arXiv subjects

C. E. Barbosa

Publications and source records attributed to C. E. Barbosa.

16 recordsLinked to original sources

arXiv2022

Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes). III. The Southern SMUDGes Catalog

We present a catalog of 5598 ultra-diffuse galaxy (UDG) candidates with effective radius $r_e > 5.3$ arcsec distributed throughout the southern portion of the DESI Legacy Imaging Survey covering $\sim$ 15000 deg$^2$. The catalog is most complete for physically large ($r_e > 2.5$ kpc) UDGs lying in the redshift range $1800 \lesssim cz/{\rm km\ s}^{-1} \lesssim 7000$, where the lower bound is defined by where incompleteness becomes significant for large objects on the sky and the upper bound by our minimum angular size selection criterion. Because physical size is integral to the definition of a UDG, we develop a method {of distance estimation} using existing redshift surveys. With three different galaxy samples, two of which contain UDGs with spectroscopic redshifts, we estimate that the method has a redshift accuracy of $\sim$ 75% when the method converges, although larger, more representative spectroscopic UDG samples are needed to fully understand the behavior of the method. We are able to estimate distances for 1079 of our UDG candidates (19%). Finally, to illustrate uses of the catalog, we present distance independent and dependent results. In the latter category we establish that the red sequence of UDGs lies on the extrapolation of the red sequence relation for bright ellipticals and that the environment-color relation is at least qualitatively similar to that of high surface brightness galaxies. Both of these results challenge some of the models proposed for UDG evolution.

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arXiv2021

On the discovery of stars, quasars, and galaxies in the Southern Hemisphere with S-PLUS DR2

This paper provides a catalogue of stars, quasars, and galaxies for the Southern Photometric Local Universe Survey Data Release 2 (S-PLUS DR2) in the Stripe 82 region. We show that a 12-band filter system (5 Sloan-like and 7 narrow bands) allows better performance for object classification than the usual analysis based solely on broad bands (regardless of infrared information). Moreover, we show that our classification is robust against missing values. Using spectroscopically confirmed sources retrieved from the Sloan Digital Sky Survey DR16 and DR14Q, we train a random forest classifier with the 12 S-PLUS magnitudes + 4 morphological features. A second random forest classifier is trained with the addition of the W1 (3.4 $μ$m) and W2 (4.6 $μ$m) magnitudes from the Wide-field Infrared Survey Explorer (WISE). Forty-four percent of our catalogue have WISE counterparts and are provided with classification from both models. We achieve 95.76% (52.47%) of quasar purity, 95.88% (92.24%) of quasar completeness, 99.44% (98.17%) of star purity, 98.22% (78.56%) of star completeness, 98.04% (81.39%) of galaxy purity, and 98.8% (85.37%) of galaxy completeness for the first (second) classifier, for which the metrics were calculated on objects with (without) WISE counterpart. A total of 2,926,787 objects that are not in our spectroscopic sample were labelled, obtaining 335,956 quasars, 1,347,340 stars, and 1,243,391 galaxies. From those, 7.4%, 76.0%, and 58.4% were classified with probabilities above 80%. The catalogue with classification and probabilities for Stripe 82 S-PLUS DR2 is available for download.

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arXiv2021

Canis Major OB1 stellar groups contents revealed by Gaia

Canis Major OB1 (CMa OB1) is a Galactic stellar association with a very intriguing star-formation scenario. There are more than two dozen known star clusters in its line of sight, but it is not clear which ones are physically associated with CMa OB1. We use a clustering code that employs 5-dimensional data from the Gaia DR2 catalogue to identify physical groups and obtain their astrometric parameters and, in addition, we use two different isochrone-fitting methods to estimate the ages of these groups. We find 15 stellar groups with distances between 570 pc and 1650 pc, including 10 previously known and 5 new open cluster candidates. Four groups, precisely the youngest ones ($<$ 20 Myr), CMa05, CMa06, CMa07 and CMa08, are confirmed to be part of CMa OB1. We find that CMa08, a new cluster candidate, may be the progenitor cluster of runaway stars. CMa06 coincides with the well-studied CMa R1 star-forming region. While CMa06 is still forming stars, due to the remaining material of the molecular cloud associated with the Sh 2-262 nebula, CMa05, CMa07 and CMa08 seem to be in more evolved stages of evolution, with no recent star-forming activity. The properties of these CMa OB1 physical groups fit well in a monolithic scenario of star formation, with a common formation mechanism, and having suffered multiple episodes of star formation. This suggests that the hierarchical model alone, which explains the populations of other parts of the same association, is not sufficient to explain its whole formation history.

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arXiv2021

Pixel color-magnitude diagrams of galaxies in the Fornax cluster using S-PLUS images

Galaxy clusters are the largest gravitationally bound systems in the Universe and, as such, play an important role in cosmological studies. An important resource for studying their properties in a statistical manner are homogeneous and large image datasets covering diverse environments. In this sense, the wide-field images (1.4 deg^{2}) obtained by the Southern Photometric Local Universe Survey (S-PLUS) in 12 optical bands, constitute a valuable tool for that type of studies. In this work, we present a photometric analysis of pixel color-magnitude diagrams, corresponding to a sample of 24 galaxies of different morphological types located in the Fornax cluster.

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arXiv2021

The Fornax Cluster through S-PLUS

The Southern Photometric Local Universe Survey (S-PLUS) aims to map $\approx$ 9300 deg$^2$ of the Southern sky using the Javalambre filter system of 12 optical bands, 5 Sloan-like filters and 7 narrow-band filters centered on several prominent stellar features ([OII], Ca H+K, D4000, H$_δ$, Mgb, H$_α$ and CaT). S-PLUS is carried out with the T80-South, a new robotic 0.826-m telescope located on CTIO, equipped with a wide FoV camera (2 deg$^2$). In this poster we introduce project #59 of the S-PLUS collaboration aimed at studying the Fornax galaxy cluster covering an sky area of $\approx$ 11 $\times$ 7 deg$^2$, and with homogeneous photometry in the 12 optical bands of S-PLUS (Coordinator: A. Smith Castelli).

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arXiv2021

Data Release 2 of S-PLUS: accurate template-fitting based photometry covering $\sim$1000 square degrees in 12 optical filters

The Southern Photometric Local Universe Survey (S-PLUS) is an ongoing survey of $\sim$9300 deg$^2$ in the southern sky in a 12-band photometric system. This paper presents the second data release (DR2) of S-PLUS, consisting of 514 tiles covering an area of 950 deg$^2$. The data has been fully calibrated using a new photometric calibration technique suitable for the new generation of wide-field multi-filter surveys. This technique consists of a $χ^2$ minimisation to fit synthetic stellar templates to already calibrated data from other surveys, eliminating the need for standard stars and reducing the survey duration by $\sim$15\%. We compare the template-predicted and S-PLUS instrumental magnitudes to derive the photometric zero-points (ZPs). We show that these ZPs can be further refined by fitting the stellar templates to the 12 S-PLUS magnitudes, which better constrain the models by adding the narrow-band information. We use the STRIPE82 region to estimate ZP errors, which are $\lesssim10$ mmags for filters J0410, J0430, $g$, J0515, $r$, J0660, $i$, J0861 and $z$; $\lesssim 15$ mmags for filter J0378; and $\lesssim 25$ mmags for filters $u$ and J0395. We describe the complete data flow of the S-PLUS/DR2 from observations to the final catalogues and present a brief characterisation of the data. We show that, for a minimum signal-to-noise threshold of 3, the photometric depths of the DR2 range from 19.9 mag to 21.3 mag (measured in Petrosian apertures), depending on the filter. The S-PLUS DR2 can be accessed from the website: https://splus.cloud}{https://splus.cloud.

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arXiv2021

A preserved high-z compact progenitor in the heart of NGC3311 revealed with MUSE 2D stellar population analysis

Massive early-type galaxies are believed to be the end result of an extended mass accretion history. The stars formed in situ very early on in the initial phase of the assembly might have originated from an extremely intense star formation burst, and may still be found within the cores of such galaxies today. We investigate the presence of a surviving high-$z$ compact progenitor component in the brightest galaxy of the Hydra I cluster, NGC 3311, by mapping its 2D kinematics and stellar population out to 2 effective radii, combining MUSE observations, extended EMILES models, and a newly developed parametric fully Bayesian framework using full-spectrum fitting. We present 2D maps and radial profiles of the stellar velocity dispersion, age, total metallicity, $α$-element, sodium abundance ([Na/Fe]), and the initial mass function (IMF) slope. All properties have significant gradients, confirming the existence of multiple structural components, including a young, metal-rich "blue spot". We find that the component dominating the light budget of NGC 3311 within $R\lesssim 2.0$ kpc is the surviving $z=0$ analog of a high-$z$ compact core. This concentrated structure has a relatively small velocity dispersion ($σ_*\approx 180$ km s$^{-1}$), is very old (ages$\gtrsim 11$ Gyr), metal-rich ([Z/H]$\sim0.2$ and [Na/Fe]$\sim0.4$), and has a bottom-heavy IMF (with slope $Γ_b\sim2.4$). In the outer region, stars become increasingly hotter, younger, metal and sodium poorer, $α$-element richer, and the IMF slope becomes Chabrier-like. The multiple structural components in NGC 3311 confirm the predictions from the two-phase formation scenario for NGC 3311. Interestingly, the outer stellar population has an overabundant [$α$/Fe], most likely because NGC 3311, located at the center of the galaxy cluster, accreted stars from rapidly quenched satellites.[Abridged]

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arXiv2021

Physical and kinematic conditions of the local merging galaxy NGC 1487

We present optical VLT/MUSE integral field spectroscopy data of the merging galaxy NGC 1487. We use fitting techniques to study the ionized gas emission of this merger and its main morphological and kinematical properties. We measured flat and sometimes inverted oxygen abundance gradients in the subsystems composing NGC 1487, explained by metal mixing processes common in merging galaxies. We also measured widespread star-forming bursts, indicating that photoionisation by stars is the primary ionization source of the galaxy. The kinematic map revealed a rotating pattern in the gas in the northern tail of the system, suggesting that the galaxy may be in the process of rebuilding a disc. The gas located in the central region has larger velocity dispersion ($σ\approx 50$ km s$^{-1}$) than the remaining regions, indicating kinematic heating, possibly owing to the ongoing interaction. Similar trends were, however, not observed in the stellar velocity-dispersion map, indicating that the galaxy has not yet achieved equilibrium, and the nebular and stellar components are still kinematically decoupled. Based on all our measurements and findings, and specially on the mass estimates, metallicity gradients and velocity fields of the system, we propose that NGC 1487 is the result of an ongoing merger event involving smallish dwarf galaxies within a group, in a pre-merger phase, resulting in a relic with mass and physical parameters similar to a dwarf galaxy. Thus, we may be witnessing the formation of a dwarf galaxy by merging of smaller clumps at z=0.

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arXiv2020

What does (not) drive the variation of the low-mass end of the stellar initial mass function of early-type galaxies

The stellar initial mass function (IMF) seems to be variable and not universal, as argued in the literature in the last three decades. Several relations among the low-mass end of the IMF slope and other stellar population, photometric or kinematic parameters of massive early-type galaxies (ETGs) have been proposed, but a consolidated agreement on a factual cause of the observed variations has not been reached yet. We investigate the relations between the IMF and other stellar population parameters in NGC 3311, the central galaxy of the Hydra I cluster. NGC 3311 is characterized by old and metal-rich stars, like other massive ETGs, but has unusual increasing stellar velocity dispersion and [$α/$Fe] profiles. We use spatially resolved MUSE observations to obtain stellar population properties using Bayesian full-spectrum fitting in the central part of NGC 3311 to compare the IMF slope against other stellar parameters with the goal of assessing their relations/dependencies. For NGC 3311, we unambiguously invalidate the previously observed direct correlation between the IMF slope and the local stellar velocity dispersion, confirming some doubts already raised in the literature. This relation may arise as a spatial coincidence only, between the region with the largest stellar velocity dispersion, with that where the oldest, $\textit{in situ}$ population is found and dominates. We also show robust evidence that the proposed IMF-metallicity relation is contaminated by the degeneracy between these two parameters. The tightest correlations we found are those between stellar age and IMF and between galactocentric radius and IMF. The variation of the IMF is not due to kinematical, dynamical, or global properties in NGC 3311. We speculate that IMF might be dwarf-dominated in the "red-nuggets" formed at high redshifts that ended up being the central cores of today's giant ellipticals. [Abridged]

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arXiv2020

Dust and star formation in the centre of NGC 3311

NGC 3311 is the central galaxy of the Hydra I galaxy cluster. It has a hot interstellar medium and hosts a central dust lane with emission lines. These dust lanes are frequent in elliptical galaxies, but the case of NGC 3311 might be particularly interesting for problems of dust lifetime and the role of cool gas in the central parts. We aim to use archival HST images and MUSE data to investigate the central dust structure of NGC 3311. We used the tool PyParadise to model the stellar population and extract the emission lines. The HST/ACS colour map reveals the known dust structures, but also blue spots, which are places of strong line emission. A dusty 'mini-jet' emanates from the centre. The distribution of the emission line gas matches the dust silhouette almost exactly. Close to the brightest Halpha emission, the ratio [NII]/Halpha resembles that of HII-regions; in the outer parts, [NII] gets stronger and is similar to LINER-like spectra. The gas kinematics is consistent with that of a rotating disc. The Doppler shifts of the strongest line emissions, which indicate the areas of highest star formation activity, smoothly fit into the disc symmetry. The metallicity is supersolar. The presence of neutral gas is indicated by the fit residuals of the stellar NaI D absorption line, which we interpret as interstellar absorption. We estimate the mass of the neutral gas to be of the order of the X-ray mass. The dynamical mass infers a stellar population of intermediate age, whose globular clusters have already been identified. Our findings can be harmonised in a scenario in which the star formation is triggered by the accretion of cold gas onto a pre-existing gas/dust disc or ring. Newly produced dust then contributes to the longevity of the dust.

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arXiv2020

One hundred SMUDGes in S-PLUS: ultra-diffuse galaxies flourish in the field

We present the first systematic study of the stellar populations of ultra-diffuse galaxies (UDGs) in the field, integrating the large area search and characterization of UDGs by the SMUDGes survey with the twelve-band optical photometry of the S-PLUS survey. Based on Bayesian modeling of the optical colors of UDGs, we determine the ages, metallicities and stellar masses of 100 UDGs distributed in an area of $\sim 330$ deg$^2$ in the Stripe 82 region. We find that the stellar masses and metallicities of field UDGs are similar to those observed in clusters and follow the trends previously defined in studies of dwarf and giant galaxies. However, field UDGs have younger luminosity-weighted ages than do UDGs in clusters. We interpret this result to mean that field UDGs have more extended star formation histories, including some that continue to form stars at low levels to the present time. Finally, we examine stellar population scaling relations that show that UDGs are, as a population, similar to other low-surface brightness galaxies.

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arXiv2019

The S-PLUS: a star/galaxy classification based on a Machine Learning approach

We present a star/galaxy classification for the Southern Photometric Local Universe Survey (S-PLUS), based on a Machine Learning approach: the Random Forest algorithm. We train the algorithm using the S-PLUS optical photometry up to $r$=21, matched to SDSS/DR13, and morphological parameters. The metric of importance is defined as the relative decrease of the initial accuracy when all correlations related to a certain feature is vanished. In general, the broad photometric bands presented higher importance when compared to narrow ones. The influence of the morphological parameters has been evaluated training the RF with and without the inclusion of morphological parameters, presenting accuracy values of 95.0\% and 88.1\%, respectively. Particularly, the morphological parameter {\rm FWHM/PSF} performed the highest importance over all features to distinguish between stars and galaxies, indicating that it is crucial to classify objects into stars and galaxies. We investigate the misclassification of stars and galaxies in the broad-band colour-colour diagram $(g-r)$ versus $(r-i)$. The morphology can notably improve the classification of objects at regions in the diagram where the misclassification was relatively high. Consequently, it provides cleaner samples for statistical studies. The expected contamination rate of red galaxies as a function of the redshift is estimated, providing corrections for red galaxy samples. The classification of QSOs as extragalactic objects is slightly better using photometric-only case. An extragalactic point-source catalogue is provided using the classification without any morphology feature (only the SED information) with additional constraints on photometric redshifts and {\rm FWHM/PSF} values.

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arXiv2019

The Southern Photometric Local Universe Survey (S-PLUS): improved SEDs, morphologies and redshifts with 12 optical filters

The Southern Photometric Local Universe Survey (S-PLUS) is imaging ~9300 deg^2 of the celestial sphere in twelve optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-American Observatory, Chile. The telescope is equipped with a 9.2k by 9.2k e2v detector with 10 um pixels, resulting in a field-of-view of 2 deg^2 with a plate scale of 0.55"/pixel. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (8000 deg^2 at |b| > 30 deg) and two areas of the Galactic plane and bulge (for an additional 1300 deg^2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 u, g, r, i, z broad-band filters and 7 narrow-band filters centered on prominent stellar spectral features: the Balmer jump/[OII], Ca H+K, H-delta, G-band, Mg b triplet, H-alpha, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (delta_z/(1+z) = 0.02 or better) for galaxies with r < 20 AB mag and redshift < 0.5, thus producing a 3D map of the local Universe over a volume of more than 1 (Gpc/h)^3. The final S-PLUS catalogue will also enable the study of star formation and stellar populations in and around the Milky Way and nearby galaxies, as well as searches for quasars, variable sources, and low-metallicity stars. In this paper we introduce the main characteristics of the survey, illustrated with science verification data highlighting the unique capabilities of S-PLUS. We also present the first public data release of ~336 deg^2 of the Stripe-82 area, which is available at http://datalab.noao.edu/splus.

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arXiv2019

Assessing the photometric redshift precision of the S-PLUS survey: the Stripe-82 as a test-case

In this paper we present a thorough discussion about the photometric redshift (photo-z) performance of the Southern Photometric Local Universe Survey (S-PLUS). This survey combines a 7 narrow + 5 broad passband filter system, with a typical photometric-depth of r$\sim$21 AB. For this exercise, we utilize the Data Release 1 (DR1), corresponding to 336 deg$^{2}$ from the Stripe-82 region. We rely on the \texttt{BPZ2} code to compute our estimates, using a new library of SED models, which includes additional templates for quiescent galaxies. When compared to a spectroscopic redshift control sample of $\sim$100k galaxies, we find a precision of $σ_{z}<$0.8\%, $<$2.0\% or $<$3.0\% for galaxies with magnitudes r$<$17, $<$19 and $<$21, respectively. A precision of 0.6\% is attained for galaxies with the highest \texttt{Odds} values. These estimates have a negligible bias and a fraction of catastrophic outliers inferior to 1\%. We identify a redshift window (i.e., 0.26$<z<$0.32) where our estimates double their precision, due to the simultaneous detection of two emission-lines in two distinct narrow-bands; representing a window opportunity to conduct statistical studies such as luminosity functions. We forecast a total of $\sim$2M, $\sim$16M and $\sim$32M galaxies in the S-PLUS survey with a photo-z precision of $σ_{z}<$1.0\%, $<$2.0\% and $<$2.5\% after observing 8000 $deg^{2}$. We also derive redshift Probability Density Functions, proving their reliability encoding redshift uncertainties and their potential recovering the $n(z)$ of galaxies at $z<0.4$, with an unprecedented precision for a photometric survey in the southern hemisphere.

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arXiv2018

The Hydra I cluster core - II. Kinematic complexity in a rising velocity dispersion profile around the cD galaxy NGC 3311

NGC 3311, the central galaxy of the Hydra I cluster, shows signatures of recent infall of satellite galaxies from the cluster environment. Previous work has shown that the line-of-sight velocity dispersion of the stars and globular clusters in the extended halo of NGC 3311 rises up to the value of the cluster velocity dispersion. We performed multi-object spectroscopic observations of the diffuse stellar halo of NGC 3311 using VLT/FORS2 in MXU mode to mimic a coarse `IFU'. We use pPXF to extract the kinematic information. We find a homogeneous velocity and velocity dispersion field within r<10 kpc. Beyond this radius, both the velocities and dispersions start to depend on azimuth angle and show a significant intrinsic scatter. The inner spheroid of NGC 3311 can be described as a slow rotator. Outside 10 kpc the cumulative angular momentum is rising. If the radial dependence alone is considered, the velocity dispersion does not simply rise but fills an increasingly large range of values with two well defined envelopes. The lower envelope is about constant at 200 km/s. The upper envelope rises smoothly, joining the velocity dispersion of the outer cluster galaxies. We interpret this behaviour as the superposition of tracer populations with increasingly shallower radial distributions between the extremes of the inner stellar populations and the cluster galaxies. Simple Jeans models illustrate that a range of of mass profiles with different anisotropies can account for all observed velocity dispersions, including radial MOND models. Jeans models using one tracer population with a unique density profile are not able to explain the large range of the observed kinematics. Previous claims about the cored dark halo of NGC 3311 are therefore probably not valid. This may in general apply to central cluster galaxies with rising velocity dispersion profiles, where infall processes are important.

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arXiv2015

GHASP: an H$α$ kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc-band

We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP, Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which high-resolution Fabry-Perot Hα maps have previously been obtained. Our data set is constructed by new Rc-band observations taken at the Observatoire de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS) archival data, obtained with the purpose of deriving homogeneous photometric profiles and parameters. Our results include Rc-band surface brightness profiles for 170 galaxies and $ugriz$ profiles for 108 of these objects. We catalogue several parameters of general interest for further reference, such as total magnitude, effective radius and isophotal parameters -- magnitude, position angle, ellipticity and inclination. We also perform a structural decomposition of the surface brightness profiles using a multi-component method in order to separate disks from bulges and bars, and to observe the main scaling relations involving luminosities, sizes and maximum velocities. We determine the Rc-band Tully Fisher relation using maximum velocities derived solely from H$α$ rotation curves for a sample of 80 galaxies, resulting in a slope of $-8.1 \pm 0.5$, zero point of $-3.0 \pm 1.0$ and an estimated intrinsic scatter of $0.28 \pm 0.07$. We note that, different from the TF-relation in the near-infrared derived for the same sample, no change in the slope of the relation is seen at the low-mass end (for galaxies with $V_{max} < 125$ km/s). We suggest that this different behaviour of the Tully Fisher relation (with the optical relation being described by a single power-law while the near-infrared by two) may be caused by differences in the stellar mass to light ratio for galaxies with $V_{max} < 125$ km/s.

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