10 research outputs found
New composite supernova remnant toward HESS J1844-030?
AIMS: HESS J1844-030 is a newly confirmed TeV source in the direction of the
X-ray pulsar wind nebula (PWN) candidate G29.4+0.1 and the complex radio source
G29.37+0.1, which is likely formed by the superposition of a background radio
galaxy and a Galactic supernova remnant (SNR). We investigate the possible
connection between the SNR, the PWN G29.4+0.1, and HESS J1844-030 to shed light
on the astrophysical origin of the TeV emission. METHODS: We performed an
imaging and spectral study of the X-ray emission from the PWN G29.4+0.1 using
archival observations obtained with the Chandra and XMM-Newton telescopes.
Public radio continuum and HI data were used to derive distance constraints for
the SNR that is linked to G29.37+0.1 and to investigate the interstellar medium
where it is expanding. We applied a simple model of the evolution of a PWN
inside an SNR to analyze the association between G29.4+0.1 and the radio
emission from G29.37+0.1. We compared the spectral properties of the system
with the population of TeV PWNe to investigate if HESS J1844-030 is the very
high energy counterpart of the X-ray PWN G29.4+0.1. RESULTS: We conclude that
G29.4+0.1 is a PWN and that a point source embedded on it is the powering
pulsar. The HI data revealed that the SNR linked to G29.37+0.1 is a Galactic
source at 6.5 kpc and expanding in a nonuniform medium. From the analysis of
the pulsar motion and the pressure balance at the boundary of X-ray emission,
we conclude that G29.4+0.1 could be a PWN that is located inside its host
remnant, forming a new composite SNR. Based on the magnetic field of the PWN
obtained from the X-ray luminosity, we found that the population of electrons
producing synchrotron radiation in the keV band can also produce IC photons in
the TeV band. This suggests that HESS J1844-030 could be the very high energy
counterpart of G29.4+0.1.Comment: Accepted for publication in A&A. The quality of some of the images
has been degraded. Abstract length has been reduce
An X-ray study of the supernova remnant G20.0-0.2 and its surroundings
Aims: We study the supernova remnant G20.0-0.2 and its surroundings in order
to look for the high energy counterpart of the radio nebula and to find
evidence of interaction between the shock front and the interstellar medium.
Methods: We used Chandra archival observations to analyze the X-ray emission
from the supernova remnant. The surrounding gas was investigated using data
extracted from the Galactic Ring Survey, the VLA Galactic Plane Survey, the
Galactic Legacy Infrared Midplane Survey Extraordinaire, and the Bolocam
Galactic Plane Survey. Results: G20.0-0.2 shows diffuse X-ray emission from the
central region of the radio remnant. Although the current data do not allow us
to distinguish between a thermal or non-thermal origin for the X-ray diffuse
emission, based on the radio properties we suggest a synchrotron origin as the
most favorable. The hard X-ray point source CXO J182807.4-113516 appears
located at the geometrical center of the remnant and is a potential candidate
to be the pulsar powering the nebula. We found a molecular cloud adjacent to
the flattest border of G20.0-0.2, indicating a probable interaction between the
shock front of the remnant and the molecular gas. Several young stellar object
candidates are found located in the brightest region of the molecular emission,
and over a millimeter continuum source and a dark cloud. This distribution is
an indication of an active star forming region around the supernova remnant.Comment: 13 pages, 10 figures, accepted for publication in A&A. Figures
degraded to reduce file siz
Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292
Aims. The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive young stellar object, was observed in molecular lines with the aim of discovering and studying molecular outflows.
Methods. We mapped a region of 3′× 3′ centred at MSXG34 using the Atacama Submillimeter Telescope Experiment in the 12CO J = 3–2 and HCO+J = 4–3 lines with an angular and spectral resolution of 22′′ and 0.11 km s-1. Additionally, public 13CO J = 1–0 and near-IR UKIDSS data obtained from the Galactic Ring Survey and the WFCAM Sciencie Archive were analysed.
Results. We found that the 12CO spectra towards the YSO present a self-absorption dip, as is common in star-forming regions, and spectral wings that indicate outflow activity. The HCO+ was detected only towards the MSXG34 position at vLSR ~ 14.2 km s-1, in coincidence with the 12CO absorption dip and approximately with the velocity of previous ammonia observations. HCO+ and NH3 are known to be enhanced in molecular outflows. When we analysed the spectral wings of the 12CO line, we discovered misaligned red- and blue-shifted molecular outflows associated with MSXG34. The near-IR emission shows a cone-like nebulosity composed of two arc-like features related to the YSO, which might be due to a cavity cleared in the circumstellar material by a precessing jet. This can explain the misalignment in the molecular outflows. From the analysis of the 13CO J = 1–0 data we suggest that the YSO is very likely related to a molecular clump ranging between 10 and 14 km s-1. This suggests that MSXG34, with an associated central velocity of about 14 km s-1, may be located in the background of this clump. Thus, the blue-shifted outflow is probably deflected by the interaction with dense gas along the line of sight. From a spectral energy distribution analysis of MSXG34 we found that its central object probably is an intermediate-mass protostar.Fil: Paron, Sergio Ariel. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Ortega, Martin Eduardo. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Petriella, Alberto. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Rubio, M.. Universidad de Chile. Facultad de Ciencias Fisicas y Matematicas; Chile. Universidad de Chile; Chil
A new study towards PSR J1826-1334 and PSR J1826-1256 in the region of HESS J1825-137 and HESS J1826-130
Aims. The goal of this paper is to detect synchrotron emission from the relic electrons of the crushed pulsar wind nebula (PWN) HESS J1825-137 and to investigate the origin of the γ-ray emission from HESS J1826-130. Methods. The study of HESS J1825-137 was carried out on the basis of new radio observations centred at the position of PSR J1826-1334 performed with the Karl G. Jansky Very Large Array at 1.4 GHz in configurations B and C. To investigate the nature of HESS J1826-130, we reprocessed unpublished archival data obtained with XMM-Newton. Results. The new radio continuum image towards PSR J1826-1334 reveals a bright radio source, with the pulsar located in its centre, which suggests that this feature could be the radio counterpart of the compact component of the PWN detected at high energy. The new 1.4 GHz radio data do not reveal emission with an extension comparable with that observed in γ-rays for the HESS J1825-137 source. On the other hand, the XMM-Newton study of the region including PSR J1826-1256 reveals an elongated non-thermal X-ray emitting nebula with the pulsar located in the northern border and a tail towards the peak of the very high energy source. The spectrum is characterized by a power law with a photon index going from 1.6 around the pulsar to 2.7 in the borders of the nebula, a behaviour consistent with synchrotron cooling of electrons. From our X-ray analysis we propose that HESS J1826-130 is likely produced by the PWN powered by PSR J1826-1256 via the inverse Compton mechanism.Fil: Duvidovich, Laura Patricia. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Giacani, Elsa Beatriz. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentina. Universidad de Buenos Aires. Facultad de Arquitectura, Diseño y Urbanismo; ArgentinaFil: Castelletti, Gabriela Marta. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Petriella, Alberto. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentina. Universidad de Buenos Aires. Ciclo Básico Común; ArgentinaFil: Supán, Jorge Leonardo. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentin
The southern molecular environment of SNR G18.8+0.3
In a previous paper we have investigated the molecular environment towardsthe eastern border of the SNR G18.8+0.3. Continuing with the study of thesurroundings of this SNR, in this work we focus on its southern border, whichin the radio continuum emission shows a very peculiar morphology with acorrugated corner and a very flattened southern flank. We observed two regionstowards the south of SNR G18.8+0.3 using the Atacama Submillimeter TelescopeExperiment (ASTE) in the 12CO J=3-2. One of these regions was also surveyed in13CO and C18O J=3-2. The angular and spectral resolution of these observationswere 22", and 0.11 km/s. We compared the CO emission to 20 cm radio continuummaps obtain as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS)and 870 um dust emission extracted from the APEX Telescope Large Area Survey ofthe Galaxy. We discovered a molecular feature with a good morphologicalcorrespondence with the SNR´s southernmost corner. In particular, there areindentations in the radio continuum map that are complemented by protrusions inthe molecular CO image, strongly suggesting that the SNR shock is interactingwith a molecular cloud. Towards this region we found that the 12CO peak is notcorrelated with the observed 13CO peaks, which are likely related to a nearby Hii region. Regarding the most flattened border of SNR G18.8+0.3, where aninteraction of the SNR with dense material was previously suggested, our 12COJ=3-2 map show no obvious indication that this is occurring.Fil: Paron, Sergio Ariel. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Celis Peña, Mariela Fernanda. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Ortega, Martin Eduardo. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Petriella, Alberto. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Rubio, M.. Universidad de Chile. Facultad de Ciencias Fisicas y Matematicas; ChileFil: Dubner, Gloria Mabel. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Giacani, Elsa Beatriz. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentin
The molecular environment of the pillar-like features in the H ii region G46.5–0.2
At the interface of HII regions and molecular gas, peculiar structuresappear, some of them with pillar-like shapes. Understanding their originis important for characterizing triggered star formation and the impactof massive stars on the interstellar medium. In order to study themolecular environment and influence of radiation on two pillar-likefeatures related to the H ii region G46.5-0.2, we performed molecularline observations with the Atacama Submillimeter Telescope Experimentand spectroscopic optical observations with the Isaac Newton Telescope.From the optical observations, we identified the star that is excitingthe H ii region as spectral type O4-6. The molecular data allowed us tostudy the structure of the pillars and an HCO+ cloud lyingbetween them. In this HCO+ cloud, which has no well-defined12CO counterpart, we found direct evidence of star formation:two molecular outflows and two associated near-IR nebulosities. Theoutflow axis orientation is perpendicular to the direction of theradiation flow from the HII region. Several Class I sources are alsoembedded in this HCO+ cloud, showing that it is usual thatyoung stellar objects (YSOs) form large associations occupying a cavitybounded by pillars. On the other hand, it was confirmed that theradiation-driven implosion (RDI) process is not occurring in one of thepillar tips.Fil: Paron, Sergio Ariel. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Celis Peña, Mariela Fernanda. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Ortega, Martin Eduardo. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Fariña, Cecilia Silvia. Isaac Newton Group Of Telescopes, Las Palmas, Iac; EspañaFil: Petriella, Alberto. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Rubio, M.. Departamento de AstronomÃa, Universidad de Chile; ChileFil: Ashley, R. P.. University Of Warwick; Reino Unid
Búsqueda de asociaciones entre candidatos a remanente de supernova y púlsares
El número de remanentes de supernova en la Galaxia es un tercio del total esperado. Se ha sugerido que esto podrÃa deberse a que no se detectan los remanentes más evolucionados, es decir, los menos brillantes en radio. Recientemente, el relevamiento GLOSTAR ha reportado 157 candidatos a remanente en el primer cuadrante Galáctico. En este trabajo, se estudia la asociación de estos candidatos con púlsares, con el objetivo de establecer su distancia. En base a criterios de posición, edad y velocidad de los púlsares, se hallaron 7 asociaciones. Se discuten métodos alternativos para estimar la distancia a los remanentes candidatos.El número de remanentes de supernova en la Galaxia es un tercio del total esperado. Se ha sugerido que esto podrÃa deberse a que no se detectan los remanentes más evolucionados, es decir, los menos brillantes en radio. Recientemente, el relevamiento GLOSTAR ha reportado 157 candidatos a remanente en el primer cuadrante Galáctico. En este trabajo, se estudia la asociación de estos candidatos con púlsares, con el objetivo de establecer su distancia. En base a criterios de posición, edad y velocidad de los púlsares, se hallaron 7 asociaciones. Se discuten métodos alternativos para estimar la distancia a los remanentes candidatos.Asociación Argentina de AstronomÃ
Radio study of the extended TeV source VER J1907+062
This paper aims to provide new insights on the origin of the TeV source VER J1907+062 through new high-quality radio observations. We used the Karl G. Jansky Very Large Array (VLA) to observe the whole extension of VER J1907+062 at 1.5 GHz with a mosaicking technique and the PSR J1907+0602 in a single pointing at 6 GHz. These data were used together with 12CO and atomic hydrogen observations obtained from public surveys to investigate the interstellar medium in the direction of VER J1907+062. The new radio observations do not show any evidence of a pulsar wind nebula (PWN) driven by the pulsars present in the field and no radio counterpart to the proposed X-ray PWN powered by PSR J1907+0602 is seen in the new VLA image at 6 GHz down to a noise level of 10 μJy beam-1. Molecular clouds were discovered over the eastern, southern, and western borders of the radio shell of G40.5-0.5, suggesting an association with this supernova remnant. We explored several scenarios for the origin of VER J1907+062. We propose as the most probable scenario one in which the TeV emission is produced by two separated γ-ray sources located at different distances: one of leptonic origin and associated with a PWN powered by PSR J1907+0602 at ∼3.2 kpc and another of hadronic origin and produced by the interaction between G40.5-0.5 and the surrounding molecular gas at ∼8.7 kpc.Fil: Duvidovich, Laura Patricia. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Petriella, Alberto. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentina. Universidad de Buenos Aires. Ciclo Básico Común; ArgentinaFil: Giacani, Elsa Beatriz. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentina. Universidad de Buenos Aires. Facultad de Arquitectura, Diseño y Urbanismo; Argentin
Study of the molecular and ionized gas in a possible precursor of an ultra-compact HII region
Aims. We study the molecular and the ionized gas in a possible precursor of an ultra-compact H ii region to contribute to the understanding of how high-mass stars build-up their masses once they have reached the zero-age main secuence.
Methods. We carried out molecular observations towards the position of the Red MSX source G052.9221−00.4892, using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the 12CO J=3−2, 13CO J=3−2, C18O J=3−2, and HCO+ J=4−3 lines with an angular resolution of about 22′′. We also present radio continuum observations at 6 GHz carried out with the Jansky Very Large Array (JVLA; USA) interferometer with a synthesized beam of 4 ′′.8× 4′′.1. The molecular data were used to study the distribution and kinematics of the molecular gas, while the radio continuum data were used to characterize the ionized gas in the region. Combining these observations with public infrared data allowed us to inquire about the nature of the source. Results. The analysis of the molecular observations reveals the presence of a kinetic temperature and H2 column density gradients
across the molecular clump in which the Red MSX source G052.9221−00.4892 is embedded, with the hotter and less dense gas in the inner region. The 12CO J=3−2 emission shows evidence of misaligned massive molecular outflows, with the blue lobe in positional coincidence with a jet-like feature seen at 8 µm. The radio continuum emission shows a slightly elongated compact radio source, with
a flux density of about 0.9 mJy, in positional coincidence with the Red MSX source. The polar-like morphology of this compact radio source perfectly matches the hourglass-like morphology exhibited by the source in the Ks−band. Moreover, the axes of symmetry of the radio source and the near-infrared nebula are perfectly aligned. Thus, based on the presence of molecular outflows, the slightly
elongated morphology of the compact radio source matching the hourglass-like morphology of the source at the Ks−band, and the lack of evidence of collimated jets in the near-infrared spectrum, one interpretation for the nature of the source, is that the Red MSX source G052.9221−00.4892 could be transiting a hyper-compact H ii region phase, in which the young central star emits winds and ionizing radiation through the poles. By the other hand, according to a comparison between the Brγ intensity and the radio flux density at 6 GHz, the source would be in a more evolved evolutionary stage of an optically thin UC H ii region in photoionization equilibrium. If this is the case, from the radio continuum emission, we can conjecture upon the spectral type of its exciting star which would be a B0.5V.Fil: Ortega, Martin Eduardo. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Paron, Sergio Ariel. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Giacani, Elsa Beatriz. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Celis Peña, Mariela Fernanda. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; ArgentinaFil: Rubio, M.. Universidad de Chile; ChileFil: Petriella, Alberto. Consejo Nacional de Investigaciónes CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de AstronomÃa y FÃsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomÃa y FÃsica del Espacio; Argentin