20 research outputs found
Measuring the physical imprints of gas flows in galaxies I: Accretion rate histories
Galaxies are expected to accrete pristine gas from their surroundings to
sustain their star formation over cosmic timescales. Its lower abundance
affects the metallicity of the ISM in which stars are born, leaving chemical
imprints in the stellar populations. We measure the amount of pristine gas that
galaxies accrete during their lifetime, using information on the ages and
abundances of their stellar populations and a chemical evolution model. We also
aim to determine the efficiency of star formation over time. We derived star
formation histories and metallicity histories for a sample of 8523 galaxies
from the MaNGA survey. We use the former to predict the evolution of the
metallicity in a closed-box scenario, and estimate for each epoch the gas
accretion rate required to match these predictions with the measured stellar
metallicity. Using only chemical parameters, we find that the history of gas
accretion depends on the mass of galaxies. More massive galaxies accrete more
gas and at higher redshifts than less massive galaxies, which accrete their gas
over longer periods. We also find that galaxies with a higher star formation
rate at z = 0 have a more persistent accretion history for a given mass. The
star formation efficiency shows similar correlations: early-type galaxies and
higher-mass galaxies had a higher efficiency in the past, and it declined such
that they are less efficient in the present. Our analysis of individual
galaxies shows that compactness affects the peak star formation efficiency that
galaxies reach, and that the slope of the efficiency history of galaxies with
current star formation is flat. Our results support the hypothesis that a
steady and substantial supply of pristine gas is required for persistent star
formation in galaxies. Once they lose access to this gas supply, star formation
comes to a halt.Comment: 17 pages, 11 figures. Accepted at A&
The Calar Alto Legacy Integral Field Area Survey: spatial resolved properties
We present the analysis performed using the pyPipe3D pipeline for the 895
galaxies that comprises the eCALIFA data release Sanchez et al. submitted, data
with a significantly improved spatial resolution (1.0-1.5"/FWHM). We include a
description of (i) the analysis performed by the pipeline, (ii) the adopted
datamodel for the derived spatially resolved properties and (iii) the catalog
of integrated, characteristics and slope of the radial gradients for a set of
observational and physical parameters derived for each galaxy. We illustrate
the results of the analysis (i) using the NGC\,2906 as an archetypal galaxy,
showing the spatial distribution of the different derived parameters and
exploring in detail the properties of the ionized gas, and (ii) showing
distribution of the spatial resolved ionized gas across the classical
[OIII]/H vs. [NII]/H for the whole galaxy sample. In general our
results agree with previous published ones, however, tracing radial patterns
and segregating individual ionized structures is improved when using the
current dataset. All the individual galaxy dataproducts and the catalog
discussed along this article are distributed as part of the eCALIFA data
release http://ifs.astroscu.unam.mx/CALIFA_WEB/public_html/Comment: 47 pages, 8 tables, 9 figures, submitted the 12th of April 2023 to
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FROM GLOBAL TO SPATIALLY RESOLVED IN LOW-REDSHIFT GALAXIES
Our understanding of the structure, composition and evolution of galaxies has strongly improved in the last decades, mostly due to new results based on large spectroscopic and imaging surveys. In particular, the nature of ionized gas, its ionization mechanisms, its relation with the stellar properties and chemical composition, the existence of scaling relations that describe the cycle between stars and gas, and the corresponding evolution patterns have been widely explored and described. More recently, the introduction of additional techniques, in particular integral field spectroscopy, and their use in large galaxy surveys, have forced us to re-interpret most of those recent results from a spatially resolved perspective. This review is aimed to complement recent efforts to compile and summarize this change of paradigm in the interpretation of galaxy evolution. To this end we replicate published results, and present novel ones, based on the largest compilation of IFS data of galaxies in the nearby universe to date. © 2021: Instituto de Astronomía, Universidad Nacional Autónoma de México
pyFIT3D and pyPipe3D -- The new version of the Integral Field Spectroscopy data analysis pipeline
We present a new version of the FIT3D and Pipe3D codes, two packages to
derive properties of the stellar populations and the ionized emission lines
from optical spectroscopy and integral field spectroscopy data respectively.
The new codes have been fully transcribed to Python from the original Perl and
C versions, modifying the algorithms when needed to make use of the unique
capabilities of this language with the main goals of (1) respecting as much as
possible the original philosophy of the algorithms, (2) maintaining a full
compatibility with the original version in terms of the format of the required
input and produced output files, and (3) improving the efficiency and accuracy
of the algorithms, and solving known (and newly discovered) bugs. The complete
package is freely distributed, with an available repository online. pyFIT3D and
pyPipe3D are fully tested with data of the most recent IFS data surveys and
compilations (e.g. CALIFA, MaNGA, SAMI and AMUSING++), and confronted with
simulations. We describe here the code, its new implementation, its accuracy in
recovering the parameters based on simulations, and a showcase of its
implementation on a particular dataset.Comment: New Astronomy - 29 pages, 19 figures - Received on 7 Dec 2021 -
Accepted for publication on 8 Jul 202
Kinematic Clues to Bar Evolution for Galaxies in the Local Universe: Why the Fastest Rotating Bars are Rotating Most Slowly
We have used Spitzer images of a sample of 68 barred spiral galaxies in the local universe to make systematic measurements of bar length and bar strength. We combine these with precise determinations of the corotation radii associated with the bars, taken from our previous study, which used the phase change from radial inflow to radial outflow of gas at corotation, based on high-resolution two-dimensional velocity fields in Hα taken with a Fabry-Pérot spectrometer. After presenting the histograms of the derived bar parameters, we study their dependence on the galaxy morphological type and on the total stellar mass of the host galaxy, and then produce a set of parametric plots. These include the bar pattern speed versus bar length, the pattern speed normalized with the characteristic pattern speed of the outer disk versus the bar strength, and the normalized pattern speed versus R, the ratio of corotation radius to bar length. To provide guidelines for our interpretation, we used recently published simulations, including disk and dark matter halo components. Our most striking conclusion is that bars with values of R < 1.4, previously considered dynamically fast rotators, can be among the slowest rotators both in absolute terms and when their pattern speeds are normalized. The simulations confirm that this is because as the bars are braked, they can grow longer more quickly than the outward drift of the corotation radius. We conclude that dark matter halos have indeed slowed down the rotation of bars on Gyr timescales. © 2017. The American Astronomical Society. All rights reserved.
Comparative internal kinematics of the H II regions in interacting and isolated galaxies: Implications for massive star formation modes
We have observed 12 interacting galaxy pairs using the Fabry-Perot interferometer GH αFaS (GalaxyHα Fabry-Perot system) on the 4.2-mWilliam Herschel Telescope at theObservatorio del Roque de los Muchachos, La Palma. We present here the Hα surface brightness, velocity and velocity dispersion maps for the 10 systems we have not previously observed using this technique, as well as the physical properties (sizes, Hα luminosities and velocity dispersion) of 1259 HII regions from the full sample. We also derive the physical properties of 1054 HII regions in a sample of 28 isolated galaxies observed with the same instrument in order to compare the two populations of HII regions. We find a population of the brightest HII regions for which the scaling relations, for example the relation between the Hα luminosity and the radius, are clearly distinct from the relations for the regions of lower luminosity. The regions in this bright population are more frequent in the interacting galaxies. We find that the turbulence, and also the star formation rate (SFR), are enhanced in the HII regions in the interacting galaxies. We have also extracted the Hα equivalent widths for the HII regions of both samples, and we have found that the distribution of HII region ages coincides for the two samples of galaxies. We suggest that the SFR enhancement is brought about by gas flows induced by the interactions, which give rise to gravitationally bound gas clouds which grow further by accretion from the flowing gas, producing conditions favourable to star formation. Key words: stars: formation -HII regions - galaxies: interactions - galaxies: ISM- galaxies: kinematics and dynamics
Parameters and models of the jets from Sanduleak’s star in the LMC
Context. Angeloni and collaborators have discovered a bipolar jet extending out to ~6 pc from “Sanduleak’s star” in the Large Magellanic Cloud (LMC). This is the first angularly resolved stellar jet system that has been observed outside our Galaxy.
Aims. In this paper we use archival Hubble Space Telescope (HST) images of this jet in order to estimate the flow parameters, and use them to explore two possible theoretical scenarios for modelling this bipolar outflow.
Methods. We have computed axisymmetric gasdynamic simulations of a conical outflow with an opening angle that increases with time and of a cylindrical jet interacting with a stratified circumstellar structure. The results of these models are then compared with the observed morphology of the jets from Sanduleak’s star.
Results. From the observations, we obtain Ṁj ≈ 1.2 × 10−5M⊙ yr−1 and Lm ≈ 1000 L⊙ for the mass loss rate and the mechanical luminosity (respectively) of each of the outflow lobes. We also obtain a (deprojected) flow velocity vj ≈ 1000 km s−1 and a dynamical time tdyn ≈ 7300 yr. From the simulations that we have computed (with these flow parameters), we find that both the “opening out conical wind” and the “jet+stratified environment” scenarios have characteristics that resemble the observed morphologies. A more complete model for the jets from Sanduleak’s star might incorporate some of the features of these two scenarios