INAOE | Astrofísica | Seminarios
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2018-08-31 Extreme quasars at high redshift
Area: Astrofísica
Investigador Invitado Mary Loli Martinez Aldama
Filiación Institucional IAA-Granada, España
Resumen: Ver resumen The study of the AGN accreting close to the Eddington limit (L/LEdd~1) has taken an important role, due to their potential use as standard candles for cosmological applications. With the purpose to understand the physics of extreme quasar, we perform a spectroscopic analysis of a sample of highly accreting quasars at high redshift (z~2–3). Our sample were observed with the OSIRIS spectrograph on the GTC 10.4 m telescope located at the Observatorio del Roque de los Muchachos in La Palma. The highly accreting quasars were identified using the 4D Eigenvector 1 formalism, which is able to organize type 1 quasars over a broad range of redshift and luminosity. The kinematic and physical properties of the broad line region have been derived by fitting the profiles of strong UV emission lines such as AlIII λ1860, SiIII]λ1892 and CIII]λ1909. We find that AlIIIλ1860 can be associated with a low-ionization virialized sub-system. xA sources show strong blueshifts in the high-ionization lines like in CIVλ1549, indicating a relation between the high Eddington ratios and the productions of outflows. The extreme radiative properties of highly accreting quasar make them prime candidates for maximum feedback effects on the host galaxy. The characterization of extreme quasar allow to assemble large samples of extreme quasars from the latest data releases of the SDSS, especially useful for deriving independent estimates of ΩM in the redshift range 1<z<3.5.
Lugar-Hora Auditorio del Centro de Información - 12:00
2018-10-19 Masa y espín del agujero negro de Kerr en términos de corrimientos al rojo
Area: Astrofísica
Investigador Invitado Alfredo Herrera Aguilar
Filiación Institucional IF-BUAP
Resumen: Ver resumen En esta charla presentaremos fórmulas analíticas relativistas para estimar la masa y el espín de un agujero negro de Kerr en términos del corrimiento al rojo/azul de fotones emitidos por estrellas que lo orbitan siguiendo trayectorias circulares estables sobre el plano ecuatorial (o galáctico, de ser el caso), así como del radio orbital de dichas estrellas. En principio, estas fórmulas se pueden aplicar a ciertos sistemas astrofísicos
que poseen la estructura antes descrita si se tienen los instrumentos y la precisión necesarias. En el nivel de nuestras modestas aportaciones, la retroalimentación con los astrónomos es de crucial importancia.
Lugar-Hora Auditorio del Centro de Información - 12:00
2018-11-14 A submillimeter background galaxy projected on the debris disk of  HD95086 revealed by ALMA
Area: Astrofísica
Investigador Invitado Luis Alberto Zapata González
Filiación Institucional IRYA-Morelia
Resumen: Ver resumen In this talk, I present sensitive observations carried out with the  Atacama Large Millimeter/Submillimeter Array (ALMA) of the dusty debris disc HD 95086. These observations were made in bands 6 (223 GHz) and 7 (338 GHz) with an angular resolution of about 1’’, which allowed us to resolve well the bright debris disc. However, we did not detect CO (J = 2-1) and (J = 3-2) emission, excluding the possibility of an evolved gaseous primordial disc. From the mm. emission, we computed a dust mass for the debris disc HD95086 of 0.5 earth masses, resulting in a dust-to-gas ratio of more than 50, which is typical for debris. Our observations additionally detected a of a strong submillimeter source to the north-west of the disc. This new  object might be interpreted as a planet in formation on the periphery of the debris disc HD 95086 or as a strong impact between dwarf planets. However, given the absence of the proper motions of the object similar to those reported in the debris disc (estimated from these new ALMA observations) and for the optical star, this is more likely to be a submillimeter background galaxy. I will discuss the possibilities of finding more background galaxies in the ALMA fields.
Lugar-Hora Auditorio del Centro de Información - 16:00
2018-11-16 La Astronomía Mexicana bajo la luz de indicadores internacionales
Area: Astrofísica
Investigador Invitado J. Jesús González
Filiación Institucional Instituto de Astronomía, UNAM
Resumen: Ver resumen La Astronomía se ha mantenido como la ciencia de mayor impacto y contribución internacional en nuestro país, algo sorprendente ya que México no ha participado proporcionalmente en los grandes consorcios e infraestructuras desarrolladas desde los años 90’s. Utilizando las herramientas de valoración científica, como el Word of Science, que utilizan las agencias y analistas internacionales en sus tomas de decisión,  presentamos un análisis de la producción e impacto de la Astrofísica Mexicana desde 1980. En este marco, al analizar también la astrofísica generada en UNAM, y en particular por el Instituto de Astronomía, estudiamos en mayor detalle puntos como segos en las citas y el factor de impacto como indicador de calidad. Finalmente, tocamos puntos relativos a la Revista Mexicana de Astronomía y Astrofísica.
Lugar-Hora Auditorio del Centro de Información - 13:00
2018-11-23 Comprehensive analysis of HD 105, a young Solar System analog
Area: Astrofísica
Investigador Invitado Jonathan Marshall
Filiación Institucional Institute of Astronomy and Astrophysics, Taipei
Resumen: Ver resumen HD 105 is a nearby, pre-main sequence G0 star hosting a moderately bright debris disc (Ldust/Lstar ∼ 2.6×10^-4). The star and its surroundings might therefore be considered an analogue of the young Solar System. We refine
the stellar parameters based on an improved Gaia parallax distance, identify it as a pre-main sequence star with an age of 50 ± 16 Myr. The circumstellar disc was marginally resolved by Herschel/PACS imaging at far-infrared wavelengths. Here we present an archival ALMA observation at 1.3 mm, revealing the extent
and orientation of the disc. We also present HST/NICMOS and VLT/SPHERE 
near-infrared images, where we recover the disc in scattered light at the ≥ 5-σ level. This was achieved by employing a novel annular averaging technique, and is the first time this has been achieved for a disc in scattered light. Simultaneous modelling of the available photometry, disc architecture, and detection in scattered light allow better determination of the disc's architecture, and dust grain minimum size, composition, and albedo. We measure the dust albedo to lie between 0.19 and 0.06, the lower value being consistent with Edgeworth-Kuiper belt objects.
Lugar-Hora Auditorio del Centro de Información - 15:00
2018-12-07 Gravitational feedback in action: as the newborn stars disperse their parental gas, the gravity of the gas disperses the clusters
Area: Astrofísica
Investigador Invitado Manuel Zamora
Filiación Institucional INAOE
Resumen: Ver resumen Photodissociation bubbles are common features in the interstellar medium. They can be easily detected as ring-like structures in line emission maps tracing either neutral atomic or molecular hydrogen. One particularly clear case is in the Lambda-Ori region, which exhibits a quite symmetric, 20 pc radius ring that has been previously interpreted as to be the result of the expansion of a supernova explosion between ~1-2 Myr ago. Recently, high precision proper motions of stars in this region became available through the second data release of Gaia, which showed that the projected velocity vectors of Lambda-Ori stars tend clearly to point away from the center of the ring/bubble, as could be expected for an open cluster that it is breaking apart. Moreover, the data suggest that stars located farther from the center of the ring/bubble have faster (or larger) proper motions. This leads us to propose a different scenario for the formation of the Lambda-Ori bubble and its proper motions. We used numerical simulations to show that, while at the beginning, stellar clusters are formed in a collapsing environment and the stars are drawn to each other due to the gravity of the cloud, later the feedback from the newborn massive stars in these clusters expels the gas from the center, creating a cavity and moving the potential well away from the center of collapse. Since neither the formed shells nor the parental clouds are symmetric, a net force pulling out the stars is present, accelerating the stars towards the edges of the cavity. In this way, we propose that gravity from the expelled gas appears to be the crucial mechanism producing unbound clusters that expand away from their formation center. This mechanism has not been considered before, mainly because in previous simplified models the gravitational potential was usually one of an empty, homogeneous sphere, which is constant, and thus no net force is expected to act over the clusters embedded in a shell structure.
Lugar-Hora Auditorio del Centro de Información - 12:00

Última modificación :
05-07-2010 a las 14:08 por Webmaster

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