198 research outputs found
Deep into the structure of the first galaxies: SERRA views
We study the formation and evolution of a sample of Lyman Break Galaxies in
the Epoch of Reionization by using high-resolution (),
cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow
the interstellar medium (ISM) thermo-chemical non-equilibrium evolution, and
perform on-the-fly radiative transfer of the interstellar radiation field
(ISRF). The simulation outputs are post-processed to compute the emission of
far infrared lines ([CII], [NII], and [OIII]). At , the most massive
galaxy, `Freesia', has an age , stellar mass
, and a star formation rate
, due to a recent burst.
Freesia has two stellar components (A and B) separated by ; other 11 galaxies are found within . The
mean ISRF in the Habing band is and is spatially uniform; in
contrast, the ionisation parameter is , and
has a patchy distribution peaked at the location of star-forming sites. The
resulting ionising escape fraction from Freesia is .
While [CII] emission is extended (radius 1.54 kpc), [OIII] is concentrated in
Freesia-A (0.85 kpc), where the ratio . As many high- galaxies, Freesia lies below the local [CII]-SFR
relation. We show that this is the general consequence of a starburst phase
(pushing the galaxy above the Kennicutt-Schmidt relation) which
disrupts/photodissociates the emitting molecular clouds around star-forming
sites. Metallicity has a sub-dominant impact on the amplitude of [CII]-SFR
deviations.Comment: 22 pages, 14 figures, accepted by MNRA
Photoevaporation of Jeans-unstable molecular clumps
We study the photoevaporation of Jeans-unstable molecular clumps by isotropic FUV (6 eV < h\u3bd < 13.6 eV) radiation, through 3D radiative transfer hydrodynamical simulations implementing a non-equilibrium chemical network that includes the formation and dissociation of H2. We run a set of simulations considering different clump masses (M=10 - 200 M_{odot }) and impinging fluxes (G0 = 2
7 103 to 8
7 104 in Habing units). In the initial phase, the radiation sweeps the clump as an R-type dissociation front, reducing the H2 mass by a factor 40 - 90{{ per cent}}. Then, a weak (M 3ceq 2) shock develops and travels towards the centre of the clump, which collapses while losing mass from its surface. All considered clumps remain gravitationally unstable even if radiation rips off most of the clump mass, showing that external FUV radiation is not able to stop clump collapse. However, the FUV intensity regulates the final H2 mass available for star formation: for example, for G0 < 104 more than 10 per cent of the initial clump mass survives. Finally, for massive clumps ({ 73 } 100 M_{odot }) the H2 mass increases by 25 - 50{{ per cent}} during the collapse, mostly because of the rapid density growth that implies a more efficient H2 self-shielding
Growth rates and age at adult size of loggerhead sea turtles (<em>Caretta caretta</em>) in the Mediterranean Sea, estimated through capture-mark-recapture records
A partir de registros de capturamarcaje- recaptura, se estimaron por primera vez en el Mediterráneo las tasas de crecimiento de las fases juveniles de la tortuga boba (Caretta caretta). Se liberaron treinta y ocho tortugas a partir de la costa italiana y se reencontraron después de 1.0-10.9 años en el periodo 1986-2007. El promedio de LCC (longitud curvada del caparazón) varió de 32.5 a 82.0 cm y se observaron tasas de crecimiento variables, de 0 a 5.97 cm/año (promedio: 2.5). La asociación entre la tasa de crecimiento anual y tres covariables (año promedio, talla promedio e intervalo de tiempo) se investigó a través de un modelo no-paramétrico. Solamente la talla media mostró un claro efecto en la tasa de crecimiento, descrito por una curva monotónica descendente. La variabilidad observada indica que factores no incluidos en el modelo, probablemente relacionados con el individuo, tienen un importante efecto en las tasas de crecimiento. En base a la función de crecimiento monotónicamente decreciente que indica que no hay esfuerzo en el crecimiento, se uso una función de crecimiento de von Bertalanffy para estimar el tiempo requerido por las tortugas para crecer dentro del rango de tallas observado. Los resultados indican que las tortugas necesitarán de 16-28 años para alcanzar 66.5-84.7 cm LCC, la talla promedio de anidación observada en las más importantes áreas de anidación del Mediterráneo, lo que puede ser considerado como una aproximación a la talla de madurez
Effects of Ga+ milling on InGaAsP Quantum Well Laser with mirrors etched by Focused Ion Beam
InGaAsP/InP quantum wells (QW) ridge waveguide lasers were fabricated for the
evaluation of Ga+ Focused Ion Beam (FIB) milling of mirrors. Electrical and
optical proprieties were investigated. A 7% increment in threshold current, a
17% reduction in external quantum efficiency and 15 nm blue shift in the
emission spectrum were observed after milling as compared to the as cleaved
facet result. Annealing in inert atmosphere partially revert these effects
resulting in 4% increment in threshold current, 11% reduction in external
efficiency and 13 nm blue shift with the as cleaved result. The current-voltage
behavior after milling and annealing shows a very small increase in leakage
current indicating that optical damage is the main effect of the milling
process.Comment: 12 pages, 4 figure
ALMA reveals metals yet no dust within multiple components in CR7
We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [CII] line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Ly emitting galaxy at that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [CII] emission. The two most luminous components in [CII] coincide with the brightest UV components (A and B), blue-shifted by km s with respect to the peak of Ly emission. Other [CII] components are observed close to UV clumps B and C and are blue-shifted by and km s with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3 limiting luminosity L0.1\rm Z/Z_{\odot}0.2$. The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early Universe through complex accretion of satellites
Resolved UV and [C II] Structures of Luminous Galaxies within the Epoch of Reionization
We present new deep ALMA and HST/WFC3 observations of MASOSA and VR7, two luminous Ly emitters (LAEs) at , for which the UV continuum level differ by a factor four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M, compact size and very high Ly EW A, is undetected in [CII] to a limit of L$_{\rm [CII]
The ALPINE-ALMA [CII] survey: Star-formation-driven outflows and circumgalactic enrichment in the early Universe
We study the efficiency of galactic feedback in the early Universe by
stacking the [C II] 158 um 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. The significance of these features increases when stacking the subset of galaxies with star formation rates (SFRs) higher than the median (SFRmed = 25 Msun/yr), 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) 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 epochs
The ALPINE-ALMA [C II] survey : star-formation-driven outflows and circumgalactic enrichment in the early Universe
We 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 epochs
The ALPINE-ALMA [C II] Survey: [C II]158micron Emission Line Luminosity Functions at
We present the [CII]158m line luminosity functions (LFs) at
using the ALMA observations of 118 sources, which are selected to have UV
luminosity and optical spectroscopic redshifts in COSMOS and
ECDF-S. Of the 118 targets, 75 have significant [CII] detections and 43 are
upper limits. This is by far the largest sample of [CII] detections which
allows us to set constraints to the volume density of [CII] emitters at
. But because this is a UV-selected sample, we are missing
[CII]-bright but UV-faint sources making our constraints strict lower limits.
Our derived LFs are statistically consistent with the [CII] LF at
. We compare our results with the upper limits of
the [CII] LF derived from serendipitous sources in the ALPINE maps (Loiacono et
al. 2020). We also infer the [CII] LFs based on published far-IR and CO LFs at
. Combining our robust lower limits with these additional estimates,
we set further constraints to the true number density of [CII] emitters at
. These additional LF estimates are largely above our LF at
, suggesting that UV-faint but [CII]-bright sources
likely make a significant contributions to the [CII] emitter volume density.
When we include all the LF estimates, we find that available model predictions
underestimate the number densities of [CII] emitters at . Finally, we
set a constraint on the molecular gas mass density at , with
\,Mpc. This is broadly
consistent with previous studies.Comment: 17 pages, 9 Figures, Update to match with the published version.
Accepted for the publication in Ap
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