Examinando por Autor "Mendez Hernandez, Hugo"

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    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, Hugo
    The [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.
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    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, Hugo
    Context. 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 fraction
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    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, Hugo
    The 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 4
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    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, Hugo
    We 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.
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    VALES VI: ISM enrichment in star-forming galaxies up to z ∼ 0.2 using 12CO(1–0), 13CO(1–0), and C18O(1–0) line luminosity ratios
    (Royal Astronomical Society, 2020) Mendez Hernandez, Hugo; Ibar, Eduardo
    We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations towards 27 low-redshift (0.02 < z < 0.2) star-forming galaxies taken from the Valparaíso ALMA/APEX Line Emission Survey. We perform stacking analyses of the 12CO(1–0), 13CO(1–0), and C18O(1–0) emission lines to explore the L′ [12CO(1–0)]/L′ [13CO(1–0)] [hereafter L′ (12CO)/L′ (13CO)] and L′ [13CO(1–0)]/L′ [C18O(1–0)] [hereafter L′ (13CO)/L′ (C18O)] line luminosity ratio dependence as a function of different global galaxy parameters related to the star formation activity. The sample has far-IR luminosities of 1010.1−11.9 L⊙ and stellar masses of 109.8–10.9 M⊙ corresponding to typical star-forming and starburst galaxies at these redshifts. On average, we find an L′ (12CO)/L′ (13CO) line luminosity ratio value of 16.1 ± 2.5. Galaxies with pieces of evidence of possible merging activity tend to show higher L′ (12CO)/L′ (13CO) ratios by a factor of 2, while variations of this order are also found in galaxy samples with higher star formation rates (SFRs) or star formation efficiencies (SFEs). We also find an average L′ (13CO)/L′ (C18O) line luminosity ratio of 2.5 ± 0.6, which is in good agreement with those previously reported for starburst galaxies. We find that galaxy samples with high LIR, SFR, and SFE show low L′ (13CO)/L′ (C18O) line luminosity ratios with high L′ (12CO)/L′ (13CO) line luminosity ratios, suggesting that these trends are produced by selective enrichment of massive stars in young starbursts.