35 research outputs found
Catalogue of the morphological features in the Spitzer Survey of Stellar Structure in Galaxies (SG)
A catalogue of the morphological features for the complete Spitzer Survey of
Stellar Structure in Galaxies (SG), including 2352 nearby galaxies, is
presented. The measurements are made using 3.6 m images, largely tracing
the old stellar population; at this wavelength the effects of dust are also
minimal. The measured features are the sizes, ellipticities, and orientations
of bars, rings, ringlenses, and lenses. Measured in a similar manner are also
barlenses (lens-like structures embedded in the bars), which are not lenses in
the usual sense, being rather the more face-on counterparts of the boxy/peanut
structures in the edge-on view. In addition, pitch angles of spiral arm
segments are measured for those galaxies where they can be reliably traced.
More than one pitch angle may appear for a single galaxy. All measurements are
made in a human-supervised manner so that attention is paid to each galaxy. We
used isophotal analysis, unsharp masking, and fitting ellipses to measured
structures. We find that the sizes of the inner rings and lenses normalized to
barlength correlate with the galaxy mass: the normalized sizes increase toward
the less massive galaxies; it has been suggested that this is related to the
larger dark matter content in the bar region in these systems. Bars in the low
mass galaxies are also less concentrated, likely to be connected to the mass
cut-off in the appearance of the nuclear rings and lenses. We also show
observational evidence that barlenses indeed form part of the bar, and that a
large fraction of the inner lenses in the non-barred galaxies could be former
barlenses in which the thin outer bar component has dissolved.Comment: 17 pages, 12 figures, accepted for publication in A&
Characterization of galactic bars from 3.6 Ό m S 4 G imaging
Context. Stellar bars play an essential role in the secular evolution of disk galaxies because they are responsible for the redistribution of matter and angular momentum. Dynamical models predict that bars become stronger and longer in time, while their rotation speed slows down. Aims. We use the Spitzer Survey of Stellar Structure in Galaxies (S4G) 3.6 ÎŒm imaging to study the properties (length and strength) and fraction of bars at z = 0 over a wide range of galaxy masses (Mâ â 108â1011 Mâ) and Hubble types (â3 †T †10).Methods. We calculated gravitational forces from the 3.6 ÎŒm images for galaxies with a disk inclination lower than 65°. We used the maximum of the tangential-to-radial force ratio in the bar region (Qb) as a measure of the bar-induced perturbation strength for a sample of ~600 barred galaxies. We also used the maximum of the normalized m = 2 Fourier density amplitude (A2max) to characterize the bar. Bar sizes were estimated i) visually; ii) from ellipse fitting; iii) from the radii of the strongest torque; and iv) from the radii of the largest m = 2 Fourier amplitude in the bar region. By combining our force calculations with the Hâi kinematics from the literature, we estimated the ratio of the halo-to-stellar mass (Mh/Mâ) within the optical disk and by further using the universal rotation curve models, we obtained a first-order model of the rotation curve decomposition of 1128 disk galaxies. Results. We probe possible sources of uncertainty in our Qb measurements: the assumed scale height and its radial variation, the influence of the spiral arms torques, the effect of non-stellar emission in the bar region, and the dilution of the bar forces by the dark matter halo (our models imply that only ~10% of the disks in our sample are maximal). We find that for early- and intermediate-type disks (â3 †TQb by about 10â15%, which is of the same order as the uncertainty associated with estimating the vertical scale height. The halo correction on Qb becomes important for later types, implying a reduction of ~20â25% for T = 7â10. Whether the halo correction is included or not, the mean Qb shows an increasing trend with T. However, the mean A2max decreases for lower mass late-type systems. These opposing trends are most likely related to the reduced force dilution by bulges when moving towards later type galaxies. Nevertheless, when treated separately, both the early- and late-type disk galaxies show a strong positive correlation between Qb and A2max. For spirals the mean Δ â 0.5 is nearly independent of T, but it drops among S0s (â0.2). The Qb and Δ show a relatively tight dependence, with only a slight difference between early and late disks. For spirals, all our bar strength indicators correlate with the bar length (scaled to isophotal size). Late-type bars are longer than previously found in the literature. The bar fraction shows a double-humped distribution in the Hubble sequence (~75% for Sab galaxies), with a local minimum at T = 4 (~40%), and it drops for Mâ âČ 109.5â10 Mâ. If we use bar identification methods based on Fourier decomposition or ellipse fitting instead of the morphological classification, the bar fraction decreases by ~30â50% for late-type systems with T â„ 5 and correlates with Mh/Mâ. Our Mh/Mâ ratios agree well with studies based on weak lensing analysis, abundance matching, and halo occupation distribution methods, under the assumption that the halo inside the optical disk contributes roughly a constant fraction of the total halo mass (~4%). Conclusions. We find possible evidence for the growth of bars within a Hubble time; as (1) bars in early-type galaxies show larger density amplitudes and disk-relative sizes than their intermediate-type counterparts; and (2) long bars are typically strong. We also observe two clearly distinct types of bars, between early- and intermediate-type galaxies (T</p
Hard X-Ray to Radio Multiwavelength SED Analysis of Local U/LIRGs in GOALS Sample with Self-consistent AGN Model Including Polar-dust Component
We conduct a hard X-ray to radio multiwavelength spectral energy distribution
(SED) decomposition for 57 local luminous and ultraluminous infrared galaxies
(U/LIRGs) observed with Nuclear Spectroscopic Telescope Array and/or
Swift/Burst Alert Telescope in GOALS (Armus et al. 2009) sample. We modify the
latest SED-fitting code X-CIGALE by implementing the infrared (IR) CLUMPY
model, allowing the multiwavelength study with the X-ray torus model (XCLUMPY)
self-consistently. Adopting the torus parameters obtained by the X-ray fitting
(Yamada et al. 2021), we estimate the properties of host galaxies, active
galactic nucleus (AGN) tori, and polar dust. The star formation rates (SFRs)
become larger with merger stage and most of them are above the main sequence.
The SFRs are correlated with radio luminosity, indicating starburst emission is
dominant in the radio band. Although polar-dust extinction is much smaller than
torus extinction, the UV-to-IR (mainly IR) polar dust luminosities are 2
times larger than the torus ones. The polar-dust temperature decreases while
the physical size, estimated by the temperature and dust sublimation radius,
increases with AGN luminosity from a few tens of parsec (early mergers) to
kiloparsec scales (late mergers), where the polar dust is likely the expanding
(i.e., evolving) dusty outflows. The comparison between SFRs and intrinsic AGN
luminosities suggests that the starbursts occur first and AGNs arise later, and
overall their growth rates follow the simultaneous coevolution relation that
can establish the local galaxy-SMBH mass relation. We confirm the coexistence
of intense starbursts, AGNs, and large-scale outflows in late mergers,
supporting a standard AGN feedback scenario.Comment: 84 pages (5 tables/29 figures in the main text and 8 tables/18
figures in the Appendix), accepted in ApJ
El lenguaje, una herramienta para aprender mediante el modelo de gestiĂłn Aprendizaje Invertido, un estudio de caso en alumnos de 5Âș de primaria.
Estudio cualitativo sobre la implementaciĂłn del Aprendizaje Invertido dando respuesta a ÂżCĂłmo se implementa e impacta el Aprendizaje Invertido en el desarrollo de la competencia comunicativa: emplear el lenguaje como instrumento para aprender? A travĂ©s de una estrategia de innovaciĂłn basada en evidencia al aplicar el modelo de estudio de casos. Se obtuvieron los resultados a partir de la triangulaciĂłn de la informaciĂłn generada de la observaciĂłn activa y  la entrevista estructurada a docentes y  alumnos. Encontrando que la implementaciĂłn del modelo construye ambientes de aprendizaje activos donde se abarcan los diferentes estilos de aprendizaje y el uso de las TIC, logrando impactar en el rol del alumno, en el desarrollo de competencias y en el impulso del pensamiento crĂtico
Torus Constraints in ANEPD-CXO245: A Compton-thick AGN with Double-peaked Narrow Lines
We report on the torus constraints of the Compton-thick active galactic nucleus (AGN) with double-peaked optical narrow-line region emission lines, ANEPD-CXO245, at z = 0.449 in the AKARI NEP Deep Field. The unique infrared data on this field, including those from the nine-band photometry over 2â24 ÎŒm with the AKARI Infrared Camera, and the X-ray spectrum from Chandra allow us to constrain torus parameters such as the torus optical depth, X-ray absorbing column, torus angular width (Ï), and viewing angle (i). We analyze the X-ray spectrum as well as the UVâopticalâinfrared spectral energy distribution (UOI-SED) with clumpy torus models in X-ray (XCLUMPY) and infrared (CLUMPY), respectively. From our current data, the constraints on Ïâi from both X-rays and UOI show that the line of sight crosses the torus as expected for a type 2 AGN. We obtain a small X-ray scattering fraction (NH from the X-ray spectrum, we find that the gas-to-dust ratio is <4 times larger than the Galactic value
An Active Galactic Nucleus Recognition Model based on Deep Neural Network
To understand the cosmic accretion history of supermassive black holes, separating the radiation from active galactic nuclei (AGNs) and star-forming galaxies (SFGs) is critical. However, a reliable solution on photometrically recognising AGNs still remains unsolved. In this work, we present a novel AGN recognition method based on Deep Neural Network (Neural Net; NN). The main goals of this work are (i) to test if the AGN recognition problem in the North Ecliptic Pole Wide (NEPW) field could be solved by NN; (ii) to shows that NN exhibits an improvement in the performance compared with the traditional, standard spectral energy distribution (SED) fitting method in our testing samples; and (iii) to publicly release a reliable AGN/SFG catalogue to the astronomical community using the best available NEPW data, and propose a better method that helps future researchers plan an advanced NEPW database. Finally, according to our experimental result, the NN recognition accuracy is around 80.29% - 85.15%, with AGN completeness around 85.42% - 88.53% and SFG completeness around 81.17% - 85.09%
Study of the morphological features in the Spitzer Survey of Stellar Structure in Galaxies (SâŽG)
Abstract
Conspicuous morphological features such as rings, ringlenses, lenses, barlenses, and spiral arms are observed in many nearby disk galaxies. These features are believed to form due to the so-called secular evolution after the galaxies were formed, which means that their disks evolve in a more passive fashion and in longer timescales, compared to their formation processes. This slow evolution of disks is due to the effect of non-axisymmetric potentials, among which, a bar potential is perhaps the most effective of all. Strong rotating bars redistribute angular momentum and material through the disks of galaxies very effciently, and produce resonances. At these resonances the material is trapped and starts forming stars, creating beautiful rings. However, rings are not the only structure observed in disk galaxies. There are also spiral arms that, might or might not be created by bars. Other type of structures are lenses, which in images appear as flat light distributions with sharp edges, and ringlenses, whose appearance is intermediate between those of rings and lenses. Also, there are barlenses, which are conspicuous lens-like structures embedded in bars, and have been suggested to be the more face-on counterparts of Boxy/Peanut/X-shaped bulges. The study of the physical properties of all these structures provides a tool to investigate the mechanisms that create them and hence, to determine which are the processes that drive the slow evolution of galaxies.
In this thesis I study the morphological structures using mainly data from the Spitzer Survey of Stellar Structure in Galaxies (SâŽG), by means of their sizes, orientations, shapes and colors. The SâŽG contains images of ~ 2500 nearby galaxies of all Hubble types at 3.6 and 4.5 ÎŒm, allowing a dust free view of the old stellar population which is subject of the secular evolution.
Among the results presented in this thesis and the respective companion papers are the following. A catalog that contains the sizes, ellipticities and position angles of the morphological features in the SâŽG was created. This catalog also includes the measurements of the pitch angles of spiral arms. There is a corroboration of previous results showing that different types of morphological features appear in galaxies with different Hubble stages and bar families, and a confirmation of the resonant nature of rings but also of a high fraction of lenses and ringlenses. There is also an observation indicating that low mass galaxies lack nuclear structures such as nuclear rings due to the lack of inner Lindblad resonances caused by their low central mass concentrations. Observational evidence is presented indicating that a fraction of inner lenses in unbarred galaxies might be former barlenses of which the "thin bar" has probably dissolved or it is too faint to be detected.
The sizes of barlenses show a tight linear correlation with those of bars, being the size of the barlens typically half the size of the bar. The study of the optical colors of barlenses reveals their similarity with bars, giving observational evidence that their stellar populations are similar, and distinguishes them from disks and nuclear regions. The orientations of barlenses with respect to that of bars and disks reveal that barlenses are vertically thick structures. All these results support the idea that barlenses are the vertically thick inner parts of bars and hence relate them observationally to Boxy/Peanut/X-shaped bulges.
These results and others are published in a series of original papers in which I have collaborated and that are appended at the end of this work