14 research outputs found
The physical origins of gas in the circumgalactic medium using observationally-motivated TNG50 mocks
Absorbers in the spectrum of background objects probe the circumgalactic
medium (CGM) surrounding galaxies, but its physical properties remain
unconstrained. We use the cosmological hydrodynamical simulation TNG50 to
statistically trace the origins of HI Ly- absorbers around galaxies at
with stellar masses ranging from 10 to 10 M. We
emulate observational CGM studies by considering all gas within a line of sight
velocity range of km s from the central, to quantitatively
assess the impact of other galaxy haloes and overdense gas in the IGM that
intersect sightlines. The impact of satellites to the total absorber fraction
is most significant at impact parameters
and satellites with masses below typical detection limits (
M) account for 10 (40) per cent of absorbers that intersect any
satellite bound to and M centrals. After
confirming outflows are more dominant along the minor axis, we additionally
show that at least 20 per cent of absorbers exhibit no significant radial
movement, indicating that absorbers can also trace quasi-static gas. The
metallicity of absorbers also depends on the azimuthal angle, but this signal
is largely driven by enriched inflowing and quasi-static gas. Our work shows
that determining the stellar mass of galaxies at is essential to
constrain the physical origin of the gas traced in absorption, which in turn is
key to characterising the kinematics and distribution of gas and metals in the
CGM.Comment: 23 pages, 13 figures. Accepted for publication in MNRA
The H{\alpha} Luminosity Function of Galaxies at z {\sim} 4.5
We present the H{\alpha} luminosity function (LF) derived from a large sample
of Lyman break galaxies at z {\sim} 4.5 over the GOODS-South and North fields.
This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5]
imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer
program. The H{\alpha} flux is derived from the offset between the continuum
flux estimated from the best-fit spectral energy distribution, and the observed
photometry in IRAC [3.6]. From these measurements, we build the H{\alpha} LF
and study its evolution providing the best constraints of this property at high
redshift, where spectroscopy of H{\alpha} is not yet available. Schechter
parameterizations of the H{\alpha} LF show a decreasing evolution of
{\Phi^\star} with redshift, increasing evolution in L{^\star}, and no
significant evolution in the faint-end slope at high z. We find that star
formation rates (SFRs) derived from H{\alpha} are higher than those derived
from the rest-frame UV for low SFR galaxies but the opposite happens for the
highest SFRs. This can be explained by lower mass galaxies (also lower SFR)
having, on average, rising star formation histories (SFHs), while at the
highest masses the SFHs may be declining. The SFR function is steeper, and
because of the excess SFR(H{\alpha}) compared to SFR(UV) at low SFRs, the SFR
density estimated from H{\alpha} is higher than the previous estimates based on
UV luminosities.Comment: Astrophysical Journal, Accepted, 17 pages, 16 figure
The BarYon CYCLE Project (ByCycle): Identifying and Localizing MgII Metal Absorbers with Machine Learning
The upcoming ByCycle project on the VISTA/4MOST multi-object spectrograph
will offer new prospects of using a massive sample of million high
spectral resolution ( = 20,000) background quasars to map the circumgalactic
metal content of foreground galaxies (observed at = 4000 - 7000), as traced
by metal absorption. Such large surveys require specialized analysis
methodologies. In the absence of early data, we instead produce synthetic 4MOST
high-resolution fibre quasar spectra. To do so, we use the TNG50 cosmological
magnetohydrodynamical simulation, combining photo-ionization post-processing
and ray tracing, to capture MgII (, ) absorbers. We
then use this sample to train a Convolutional Neural Network (CNN) which
searches for, and estimates the redshift of, MgII absorbers within these
spectra. For a test sample of quasar spectra with uniformly distributed
properties (, \AA, ), the algorithm has a robust
classification accuracy of 98.6 per cent and a mean wavelength accuracy of 6.9
\AA. For high signal-to-noise spectra (), the algorithm robustly
detects and localizes MgII absorbers down to equivalent widths of
\AA. For the lowest SNR spectra
(), the CNN reliably recovers and localizes
EW 0.75 \AA\, absorbers. This is more
than sufficient for subsequent Voigt profile fitting to characterize the
detected MgII absorbers. We make the code publicly available through GitHub.
Our work provides a proof-of-concept for future analyses of quasar spectra
datasets numbering in the millions, soon to be delivered by the next generation
of surveys.Comment: 13 pages, 9 figures, 1 table. Accepted for publication in MNRA
ALMACAL. XI. Over-densities as signposts to proto-clusters? A cautionary tale
It may be unsurprising that the most common approach to finding
proto-clusters is to search for over-densities of galaxies. Upgrades to
submillimetre (submm) interferometers and the advent of the James Webb Space
Telescope will soon offer the opportunity to find more distant candidate
proto-clusters in deep sky surveys without any spectroscopic confirmation. In
this letter, we report the serendipitous discovery of an extremely dense region
centred on the blazar, J0217-0820, at z=0.6 in the ALMACAL sky survey. Its
density is eight times higher than that predicted by blind submm surveys. Among
the seven submm-bright galaxies, three are as bright as conventional
single-dish submm galaxies, with S_870um > 3mJy. The over-density is thus
comparable to the densest known and confirmed proto-cluster cores. However,
their spectra betray a wide range of redshifts. We investigate the likelihood
of line-of-sight projection effects using light cones from cosmological
simulations, finding that the deeper we search, the higher the chance that we
will suffer from such projection effects. The extreme over-density around
J0217-0820 demonstrates the strong cosmic variance we may encounter in the deep
submm surveys. Thus, we should also question the fidelity of galaxy
proto-cluster candidates selected via over-densities of galaxies, where the
negative K correction eases the detection of dusty galaxies along an
extraordinarily extended line of sight.Comment: 7 pages, 5 figures, update with the accepted versio
MUSE-ALMA Halos XI: Gas flows in the circumgalactic medium
The flow of gas into and out of galaxies leaves traces in the circumgalactic
medium which can then be studied using absorption lines towards background
quasars. We analyse 27 log(N_HI) > 18.0 HI absorbers at z = 0.2 to 1.4 from the
MUSE-ALMA Halos survey with at least one galaxy counterpart within a line of
sight velocity of +/-500 km s^{-1}. We perform 3D kinematic forward modelling
of these associated galaxies to examine the flow of dense, neutral gas in the
circumgalactic medium. From the VLT/MUSE, HST broadband imaging and VLT/UVES
and Keck/HIRES high-resolution UV quasar spectroscopy observations, we compare
the impact parameters, star-formation rates and stellar masses of the
associated galaxies with the absorber properties. We find marginal evidence for
a bimodal distribution in azimuthal angles for strong HI absorbers, similar to
previous studies of the MgII and OVI absorption lines. There is no clear
metallicity dependence on azimuthal angle and we suggest a larger sample of
absorbers are required to fully test the relationship predicted by cosmological
hydrodynamical simulations. A case-by-case study of the absorbers reveals that
ten per cent of absorbers are consistent with gas accretion, up to 30 per cent
trace outflows while the remainder trace gas in the galaxy disk, the intragroup
medium and low-mass galaxies below the MUSE detection limit. Our results
highlight that the baryon cycle directly affects the dense neutral gas required
for star-formation and plays a critical role in galaxy evolution.Comment: 13 pages, 6 figures, 12 pages of appendix. Accepted for publication
in MNRA
ProgramaciĂłn Anual de FĂsica y desarrollo de la SituaciĂłn de Aprendizaje "ÂżDe quĂ© estĂĄ hecha la luz?"
En el presente Trabajo de Fin de MÂŽaster se elabora una ProgramaciÂŽon DidÂŽactica
Anual para la asignatura de FŽısica de 2Âș de Bachillerato del Instituto de EducaciÂŽon
Secundaria Granadilla de Abona. Dicha programaciÂŽon pretende solventar algunas
de las debilidades detectadas en la programaciÂŽon de este mismo centro. Para ello,
nos apoyaremos en el formato de SituaciŽon de Aprendizaje como herramienta para abordar contenidos, siendo la metodologŽıa constructivista el eje central de las
mismas. Finalmente se desarrolla con mÂŽas detalle una de las Situaciones de Aprendizaje propuestas: ÂżDe quÂŽe estÂŽa hecha la luz?In this Master Thesis I develop a year syllabus (programaciÂŽon anual didÂŽactica)
for the Physics course of the second year of Bachillerato in the IES Granadilla de
Abona. This aims to address some of the issues detected in the current syllabus
by using some alternative methodologies. In particular, we rely on the learning
scenarios approach, working from a constructivist perspective. Finally, one of the
proposed learning scenarios (What is light made of ? ) is developed in detail
Quaternized chitosan as support for the assembly of gold nanoparticles and glucose oxidase: Physicochemical characterization of the platform and evaluation of its biocatalytic activity
We report for the first time the use of quaternized chitosan (QCHI) for the immobilization of gold nanoparticles (NP) and glucose oxidase (GOD), the characterization of the resulting platform and its biocatalytic activity using glucose as substrate. The chemical substitution of chitosan has allowed us to work at physiologic pH to build up self-assembled layers of QCHI-NP as platform for the enzyme immobilization. The adsorption of GOD was analyzed by surface plasmon resonance (SPR) to compare the surface coverage of GOD in absence and presence of the QCHI-NP platform. The results obtained with cyclic voltammetry and scanning electrochemical microscopy (SECM) revealed that the adsorption of NP improves the conductivity of the structure and its electrochemical reactivity, facilitating the oxidation of the hydrogen peroxide produced by GOD. The electrodes modified with NP present higher amperometric response demonstrating the efficient transduction of the enzymatic activity in this structure. © 2010 Elsevier Ltd. All rights reserved.Fil: Bracamonte, Maria Victoria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; ArgentinaFil: Bollo, Soledad. Universidad de Chile; ChileFil: LabbĂ©, Pierre. Universite Joseph Fourier; FranciaFil: Rivas, Gustavo Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; ArgentinaFil: Ferreyra, Nancy Fabiana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; Argentin
Physico-chemical characterization of ferrocenyl-modified hyperbranched poly(ethylenimine) self-assembled multilayers
In this work, we characterize the electrochemical behavior of a new ferrocenyl-modified, hyperbranched poly(ethylenimine) (HBPei-Fc). The effects of the ionic strength, pH and the nature of the anion of the supporting electrolyte on the electrochemical behavior of the redox polymer were studied using cyclic voltammetry and an electrochemical quartz crystal microbalance. The interactions of the polymer with the anions of the supporting electrolyte, which was incorporated during the redox process, determined the electrochemical behavior that was observed. The polymer was employed for the construction of layer-by-layer-assembled multi-composite films using thiolated gold surfaces with HBPei-Fc as the polycation and citrate-stabilized gold nanoparticles or glucose oxidase (GOx) as the negative polyelectrolyte. The self-assembled multilayers were characterized using UVâVis spectrophotometry and electrochemical techniques to follow the signal of the ferrocene groups of the polymer. The adsorption of the polymer and GOx was analyzed using surface plasmon resonance to determine the surface coverage and the kinetic properties of the process. The results demonstrated that the ferrocenyl-modified polymer is an efficient platform for the immobilization of both inorganic materials, such as metallic nanoparticles, and biomolecules.Fil: Bracamonte, Maria Victoria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; ArgentinaFil: Yañez Soto, Claudia Andrea. Universidad de Chile; ChileFil: Bollo, Soledad. Universidad de Chile; ChileFil: Rivas, Gustavo Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; ArgentinaFil: Ferreyra, Nancy Fabiana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Instituto de Investigaciones en FĂsico-quĂmica de CĂłrdoba; Argentin
The physical origins of gas in the circumgalactic medium using observationally motivated TNG50 mocks
International audienceAbsorbers in the spectrum of background objects probe the circumgalactic medium (CGM) surrounding galaxies, but its physical properties remain unconstrained. We use the cosmological hydrodynamical simulation TNG50 to statistically trace the origins of Ly α absorbers around galaxies at z = 0.5 with stellar masses ranging from 108 to 1011 Mâ. We emulate observational CGM studies by considering all gas within a line of sight velocity range of ±500 kms-1 from the central, to quantitatively assess the impact of other galaxy haloes and overdense gas in the IGM that intersect sightlines. We find that 75 per cent of absorbers with column densities \log [N(\mbox{{\rm H\, {\small I}}})/\rm {cm}^{-2}] 16.0 trace the central galaxy within ±150 (80) kms-1 of M* = 1010(108) Mâ central galaxies. The impact of satellites to the total absorber fraction is most significant at impact parameters 0.5Rvir vir, and satellites with masses below typical detection limits (M* 8 Mâ) account for 10 (40) per cent of absorbers that intersect any satellite bound to 1010 and 1011 (109) Mâ centrals. After confirming outflows are more dominant along the minor axis, we additionally show that at least 20 per cent of absorbers exhibit no significant radial movement, indicating that absorbers can also trace quasi-static gas. Our work shows that determining the stellar mass of galaxies at zabs is essential to constrain the physical origin of the gas traced in absorption, which in turn is key to characterizing the kinematics and distribution of gas and metals in the CGM
The Hα Luminosity Function of Galaxies at z ⌠4.5
We present the H α luminosity function (LF) derived from a large sample of Lyman break galaxies at z ⌠4.5 over the GOODS-South and North fields. This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5] imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer program. The H α flux is derived from the offset between the continuum flux estimated from the best-fit spectral energy distribution, and the observed photometry in IRAC [3.6]. From these measurements, we build the H α LF and study its evolution providing the best constraints of this property at high redshift, where spectroscopy of H α is not yet available. Schechter parameterizations of the H α LF show a decreasing evolution of Ί ^â with redshift, increasing evolution in L ^â , and no significant evolution in the faint-end slope at high z . We find that star formation rates (SFRs) derived from H α are higher than those derived from the rest-frame UV for low SFR galaxies but the opposite happens for the highest SFRs. This can be explained by lower mass galaxies (also lower SFR) having, on average, rising star formation histories (SFHs), while at the highest masses the SFHs may be declining. The SFR function is steeper, and because of the excess SFR(H α ) compared to SFR(UV) at low SFRs, the SFR density estimated from H α is higher than the previous estimates based on UV luminosities