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Search Results: 1 - 10 of 593552 matches for " J. M. Torrelles "
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Modeling the Building Blocks of Water Masers in Cepheus A
L. Uscanga,J. Cantu00F3,S. Curiel,J. M. Torrelles
Revista mexicana de astronomía y astrofísica , 2003,
Abstract:
Water maser kinematics in massive star-forming regions: Cepheus A and W75N
J. M. Torrelles,N. A. Patel,S. Curiel,J. F. Gómez,G. Anglada,R. Estalella
Physics , 2012,
Abstract: VLBI multi-epoch water maser observations are a powerful tool to study the dense, warm shocked gas very close to massive protostars. The very high-angular resolution of these observations allow us to measure the proper motions of the masers in a few weeks, and together with the radial velocity, to determine their full kinematics. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N, among them: (i) the identification of different centers of high-mass star formation activity at scales of 100 AU; (ii) the discovery of new phenomena associated with the early stages of high-mass protostellar evolution (e.g., isotropic gas ejections); and (iii) the identification of the simultaneous presence of a wide-angle outflow and a highly collimated jet in the massive object Cep A HW2, similar to what is observed in some low-mass protostars. Some of the implications of these results in the study of high-mass star formation are discussed.
Not a galaxy: IRAS 04186+5143, a new young stellar cluster in the outer Galaxy
J. L. Yun,D. Elia,A. A. Djupvik,J. M. Torrelles,S. Molinari
Physics , 2015, DOI: 10.1093/mnras/stv1431
Abstract: We report the discovery of a new young stellar cluster in the outer Galaxy located at the position of an IRAS PSC source that has been previously mis-identified as an external galaxy. The cluster is seen in our near-infrared imaging towards IRAS 04186+5143 and in archive Spitzer images confirming the young stellar nature of the sources detected. There is also evidence of sub-clustering seen in the spatial distributions of young stars and of gas and dust. Near- and mid-infrared photometry indicates that the stars exhibit colours compatible with reddening by interstellar and circumstellar dust and are likely to be low- and intermediate-mass YSOs with a large proportion of Class I YSOs. Ammonia and CO lines were detected, with the CO emission well centred near the position of the richest part of the cluster. The velocity of the CO and NH$_3$ lines indicates that the gas is Galactic and located at a distance of about 5.5 kpc, in the outer Galaxy. Herschel data of this region characterise the dust environment of this molecular cloud core where the young cluster is embedded. We derive masses, luminosities and temperatures of the molecular clumps where the young stars reside and discuss their evolutionary stages.
Radio Observations of Disks and Jets in Young, Close Binary Systems
G. Anglada,L. F. Rodru00EDguez,J. M. Torrelles,R. Estalella
Revista mexicana de astronomía y astrofísica , 2003,
Abstract:
A bright radio HH object with large proper motions in the massive star-forming region W75N
C. Carrasco-Gonzalez,L. F. Rodriguez,J. M. Torrelles,G. Anglada,O. Gonzalez-Martin
Physics , 2010, DOI: 10.1088/0004-6256/139/6/2433
Abstract: We analyze radio continuum and line observations from the archives of the Very Large Array, as well as X-ray observations from the \emph{Chandra} archive of the region of massive star formation W75N. Five radio continuum sources are detected: VLA 1, VLA 2, VLA 3, Bc, and VLA 4. VLA 3 appears to be a radio jet; we detect J=1-0, v=0 SiO emission towards it, probably tracing the inner parts of a molecular outflow. The radio continuum source Bc, previously believed to be tracing an independent star, is found to exhibit important changes in total flux density, morphology, and position. These results suggest that source Bc is actually a radio Herbig-Haro object, one of the brightest known, powered by the VLA~3 jet source. VLA 4 is a new radio continuum component, located a few arcsec to the south of the group of previously known radio sources. Strong and broad (1,1) and (2,2) ammonia emission is detected from the region containing the radio sources VLA~1, VLA~2, and VLA~3. Finally, the 2-10 keV emission seen in the \emph{Chandra}/ACIS image shows two regions that could be the termination shocks of the outflows from the multiple sources observed in W75N.
Multiplicity, Disks and Jets in the NGC 2071 Star-Forming Region
C. Carrasco-Gonzalez,M. Osorio,G. Anglada,P. D'Alessio,L. F. Rodriguez,J. F. Gomez,J. M. Torrelles
Physics , 2011, DOI: 10.1088/0004-637X/746/1/71
Abstract: We present centimeter and millimeter observations of the NGC 2071 star-forming region performed with the VLA and CARMA. We detected counterparts at 3.6 cm and 3 mm for the previously known sources IRS 1, IRS 2, IRS 3, and VLA 1. All these sources show SEDs dominated by free-free thermal emission at cm wavelengths, and thermal dust emission at mm wavelengths, suggesting that all of them are associated with YSOs. IRS 1 shows a complex morphology at 3.6 cm, with changes in the direction of its elongation. We discuss two possible explanations to this morphology: the result of changes in the direction of a jet due to interactions with a dense ambient medium, or that we are actually observing the superposition of two jets arising from two components of a binary system. Higher angular resolution observations at 1.3 cm support the second possibility, since a double source is inferred at this wavelength. IRS 3 shows a clear jet-like morphology at 3.6 cm. Over a time-span of four years, we observed changes in the morphology of this source that we interpret as due to ejection of ionized material in a jet. The emission at 3 mm of IRS 3 is angularly resolved, with a deconvolved size (FWHM) of ~120 AU, and seems to be tracing a dusty circumstellar disk perpendicular to the radio jet. An irradiated accretion disk model around an intermediate-mass YSO can account for the observed SED and spatial intensity profile at 3 mm, supporting this interpretation.
Proper motions in cepheus a
L. F. Rodru00EDguez,J. M. Torrelles,A. C. Raga,J. Cantu00F3
Revista mexicana de astronomía y astrofísica , 2005,
Abstract: Presentamos un análisis de observaciones de radiocontinuo hechas con el Very Large Array hacia la región de formación estelar masiva Cefeo A. El propósito principal de este análisis es buscar y estudiar movimientos propios en las fuentes de radio a lo largo de las dos décadas de tiempo cubiertas por las observaciones. Las cuatro componentes de la fuente W, ubicada en la parte occidental de Cefeo A, muestran claros movimientos hacia el oeste con velocidades en el intervalo de 120 a 280 km s 1. Creemos que estas componentes están siendo excitadas por el chorro térmico Cep A HW3d, ubicado hacia el este de ellas. Más aún, proponemos que, después de ser deflectado en la posición de la fuente W, el chorro Cep A HW3d se mueve hacia el noroeste y produce la fuente óptica GGD 37. La fuente Cep A HW7 muestra un complejo patrón de movimientos propios para los que se discuten varias posibles explicaciones.
An Enigmatic, Expanding, Spherical Bubble Ejected from a Young Stellar Object
J. M. Torrelles,N. A. Patel,J. F. Gu00F3mez,P. T. P. Ho
Revista mexicana de astronomía y astrofísica , 2003,
Abstract:
Water maser detections in southern candidates to post-AGB stars and Planetary Nebulae
O. Suárez,J. F. Gómez,L. F. Miranda,J. M. Torrelles,Y. Gómez,G. Anglada,O. Morata
Physics , 2009, DOI: 10.1051/0004-6361/200911777
Abstract: We intended to study the incidence and characteristics of water masers in the envelopes of stars in the post-AGB and PN evolutionary stages. We have used the 64-m antenna in Parkes (Australia) to search for water maser emission at 22 GHz, towards a sample of 74 sources with IRAS colours characteristic of post-AGB stars and PNe, at declination $< -32 \deg$. In our sample, 39% of the sources are PNe or PNe candidates, and 50% are post-AGB stars or post-AGB candidates. We have detected four new water masers, all of them in optically obscured sources: three in PNe candidates (IRAS 12405-6219, IRAS 15103-5754, and IRAS 16333-4807); and one in a post-AGB candidate (IRAS 13500-6106). The PN candidate IRAS 15103-5754 has water fountain characteristics, and it could be the first PN of this class found. We confirm the tendency suggested in Paper I that the presence of water masers in the post-AGB phase is favoured in obscured sources with massive envelopes. We propose an evolutionary scenario for water masers in the post-AGB and PNe stages, in which ``water fountain'' masers could develop during post-AGB and early PN stages. Later PNe would show lower velocity maser emission, both along jets and close to the central objects, with only the central masers remaining in more evolved PNe.
Radio monitoring of NGC 7469: Late time radio evolution of SN 2000ft and the circumnuclear starburst in NGC 7469
M. A. Perez-Torres,A. Alberdi,L. Colina,J. M. Torrelles,N. Panagia,A. Wilson,E. Kankare,S. Mattila
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15389.x
Abstract: We present the results of an eight-year long monitoring of the radio emission from the Luminous Infrared Galaxy (LIRG) NGC 7469, using 8.4 GHz Very Large Array (VLA) observations at 0.3'' resolution. Our monitoring shows that the late time evolution of the radio supernova SN 2000ft follows a decline very similar to that displayed at earlier times of its optically thin phase. The late time radio emission of SN 2000ft is therefore still being powered by its interaction with the presupernova stellar wind, and not with the interstellar medium (ISM). Indeed, the ram pressure of the presupernova wind is \rho_w v_w^2 \approx 7.6E-9 dyn/cm^2, at a supernova age of approximately 2127 days, which is significantly larger than the expected pressure of the ISM around SN 2000ft. At this age, the SN shock has reached a distance r_{sh \approx 0.06 pc, and our observations are probing the interaction of the SN with dense material that was ejected by the presupernova star about 5820 years prior to its explosion. From our VLA monitoring, we estimate that the swept-up mass by the supernova shock after about six years of expansion is \approx 0.29 M_sun, assuming an average expansion speed of the supernova of 10000 km/s. We also searched for recently exploded core-collapse supernovae in our VLA images. Apart from SN 2000ft (S_\nu \approx 1760 microJy at its peak, corresponding to 1.1E28 erg/s/Hz, we found no evidence for any other radio supernova (RSN) more luminous than \approx 6.0E26 erg/s/Hz, which suggests that no other Type IIn SN has exploded since 2000 in the circumnuclear starburst of NGC 7469.
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