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Carlos Gómez-Guijarro

Bio: Carlos Gómez-Guijarro is an academic researcher from Paris Diderot University. The author has contributed to research in topics: Galaxy & Star formation. The author has an hindex of 14, co-authored 23 publications receiving 519 citations. Previous affiliations of Carlos Gómez-Guijarro include Technical University of Denmark & University of Copenhagen.

Papers
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Journal ArticleDOI
21 Jun 2017-Nature
TL;DR: An analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which—surprisingly—turns out to be a fast-spinning, rotationally supported disk galaxy that must have formed in a disk, rather than in a merger-driven nuclear starburst.
Abstract: When the Universe was just 3 billion years old, half of the most massive galaxies had already ceased star formation, and such a galaxy has now been observed using gravitational lensing, unexpectedly turning out to be a compact, fast-spinning disk galaxy rather than a proto-bulge galaxy. When the Universe was only three billion years old, half of the most massive galaxies were already 'dead', meaning that few new stars would form in them. It is believed that these galaxies grew into the massive local elliptical galaxies seen today. Sune Toft et al. report an analysis of a galaxy that has been strongly gravitationally lensed. This means that they can observe spatial scales that are far smaller than those accessible by any other means. They find that, surprisingly, the galaxy is a fast-spinning disk and that its stars formed in situ rather than in a nuclear starburst. They conclude that the gas out of which the stars formed was accreted from outside the galaxy in cold streams of gas. At redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation1,2,3,4. It is believed that they were formed in intense nuclear starbursts and that they ultimately grew into the most massive local elliptical galaxies seen today, through mergers with minor companions5,6, but validating this picture requires higher-resolution observations of their centres than is currently possible. Magnification from gravitational lensing offers an opportunity to resolve the inner regions of galaxies7. Here we report an analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which—surprisingly—turns out to be a fast-spinning, rotationally supported disk galaxy. Its stars must have formed in a disk, rather than in a merger-driven nuclear starburst8. The galaxy was probably fed by streams of cold gas, which were able to penetrate the hot halo gas until they were cut off by shock heating from the dark matter halo9. This result confirms previous indirect indications10,11,12,13 that the first galaxies to cease star formation must have gone through major changes not just in their structure, but also in their kinematics, to evolve into present-day elliptical galaxies.

109 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported two secure (z = 3.775; 4.012) and one tentative (z ≈ 3.767) spectroscopic confirmations of massive and quiescent galaxies through K-band observations with Keck/MOSFIRE and Very Large Telescope/X-Shooter.
Abstract: We report two secure (z = 3.775; 4.012) and one tentative (z ≈ 3.767) spectroscopic confirmations of massive and quiescent galaxies through K-band observations with Keck/MOSFIRE and Very Large Telescope/X-Shooter. The stellar continuum emission, absence of strong nebular emission lines, and lack of significant far-infrared detections confirm the passive nature of these objects, disfavoring the alternative solution of low-redshift dusty star-forming interlopers. We derive stellar masses of log(M⋆/M⊙) ~ 11 and ongoing star formation rates placing these galaxies ≳ 1–2 dex below the main sequence at their redshifts. The adopted parameterization of the star formation history suggests that these sources experienced a strong (〈SFR〉 ~1200 - 3500 M⊙ yr⁻¹) and short (~50 Myr) burst of star formation, peaking ~150–500 Myr before the time of observation, all properties reminiscent of the characteristics of submillimeter galaxies (SMGs) at z > 4. We investigate this connection by comparing the comoving number densities and the properties of these two populations. We find a fair agreement only with the deepest submillimeter surveys detecting not only the most extreme starbursts but also more normal galaxies. We support these findings by further exploring the Illustris TNG cosmological simulation, retrieving populations of both fully quenched massive galaxies at z ~ 3–4 and SMGs at z ~ 4−5, with number densities and properties in agreement with the observations at z ~ 3 but in increasing tension at higher redshift. Nevertheless, as suggested by the observations, not all of the progenitors of quiescent galaxies at these redshifts shine as bright SMGs in their past, and, similarly, not all bright SMGs quench by z ~ 3, both fractions depending on the threshold assumed to define the SMGs themselves.

84 citations

Journal ArticleDOI
TL;DR: In this article, the authors report two secure and one tentative confirmations of massive and quiescent galaxies through K-band observations with Keck/MOSFIRE and VLT/X-Shooter.
Abstract: We report two secure ($z=3.775, 4.012$) and one tentative ($z\approx3.767$) spectroscopic confirmations of massive and quiescent galaxies through $K$-band observations with Keck/MOSFIRE and VLT/X-Shooter. The stellar continuum emission, the absence of strong nebular emission lines and the lack of significant far-infrared detections confirm the passive nature of these objects, disfavoring the alternative solution of low-redshift dusty star-forming interlopers. We derive stellar masses of $\mathrm{log}(M_{\star}/M_\odot)\sim11$ and ongoing star formation rates placing these galaxies $\gtrsim 1-2$ dex below the main sequence at their redshifts. The adopted parametrization of the star formation history suggests that these sources experienced a strong ($\langle \rm SFR \rangle \sim 1200-3500\,M_\odot\,\mathrm{yr}^{-1}$) and short ($\sim 50$ Myr) burst of star formation, peaking $\sim 150-500$ Myr before the time of observation, all properties reminiscent of the characteristics of sub-millimeter galaxies (SMGs) at $z>4$. We investigate this connection by comparing the comoving number densities and the properties of these two populations. We find a fair agreement only with the deepest sub-mm surveys detecting not only the most extreme starbursts, but also more normal galaxies. We support these findings by further exploring the Illustris-TNG cosmological simulation, retrieving populations of both fully quenched massive galaxies at $z\sim3-4$ and SMGs at $z\sim4-5$, with number densities and properties in agreement with the observations at $z\sim3$, but in increasing tension at higher redshift. Nevertheless, as suggested by the observations, not all the progenitors of quiescent galaxies at these redshifts shine as bright SMGs in their past and, similarly, not all bright SMGs quench by $z\sim3$, both fractions depending on the threshold assumed to define the SMGs themselves.

79 citations

Journal ArticleDOI
TL;DR: In this article, a detailed spatially resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ≥ 4.5 is presented.
Abstract: Dust-enshrouded, starbursting, submillimeter galaxies (SMGs) at z ≥ 3 have been proposed as progenitors of z ≥ 2 compact quiescent galaxies (cQGs). To test this connection, we present a detailed spatially resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ~ 4.5. The stellar UV emission probed by HST is extended and irregular and shows evidence of multiple components. Informed by HST, we deblend Spitzer/IRAC data at rest-frame optical, finding that the systems are undergoing minor mergers with a typical stellar mass ratio of 1:6.5. The FIR dust continuum emission traced by ALMA locates the bulk of star formation in extremely compact regions (median r e = 0.70 ± 0.29 kpc), and it is in all cases associated with the most massive component of the mergers (median log(M*/M⊙) = 10.49 ± 0.32). We compare spatially resolved UV slope (β) maps with the FIR dust continuum to study the infrared excess (IRX = L_(IR)/L_(UV))–β relation. The SMGs display systematically higher IRX values than expected from the nominal trend, demonstrating that the FIR and UV emissions are spatially disconnected. Finally, we show that the SMGs fall on the mass–size plane at smaller stellar masses and sizes than the cQGs at z = 2. Taking into account the expected evolution in stellar mass and size between z = 4.5 and z = 2 due to the ongoing starburst and mergers with minor companions, this is in agreement with a direct evolutionary connection between the two populations.

78 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented the first stellar velocity dispersion measurement of a massive quenching galaxy at z = 4.01, which is the most distant quiescent galaxy known to date.
Abstract: We present the first stellar velocity dispersion measurement of a massive quenching galaxy at z = 4. The galaxy is first identified as a massive z ≥ 4 galaxy with suppressed star formation from photometric redshifts based on deep multiband data. A follow-up spectroscopic observation with MOSFIRE on Keck revealed strong multiple absorption features, which are identified as Balmer lines, giving a secure redshift of z = 4.01. This is the most distant quiescent galaxy known to date. Thanks to the high S/N of the spectrum, we are able to estimate the stellar velocity dispersion, σ=268±59 km s⁻¹, making a significant leap from the previous highest redshift measurement at z = 2.8. Interestingly, we find that the velocity dispersion is consistent with that of massive galaxies today, implying no significant evolution in velocity dispersion over the last 12 Gyr. Based on a stringent upper limit on its physical size from deep optical images (r_(eff) < 1.3 kpc), we find that its dynamical mass is consistent with the stellar mass inferred from photometry. Furthermore, the galaxy is located on the mass fundamental plane extrapolated from lower redshift galaxies. The observed no strong evolution in σ suggests that the mass in the core of massive galaxies does not evolve significantly, while most of the mass growth occurs in the outskirts of the galaxies, which also increases the size. This picture is consistent with a two-phase formation scenario in which mass and size growth is due to accretion in the outskirts of galaxies via mergers. Our results imply that the first phase may be completed as early as z ~ 4.

53 citations


Cited by
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01 May 2001
TL;DR: The SWIRE project as mentioned in this paper is the largest of the SIRTF Legacy programs, which surveys 65 sq. deg. in seven high latitude fields selected to be the best wide low-extinction windows into the extragalactic sky.
Abstract: The largest of the SIRTF Legacy programs, SWIRE will survey 65 sq. deg. in seven high latitude fields selected to be the best wide low-extinction windows into the extragalactic sky. SWIRE will detect millions of spheroids, disks and starburst galaxies to z>3 and will map L* and brighter systems on scales up to 150 Mpc at z∼0.5–1. It will also detect ∼104 low extinction AGN and large numbers of obscured AGN. An extensive program of complementary observations is underway. The data are non-proprietary and will be made available beginning in Spring 2004.

484 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigate the stellar populations for a sample of 24 quiescent galaxies at 1.5 < z < 2.5 using deep rest-frame optical spectra obtained with Keck MOSFIRE.
Abstract: We investigate the stellar populations for a sample of 24 quiescent galaxies at 1.5 < z < 2.5 using deep rest-frame optical spectra obtained with Keck MOSFIRE. By fitting templates simultaneously to the spectroscopic and photometric data, and exploring a variety of star formation histories, we obtain robust measurements of median stellar ages and residual levels of star formation. After subtracting the stellar templates, the stacked spectrum reveals the Halpha and [NII] emission lines, providing an upper limit on the ongoing star formation rate of 0.9 +/- 0.1 Msun/yr. By combining the MOSFIRE data to our sample of Keck LRIS spectra at lower redshift, we analyze in a consistent manner the quiescent population at 1 < z < 2.5. We find a tight relation (with a scatter of 0.13 dex) between the stellar age and the rest-frame U-V and V-J colors, which can be used to estimate the age of quiescent galaxies given their colors. Applying this age--color relation to large, photometric samples, we are able to model the number density evolution for quiescent galaxies of various ages. We find evidence for two distinct quenching paths: a fast quenching that produces compact post-starburst systems, and a slow quenching of larger galaxies. Fast quenching accounts for about a fifth of the growth of the red sequence at z~1.4, and half at z~2.2. We conclude that fast quenching is triggered by dramatic events such as gas-rich mergers, while slow quenching is likely caused by a different physical mechanism.

136 citations

01 Jan 2009
TL;DR: In this article, the column densities of neutral atomic hydrogen (HI) and molecular hydrogen (H2) were analyzed in a sample of 245 local galaxies and a model for the column density of HI and H2 in arbitrary regular galaxies was derived.
Abstract: Neutral atomic hydrogen (HI) and molecular hydrogen (H2) play a primordial role in the cosmic evolution of galaxies. However, little is known about the co-evolution of these two gas phases. This discrepancy and the design of future telescopes like the SKA and ALMA require theoretical models of the joint evolution of HI and H2 in galaxies. This thesis starts with a phenomenological analysis of the H2/HI-ratios in a sample of 245 local galaxies. This analysis reveals a number of correlations between H2/HI-ratios and other galaxy properties, and we demonstrate that these correlations can be understood in terms of the microscopic relation between the H2/HI-ratio and the external gas pressure. We subsequently use this relation to derive an analytic model for the column densities of HI and H2 in arbitrary regular galaxies. As a second step, we apply the model for the column densities of HI and H2 to post-process approximately 3*10^7 virtual galaxies, whose cosmic evolution was simulated on the evolving dark matter skeleton output by the Millennium Simulation. The post-processing of these galaxies allows us to (i) split their total cold gas masses between HI, H2, and Helium, (ii) to assign realistic sizes to both the HI and H2-disks, and (iii) to evaluate the velocity profiles of HI and H2. The resulting hydrogen simulation successfully reproduces many local observations of HI and H2, such as mass functions (MFs), mass-diameter relations, and mass-velocity relations. A key prediction of this simulation is that the H2/HI-ratio of regular galaxies increases dramatically with redshift z, leading to a scaling of (1+z)^1.6 for the ratio between the cosmic space densities of H2 and HI. This prediction offers a unified explanation for (i) the weak evolution of the cosmic HI-density inferred from Lyman-alpha absorption against quasars, (ii) the large molecular masses detected in regular galaxies at z=1.5, and (iii) the recent cosmic decline in the density of star formation. As a third step, we introduce a heuristic model for the conversion of H2-masses into observable CO-line luminosities for galaxies at all redshifts. We apply this model to our hydrogen simulation in order to predict the luminosity functions of the first 10 rotational transitions of CO in galaxies at redshift z=0 to z=10. As a final step, we transform the simulated catalog of 3*10^7 evolving galaxies into a virtual observing cone, i.e. a catalog that lists the apparent HI and CO-line fluxes and corresponding line widths of millions of galaxies in a sky field with a comoving diameter of 500 Mpc/h. This catalog represents a tangible contribution towards the design and operation of future telescopes, such as the SKA and ALMA.

125 citations

Journal ArticleDOI
TL;DR: The main advances ALMA has helped bring about in understanding of the dust and gas properties of high-redshift (z≳1) star-forming galaxies during these first 9 years of its science operations are reviewed, and the interesting questions that may be answered by ALMA in the years to come are highlighted.
Abstract: The Atacama Large Millimetre/submillimetre Array (ALMA) is currently in the process of transforming our view of star-forming galaxies in the distant (z≳1) universe. Before ALMA, most of what we kne...

116 citations