtain dynamical masses that are comparable to the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the αCO parameter for MS galaxies at an unprecedented redshift.Ítem The ALPINE-ALMA [C II] Survey: [C II] 158micron Emission Line Luminosity Functions at z∼4−6(American Astronomical Society, 2020) Ibar, EduardoWe present the [C II] 158 μm line luminosity functions (LFs) at z ~ 4–6 using the ALMA observations of 118 sources, which are selected to have UV luminosity M1500Å < −20.2 and optical spectroscopic redshifts in COSMOS and ECDF-S. Of the 118 targets, 75 have significant [C II] detections and 43 are upper limits. This is by far the largest sample of [C II] detections, which allows us to set constraints on the volume density of [C II] emitters at z ~ 4–6. But because this is a UV-selected sample, we are missing [C II]-bright but UV-faint sources, making our constraints strict lower limits. Our derived LFs are statistically consistent with the z ~ 0 [C II] LF at 108.25–109.75L⊙. We compare our results with the upper limits of the [C II] LF derived from serendipitous sources in the ALPINE maps. We also infer the [C II] LFs based on published far-IR and CO LFs at z ~ 4–6. Combining our robust lower limits with these additional estimates, we set further constraints on the true number density of [C II] emitters at z ~ 4–6. These additional LF estimates are largely above our LF at L[CII] > 109L⊙, suggesting that UV-faint but [C II]-bright sources likely make significant contributions to the [C II] emitter volume density. When we include all the LF estimates, we find that available model predictions underestimate the number densities of [C II] emitters at z ~ 4–6. Finally, we set a constraint on the molecular gas mass density at z ~ 4–6, with ρmol ~ (2–7) × 107M⊙ Mpc−3. This is broadly consistent with previous studies.Ítem The ALPINE-ALMA [C II] survey: Molecular gas budget in the Early Universe as traced by [C II](European Southern Observatory, 2020) Ibar, EduardoThe molecular gas content of normal galaxies at z > 4 is poorly constrained because the commonly used molecular gas tracers become hard to detect at these high redshifts. We use the [C II] 158 μm luminosity, which was recently proposed as a molecular gas tracer, to estimate the molecular gas content in a large sample of main sequence star-forming galaxies at z = 4.4 − 5.9, with a median stellar mass of 109.7 M⊙, drawn from the ALMA Large Program to INvestigate [C II] at Early times survey. The agreement between the molecular gas masses derived from [C II] luminosities, dynamical masses, and rest-frame 850 μm luminosities extrapolated from the rest-frame 158 μm continuum supports [C II] as a reliable tracer of molecular gas in our sample. We find a continuous decline of the molecular gas depletion timescale from z = 0 to z = 5.9, which reaches a mean value of (4.6 ± 0.8) × 108 yr at z ∼ 5.5, only a factor of between two and three shorter than in present-day galaxies. This suggests a mild enhancement of the star formation efficiency toward high redshifts. Our estimates also show that the previously reported rise in the molecular gas fraction flattens off above z ∼ 3.7 to achieve a mean value of 63%±3% over z = 4.4 − 5.9. This redshift evolution of the gas fraction is in line with that of the specific star formation rate. We use multi-epoch abundance-matching to follow the gas fraction evolution across cosmic time of progenitors of z = 0 Milky Way-like galaxies in ∼1013 M⊙ halos and of more massive z = 0 galaxies in ∼1014 M⊙ halos. Interestingly, the former progenitors show a monotonic increase of the gas fraction with redshift, while the latter show a steep rise from z = 0 to z ∼ 2 followed by a constant gas fraction from z ∼ 2 to z = 5.9. We discuss three possible effects, namely outflows, a pause in gas supply, and over-efficient star formation, which may jointly contribute to the gas fraction plateau of the latter massive galaxies.Ítem The ALPINE-ALMA [CII] Survey: A Triple Merger at z ~ 4.56(Royal Astronomical Society, 2020) Ibar, EduardoWe report the detection of [C II] λ158 μm emission from a system of three closely separated sources in the Cosmic Evolution Survey (COSMOS) field at z ∼ 4.56 , as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program to INvestigate C II at Early times (ALPINE). The two most luminous sources are closely associated, both spatially (1.6 arcsec ∼ 11 kpc) and in velocity (∼100 km s−1), while the third source is slightly more distant (2.8 arcsec ∼ 18 kpc, ∼300 km s−1). The second most luminous source features a slight velocity gradient, while no significant velocity gradient is seen in the other two sources. Using the observed [C II] luminosities, we derive a total log10(SFR[CII][M⊙yr−1])=2.8±0.2, which may be split into contributions of 59, 31, and 10 per cent from the central, east, and west sources, respectively. Comparison of these [C II] detections to recent zoom-in cosmological simulations suggests an ongoing major merger. We are thus witnessing a system in a major phase of mass build-up by merging, including an ongoing major merger and an upcoming minor merger, which is expected to end up in a single massive galaxy by z ∼ 2.5.Ítem The ALPINE-ALMA [CII] survey: Data processing, catalogs, and statistical source properties(European Southern Observatory, 2020) Ibar, EduardoThe Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE) targets the [CII] 158 m line and the far-infrared continuum in 118 spectroscopically confirmed star-forming galaxies between z=4.4 and z=5.9. It represents the first large [CII] statistical sample built in this redshift range.We present details regarding the data processing and the construction of the catalogs.We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates (SFRs), we measured the conversion factor from the ALMA 158 m rest-frame dust continuum luminosity to the total infrared luminosity (LIR) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data.We found that our continuum detections have a median LIR of 4.4 1011 L .We also detected 57 additional continuum sources in our ALMA pointings. They are at a lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5 0.2.We measured the 850 m number counts between 0.35 and 3.5 mJy, thus improving the current interferometric constraints in this flux density range.We found a slope break in the number counts around 3 mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35 mJy. Finally, we detected the [CII] line in 75 of our targets. Their median [CII] luminosity is 4.8 108 L and their median full width at half maximum is 252 km/s. After measuring the mean obscured SFR in various [CII] luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR-L[CII] relations. The ALPINE products are publicly available at https://cesam.lam.fr/a2c2s/.Ítem The ALPINE-ALMA [CII] survey: Dust attenuation properties and obscured star formation at z ~ 4:4 - 5:8(European Southern Observatory, 2020) Ibar, EduardoWe present dust attenuation properties of spectroscopically confirmed star forming galaxies on the main sequence at a redshift of ∼4.4 − 5.8. Our analyses are based on the far infrared continuum observations of 118 galaxies at rest-frame 158 μm obtained with the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE). We study the connection between the ultraviolet (UV) spectral slope (β), stellar mass (M⋆), and infrared excess (IRX = LIR/LUV). Twenty-three galaxies are individually detected in the continuum at > 3.5σ significance. We perform a stacking analysis using both detections and nondetections to study the average dust attenuation properties at z ∼ 4.4 − 5.8. The individual detections and stacks show that the IRX–β relation at z ∼ 5 is consistent with a steeper dust attenuation curve than typically found at lower redshifts (z < 4). The attenuation curve is similar to or even steeper than that of the extinction curve of the Small Magellanic Cloud. This systematic change of the IRX–β relation as a function of redshift suggests an evolution of dust attenuation properties at z > 4. Similarly, we find that our galaxies have lower IRX values, up to 1 dex on average, at a fixed mass compared to previously studied IRX–M⋆ relations at z ≲ 4, albeit with significant scatter. This implies a lower obscured fraction of star formation than at lower redshifts. Our results suggest that dust properties of UV-selected star forming galaxies at z ≳ 4 are characterised by (i) a steeper attenuation curve than at z ≲ 4, and (ii) a rapidly decreasing dust obscured fraction of star formation as a function of redshift. Nevertheless, even among this UV-selected sample, massive galaxies (log M⋆/M⊙ > 10) at z ∼ 5 − 6 already exhibit an obscured fraction of star formation of ∼45%, indicating a rapid build-up of dust during the epoch of reionization.Ítem The ALPINE-ALMA [CII] survey: Little to no evolution in the [CII]–SFR relation over the last 13 Gyr(European Southern Observatory, 2020) Ibar, Eduardo; Mendez Hernandez, HugoThe [C ii] 158 m line is one of the strongest IR emission lines, which has been shown to trace the star formation rate (SFR) of galaxies in the nearby Universe, and up to z 2. Whether this is also the case at higher redshift and in the early Universe remains debated. The ALPINE survey, which targeted 118 star-forming galaxies at 4:4 < z < 5:9, provides a new opportunity to examine this question with the first statistical dataset. Using the ALPINE data and earlier measurements from the literature, we examine the relation between the [C ii] luminosity and the SFR over the entire redshift range from z 4 ����� 8. ALPINE galaxies, which are both detected in [C ii] and in dust continuum, show good agreement with the local L([CII])–SFR relation. Galaxies undetected in the continuum by ALMA are found to be over-luminous in [C ii]when the UV SFR is used. After accounting for dust-obscured star formation, by an amount of SFR(IR) SFR(UV) on average, which results from two di erent stacking methods and SED fitting, the ALPINE galaxies show an L([CII])–SFR relation comparable to the local one. When [C ii] non-detections are taken into account, the slope may be marginally steeper at high-z, although this is still somewhat uncertain. When compared homogeneously, the z > 6 [C ii] measurements (detections and upper limits) do not behave very di erently to the z 4 ����� 6 data.We find a weak dependence of L([CII])/SFR on the Ly equivalent width. Finally, we find that the ratio L([CII])/LIR (1 ����� 3) 10�����3 for the ALPINE sources, comparable to that of ‘normal’ galaxies at lower redshift. Our analysis, which includes the largest sample ( 150 galaxies) of [C ii] measurements at z > 4 available so far, suggests no or little evolution of the [C ii]–SFR relation over the last 13 Gyr of cosmic time.Ítem The ALPINE-ALMA [CII] Survey: On the nature of an extremely obscured serendipitous galaxy(Royal Astronomical Society, 2020) Ibar, EduardoWe report the serendipitous discovery of a dust-obscured galaxy observed as part of the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE). While this galaxy is detected both in line and continuum emissions in ALMA Band 7, it is completely dark in the observed optical/near-infrared bands and only shows a significant detection in the UltraVISTA Ks band. We discuss the nature of the observed ALMA line, that is [C II] at z ∼ 4.6 or high-J CO transitions at z ∼ 2.2. In the first case, we find a [CII]/FIR luminosity ratio of log(L[CII]/LFIR) ∼ −2.5, consistent with the average value for local star-forming galaxies (SFGs). In the second case instead, the source would lie at larger CO luminosities than those expected for local SFGs and high-z submillimetre galaxies. At both redshifts, we derive the star formation rate (SFR) from the ALMA continuum and the physical parameters of the galaxy, such as the stellar mass (M∗), by fitting its spectral energy distribution. Exploiting the results of this work, we believe that our source is a ‘main-sequence’, dusty SFG at z = 4.6 (i.e. [CII] emitter) with log(SFR/M. yr−1) ~ 1.4 and log(M*/M.) ∼ 9.9. As a support to this scenario our galaxy, if at this redshift, lies in a massive protocluster recently discovered at z ∼ 4.57, at only ∼1 proper Mpc from its centre. This work underlines the crucial role of the ALPINE survey in making a census of this class of objects, in order to unveil their contribution to the global SFR density at the end of the Reionization epochÍtem The ALPINE-ALMA [CII] survey: Small Lya-[CII] velocity offsets in main-sequence galaxies at 4.4 < z < 6(European Southern Observatory, 2020) Ibar, Eduardo; Mendez Hernandez, HugoContext. The Lyman- line in the ultraviolet (UV) and the [CII] line in the far-infrared (FIR) are widely used tools to identify galaxies in the early Universe and to obtain insights into interstellar medium (ISM) properties in high-redshift galaxies. By combining data obtained with ALMA in band 7 at 320 GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at the Keck Observatory, VIMOS and FORS2 at the Very Large Telescope, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4:4 < z < 6 in which we detect both the Lyman- line in the UV and the [CII] line in the FIR. Aims. The goal of this paper is to constrain the properties of the Ly emission in these galaxies in relation to other properties of the ISM. Methods. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we exploited the available optical spectroscopy to obtain the Ly -[CII] and ISM-[CII] velocity offsets. Results. We find that 90% of the selected objects have Ly -[CII] velocity offsets in the range 0 < vLy �����[CII] < 400 km s�����1, in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower redshifts. At the same time, we observe ISM-[CII] offsets in the range �����500 < vISM�����[CII] < 0 km s�����1, in line with values at all redshifts, which we interpret as evidence for outflows in these galaxies. We find significant anticorrelations between vLy �����[CII] and the Ly rest-frame equivalent width EW0(Ly ) (or equivalently, the Ly escape fraction fesc(Ly )): galaxies that show smaller vLy �����[CII] have larger EW0(Ly ) and fesc(Ly ). Conclusions. We interpret these results in the framework of available models for the radiative transfer of Ly photons. According to the models, the escape of Ly photons would be favored in galaxies with high outflow velocities, producing large EW0(Ly ) and small vLy �����[CII], in agreement with our observations. The uniform shell model would also predict that the Ly escape in galaxies with slow outflows (0 < vout < 300 km s�����1) is mainly determined by the neutral hydrogen column density (NHI) along the line of sight, while the alternative model by Steidel et al. (2010) would more highly favor a combination of NHI at the systemic velocity and covering fraction as driver of the Ly escape. We suggest that the observed increase in Ly escape that is observed in the literature between z 2 and z 6 is not due to a higher incidence of fast outflows at high redshift, but rather to a decrease in average NHI along the line of sight, or alternatively, a decrease in HI covering fractionÍtem The ALPINE-ALMA [CII] survey: Star-formation-driven outflows and circumgalactic enrichment in the early Universe(The European Southern Observatory (ESO), 2020) Ibar, EduardoWe study the efficiency of galactic feedback in the early Universe by stacking the [C II] 158 µm emission in a large sample of normal star-forming galaxies at 4 < z < 6 from the ALMA Large Program to INvestigate [C II] at Early times (ALPINE) survey. Searching for typical signatures of outflows in the high-velocity tails of the stacked [C II] profile, we observe (i) deviations from a single-component Gaussian model in the combined residuals and (ii) broad emission in the stacked [C II] spectrum, with velocities of |v| . 500 km s−1 The significance of these features increases when stacking the subset of galaxies with star formation rates (SFRs) higher than the median (SFRmed = 25 M yr−1 ), thus confirming their star-formation-driven nature. The estimated mass outflow rates are comparable to the SFRs, yielding mass-loading factors of the order of unity (similarly to local star-forming galaxies), suggesting that star-formation-driven feedback may play a lesser role in quenching galaxies at z > 4. From the stacking analysis of the datacubes, we find that the combined [C II] core emission (|v| < 200 km s−1) of the higher-SFR galaxies is extended on physical sizes of ∼ 30 kpc (diameter scale), well beyond the analogous [C II] core emission of lower-SFR galaxies and the stacked far-infrared continuum. The detection of such extended metal-enriched gas, likely tracing circumgalactic gas enriched by past outflows, corroborates previous similar studies, confirming that baryon cycle and gas exchanges with the circumgalactic medium are at work in normal star-forming galaxies already at early epochsÍtem The ALPINE-ALMA [CII] survey: Survey strategy, observations, and sample properties of 118 star-forming galaxies at 4(European Southern Observatory, 2020) Ibar, Eduardo; Mendez Hernandez, HugoThe ALMA-ALPINE [CII] survey is aimed at characterizing the properties of a sample of normal star-forming galaxies (SFGs). The ALMA Large Program to INvestigate (ALPINE) features 118 galaxies observed in the [CII]-158μm line and far infrared (FIR) continuum emission during the period of rapid mass assembly, right after the end of the HI reionization, at redshifts of 45). Based on a visual inspection of the [CII] data cubes together with the large wealth of ancillary data, we find a surprisingly wide range of galaxy types, including 40% that are mergers, 20% extended and dispersion-dominated, 13% compact, and 11% rotating discs, with the remaining 16% too faint to be classified. This diversity indicates that a wide array of physical processes must be at work at this epoch, first and foremost, those of galaxy mergers. This paper sets a reference sample for the gas distribution in normal SFGs at 4Ítem The ALPINE–ALMA [CII] Survey: Multiwavelength Ancillary Data and Basic Physical Measurements(The American Astronomical Society, 2020) Ibar, EduardoWe present the ancillary data and basic physical measurements for the galaxies in the ALMA Large Program to Investigate C+ at Early Times (ALPINE) survey—the first large multiwavelength survey that aims at characterizing the gas and dust properties of 118 main-sequence galaxies at redshifts 4.4 < z < 5.9 via the measurement of [${\rm{C}}\,{\rm{II}}$] emission at $158\,\mu {\rm{m}}$ (64% at >3.5σ) and the surrounding far-infrared continuum in conjunction with a wealth of optical and near-infrared data. We outline in detail the spectroscopic data and selection of the galaxies as well as the ground- and space-based imaging products. In addition, we provide several basic measurements including stellar masses, star formation rates (SFR), rest-frame ultra-violet (UV) luminosities, UV continuum slopes (β), and absorption line redshifts, as well as Hα emission derived from Spitzer colors. We find that the ALPINE sample is representative of the 4 < z < 6 galaxy population selected by photometric methods and only slightly biased toward bluer colors (Δβ ~ 0.2). Using [${\rm{C}}\,{\rm{II}}$] as tracer of the systemic redshift (confirmed for one galaxy at z = 4.5 out of 118 for which we obtained optical [${\rm{O}}\,{\rm{III}}$]λ3727Å emission), we confirm redshifted Lyα emission and blueshifted absorption lines similar to findings at lower redshifts. By stacking the rest-frame UV spectra in the [${\rm{C}}\,{\rm{II}}$] rest frame, we find that the absorption lines in galaxies with high specific SFR are more blueshifted, which could be indicative of stronger winds and outflows.Ítem The ALPINE–ALMA [CII] Survey: Size of Individual Star-forming Galaxies at z = 4–6 and Their Extended Halo Structure(American Astronomical Society, 2020) Ibar, Eduardo; Mendez Hernandez, HugoWe present the physical extent of [C ii] 158 μm line-emitting gas from 46 star-forming galaxies at z = 4–6 from the ALMA Large Program to INvestigate C ii at Early Times (ALPINE). Using exponential profile fits, we measure the effective radius of the [C ii] line (${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}$) for individual galaxies and compare them with the rest-frame ultraviolet (UV) continuum (${r}_{{\rm{e}},\mathrm{UV}}$) from Hubble Space Telescope images. The effective radius ${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}$ exceeds ${r}_{{\rm{e}},\mathrm{UV}}$ by factors of ~2–3, and the ratio of ${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}/{r}_{{\rm{e}},\mathrm{UV}}$ increases as a function of Mstar. We do not find strong evidence that the [C ii] line, rest-frame UV, and far-infrared (FIR) continuum are always displaced over sime1 kpc scale from each other. We identify 30% of isolated ALPINE sources as having an extended [C ii] component over 10 kpc scales detected at 4.1σ–10.9σ beyond the size of rest-frame UV and FIR continuum. One object has tentative rotating features up to ~10 kpc, where the 3D model fit shows the rotating [C ii]-gas disk spread over 4 times larger than the rest-frame UV-emitting region. Galaxies with the extended [C ii] line structure have high star formation rate, high stellar mass (Mstar), low Lyα equivalent width, and more blueshifted (redshifted) rest-frame UV metal absorption (Lyα line), as compared to galaxies without such extended [C ii] structures. Although we cannot rule out the possibility that a selection bias toward luminous objects may be responsible for such trends, the star-formation-driven outflow also explains all these trends. Deeper observations are essential to test whether the extended [C ii] line structures are ubiquitous to high-z star-forming galaxies.Ítem The atomic gas of star-forming galaxies at z~0.05 as revealed by the Five-hundred-meter Aperture Spherical Radio Telescope(European Southern Observatory, 2020) Ibar, Eduardo; Hughes, ThomasContext. We report new Hi observations of four z ∼ 0.05 VALES galaxies undertaken during the commissioning phase of the Fivehundred-meter Aperture Spherical Radio Telescope (FAST). Aims. FAST is the largest single-dish telescope in the world, with a 500 meter aperture and a 19-Beam receiver. Exploiting theunprecedented sensitivity provided by FAST, we aim to study the atomic gas content, via the Hi 21 cm emission line, in low-z star formation galaxies taken from the Valparaíso ALMA/APEX Line Emission Survey (VALES). Together with previous Atacama Large Millimeter/submillimeter Array (ALMA) CO(J = 1 − 0) observations, the Hi data provides crucial information to measure the gas mass and dynamics. Methods. As a pilot Hi galaxy survey, we targeted four local star-forming galaxies at z ∼ 0.05. In particular, one of them has already been detected in Hi by the Arecibo Legacy Fast ALFA survey (ALFALFA), allowing a careful comparison. We use an ON-OFF observing approach that allowed us to reach an rms of 0.7mJy beam−1 at a 1.7 kms−1 velocity resolution within only 20 minutes ON-target integration time. Results. In this letter, we demonstrate the great capabilities of the FAST 19-beam receiver for pushing the detectability of the Hi emission line of extra-galactic sources. The Hi emission line detected by FAST shows good consistency with the previous Arecibo telescope ALFALFA results. Our observations are put in context with previous multi-wavelength data to reveal the physical properties of these low-z galaxies. We find that the CO(J = 1 − 0) and Hi emission line profiles are similar. The dynamical mass estimated from the Hi data is an order of magnitude higher than the baryon mass and the dynamical mass derived from the CO observations, implying that the mass probed by dynamics of Hi is dominated by the dark matter halo. In one case, a target shows an excess of CO(J = 1−0) in the line centre, which can be explained by an enhanced CO(J = 1 − 0) emission induced by a nuclear starburst showing high velocity dispersion.Ítem Cosmic evolution of molecular gas mass density from an empirical relationship between L1.4 GHz and L′CO(Royal Astronomical Society, 2020) Orellana Gonzalez, Gustavo; Ibar, Eduardo; Hughes, ThomasHistorically, GHz radio emission has been used extensively to characterize the star-formation activity in galaxies. In this work, we look for empirical relationships amongst the radio luminosity, the infrared luminosity, and the CO-based molecular gas mass. We assemble a sample of 278 nearby galaxies with measurements of radio continuum and total infrared emission, and the 12CO J = 1–0 emission line. We find a correlation between the radio continuum and the CO emission line (with a scatter of 0.36 dex), in a large sample of different kinds of galaxies. Making use of this correlation, we explore the evolution of the molecular gas mass function and the cosmological molecular gas mass density in six redshift bins up to z = 1.5. These results agree with previous semi-analytic predictions and direct measurements: the cosmic molecular gas density increases up to z = 1.5. In addition, we find a single plane across five orders of magnitude for the explored luminosities, with a scatter of 0.27 dex. These correlations are sufficiently robust to be used for samples where no CO measurements exist.Ítem The e-MERGE Survey (e-MERLIN Galaxy Evolution Survey): overview and survey description(Royal Astronomical Society, 2020) Ibar, EduardoWe present an overview and description of the e-MERGE Survey (e-MERLIN Galaxy Evolution Survey) Data Release 1 (DR1), a large program of high-resolution 1.5-GHz radio observations of the GOODS-N field comprising ∼140 h of observations with enhanced-Multi-Element Remotely Linked Interferometer Network (e-MERLIN) and ∼40 h with the Very Large Array (VLA). We combine the long baselines of e-MERLIN (providing high angular resolution) with the relatively closely packed antennas of the VLA (providing excellent surface brightness sensitivity) to produce a deep 1.5-GHz radio survey with the sensitivity (∼1.5 μ Jy beam−1), angular resolution (0.2–0.7 arcsec) and field-of-view (∼15 × 15 arcmin2) to detect and spatially resolve star-forming galaxies and active galactic nucleus (AGN) at z 1. The goal of e-MERGE is to provide new constraints on the deep, sub-arcsecond radio sky which will be surveyed by SKA1-mid. In this initial publication, we discuss our data analysis techniques, including steps taken to model in-beam source variability over an ∼20-yr baseline and the development of new point spread function/primary beam models to seamlessly merge e-MERLIN and VLA data in the uv plane. We present early science results, including measurements of the luminosities and/or linear sizes of ∼500 galaxies selected at 1.5 GHz. In combination with deep Hubble Space Telescope observations, we measure a mean radio-to-optical size ratio of re-MERGE/rHST ∼ 1.02 ± 0.03, suggesting that in most high-redshift galaxies, the ∼GHz continuum emission traces the stellar light seen in optical imaging. This is the first in a series of papers that will explore the ∼kpc-scale radio properties of star-forming galaxies and AGN in the GOODS-N field observed by e-MERGE DR1.Ítem From Peculiar Morphologies to Hubble–type Spirals: The relation between galaxy dynamics and morphology in star–forming galaxies at z ∼ 1.5(Royal Astronomical Society, 2020) Ibar, EduardoWe present an analysis of the gas dynamics of star-forming galaxies at z ∼ 1.5 using data from the KMOS Galaxy Evolution Survey. We quantify the morphology of the galaxies using HSTCANDELS imaging parametrically and non-parametrically. We combine the H α dynamics from KMOS with the high-resolution imaging to derive the relation between stellar mass (M*) and stellar specific angular momentum (j*). We show that high-redshift star-forming galaxies at z ∼ 1.5 follow a power-law trend in specific stellar angular momentum with stellar mass similar to that of local late-type galaxies of the form j* ∝ M0.53±0.10∗. The highest specific angular momentum galaxies are mostly disc-like, although generally both peculiar morphologies and disc-like systems are found across the sequence of specific angular momentum at a fixed stellar mass. We explore the scatter within the j* – M* plane and its correlation with both the integrated dynamical properties of a galaxy (e.g. velocity dispersion, Toomre Qg, H α star formation rate surface density ΣSFR) and its parametrized rest-frame UV / optical morphology (e.g. Sérsic index, bulge to total ratio, clumpiness, asymmetry, and concentration). We establish that the position in the j* – M* plane is strongly correlated with the star-formation surface density and the clumpiness of the stellar light distribution. Galaxies with peculiar rest-frame UV / optical morphologies have comparable specific angular momentum to disc- dominated galaxies of the same stellar mass, but are clumpier and have higher star formation rate surface densities. We propose that the peculiar morphologies in high-redshift systems are driven by higher star formation rate surface densities and higher gas fractions leading to a more clumpy interstellar medium.Ítem A kpc-scale resolved study of unobscured and obscured star-formation activity in normal galaxies at z = 1.5 and 2.2 from ALMA and HiZELS(Royal Astronomical Society, 2020) Cheng, Cheng; Ibar, Eduardo; Hughes, ThomasWe present Atacama Large Millimeter/Submillimeter Array (ALMA) continuum observations of a sample of nine star-forming galaxies at redshifts 1.47 and 2.23 selected from the High-z Emission Line Survey (HiZELS). Four galaxies in our sample are detected at high significance by ALMA at a resolution of 0′′.25 at rest-frame 355 μm. Together with the previously observed H α emission, from adaptive optics-assisted integral-field-unit spectroscopy (∼0′′.15 resolution), and F606W and F140W imaging from the Hubble Space Telescope (∼0′′.2 resolution), we study the star formation activity, stellar and dust mass in these high-redshift galaxies at ∼kpc-scale resolution. We find that ALMA detection rates are higher for more massive galaxies (M* > 1010.5 M⊙) and higher [N II]/H α ratios (>0.25, a proxy for gas-phase metallicity). The dust extends out to a radius of 8 kpc, with a smooth structure, even for those galaxies presenting clumpy H α morphologies. The half-light radii (Rdust) derived for the detected galaxies are of the order ∼4.5 kpc, more than twice the size of submillimetre-selected galaxies at a similar redshift. Our global star formation rate estimates – from far-infrared and extinction-corrected H α luminosities – are in good agreement. However, the different morphologies of the different phases of the interstellar medium suggest complex extinction properties of the high-redshift normal galaxies.Ítem Metal-THINGS: On the metallicity and ionization of ULX sources in NGC 925(American Astronomical Society, 2021) Lara-López, Maritza A.; Zinchenko, Igor A.; Pilyugin, Leonid S.; Gunawardhana, Madusha L. P.; López-Cruz, Omar; O'Sullivan, Shane P.; Feltre, Anna; Rosado, Margarita; Sánchez-Cruces, Mónica; Chevallard, Jacopo; De Rossi, Maria Emilia; Dib, Sami; Fritz, Jacopo; Fuentes-Carrera, Isaura; Garduño, Luis E.; Ibar, EduardoWe present an analysis of the optical properties of three Ultra Luminous X-ray (ULX) sources identified in NGC 925. We use Integral field unit data from the George Mitchel spectrograph in the context of the Metal-THINGS survey. The optical properties for ULX-1 and ULX-3 are presented, while the spaxel associated with ULX-2 had a low S/N, which prevented its analysis. We also report the kinematics and dimensions of the optical nebula associated with each ULX using ancillary data from the PUMA Fabry–Perot spectrograph. A BPT analysis demonstrates that most spaxels in NGC 925 are dominated by star-forming regions, including those associated with ULX-1 and ULX-3. Using the resolved gas-phase metallicities, a negative metallicity gradient is found, consistent with previous results for spiral galaxies, while the ionization parameter tends to increase radially throughout the galaxy. Interestingly, ULX-1 shows a very low gas metallicity for its galactocentric distance, identified by two independent methods, while exhibiting a typical ionization. We find that such low gas metallicity is best explained in the context of the high-mass X-ray binary population, where the low-metallicity environment favors active Roche lobe overflows that can drive much higher accretion rates. An alternative scenario invoking accretion of a low-mass galaxy is not supported by the data in this region. Finally, ULX-3 shows both a high metallicity and ionization parameter, which is consistent with the progenitor being a highly accreting neutron star within an evolved stellar population region.Ítem SCUBA-2 overdensities associated with candidate protoclusters selected from Planck data(Royal Astronomical Society, 2020) Ibar, EduardoWe measure the 850-μm source densities of 46 candidate protoclusters selected from the Planck High-z catalogue (PHz) and the Planck Catalogue of Compact Sources (PCCS) that were followed up with Herschel -SPIRE and SCUBA-2. This paper aims to search for overdensities of 850-μm sources in order to select the fields that are most likely to be genuine protoclusters. Of the 46 candidate protoclusters, 25 have significant overdensities (>5 times the field counts), 11 have intermediate overdensities (3–5 times the field counts) and 10 have no overdensity (<3 times the field counts) of 850-μm sources. We find that the enhanced number densities are unlikely to be the result of sample variance. Compared with the number counts of another sample selected from Planck’s compact source catalogues, this [PHz+PCCS]-selected sample has a higher fraction of candidate protoclusters with significant overdensities, though both samples show overdensities of 850-μm sources above intermediate level. Based on the estimated star-formation rate densities (SFRDs), we suggest that both samples can efficiently select protoclusters with starbursting galaxies near the redshift at which the global field SFRD peaks (2 < z < 3). Based on the confirmation of overdensities found here, future follow-up observations on other PHz targets may greatly increase the number of genuine DSFG-rich clusters/protoclusters.