RevMexAA: Abstracts of Accepted Papers for Volume 46 Number 1


February 16, 2010

2010: February January

2009: December November October September



February 2010



HH jets aligned perpendicular to elephant trunks

A. C. Raga,1 V. Lora,2 and N. Smith3

1Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico
2Instituto de Astronomía, Universidad Nacional Autónoma de México,Mexico
3Department of Astronomy, University of California, Berkeley, USA

raga@nucleares.unam.mx

Received: 2010 January 11
Accepted: 2010 February 15


Abstract: We consider a system of outflows ejected from low mass young stars embedded in the tips of elephant trunks. We assume that these outflows have axes which are intrinsically perpendicular to the axes of the host elephant trunks. We then derive the distribution function expected for the angle between the projections of the outflow and elephant trunk axes on the plane of the sky. These distribution functions are useful for interpreting the alignments (or lack thereof) observed between HH outflow and elephant trunk axes in photoionized regions.



Planetary nebulae in the inner Milky Way: new abundances

O. Cavichia, R. D. D. Costa, and W. J. Maciel

Instituto de Astronomia, Geofísica e Ciências Atmosféricas Universidade de São Paulo, Brazil

cavichia@astro.iag.usp.br

Received: 2009 November 19
Accepted: 2010 February 8


Abstract: The study of planetary nebulae in the inner-disk and bulge gives important information on the chemical abundances of elements such as He, N, O, Ar, Ne, and on the evolution of these abundances, which is associated with the evolution of intermediate-mass stars and the chemical evolution of the Galaxy.
We present accurate abundances of the elements He, N, S, O, Ar, and Ne for a sample of 54 planetary nebulae located towards the bulge of the Galaxy, for which 33 have the abundances derived for the first time. The abundances are derived based on observations in the optical domain made at the National Laboratory for Astrophysics (LNA, Brazil). The data show a good agreement with other results in the literature, in the sense that the distribution of the abundances is similar to those works.



A Compact Radio Counterpart to the Energetic X-ray Pulsar Associated with the TeV Gamma-Ray Source J1813-178

S. Dzib, L. F. Rodríguez, and L. Loinard

Centro de Radioastronomía y Astrofísica, UNAM, Morelia, Mexico

s.dzib@crya.unam.mx

Received: 2009 November 4
Accepted: 2010 February 4


Abstract: We report the detection of a time-variable, compact radio source coincident with CXOU J181335.1-174957, the X-ray pulsar near the center of the young radio supernova remnant G12.82-0.02, which overlaps the compact TeV source HESS J1813-178. The compact radio source, named VLA J181335.1-174957, was detected in 4.86 GHz VLA observations made in 2006. New VLA observations made in 2009 do not detect the source at a level 1.90.7 times (2.8-s) lower than that of 2006. We suggest that VLA J181335.1-174957 may be related to one of the recently detected classes of variable radio pulsars but cannot reach a firmer conclusion.




January 2010



Amplitude fluctuations in curvature sensing: comparison of two schemes

V. V. Voitsekhovich and V. G. Orlov

Instituto de Astronomía, Universidad Nacional Autónoma de México,Mexico

voisteko@astroscu.unam.mx

Received: 2009 March 30
Accepted: 2010 January 14


Abstract: The influence of amplitude fluctuations on the quality of phase reconstruction in curvature sensing is investigated. The two curvature schemes are compared: with the two symmetrically-defocused images (Roddier scheme) and with a single defocused image (Nickson scheme). It is shown that the accuracy of phase reconstruction with the Nickson scheme is affected strongly even by a low-level amplitude fluctuations while the Roddier one works well under a quite strong amplitude fluctuations.



On the origin of the tailward velocity of O+ ions over themagnetic poles of Mars

M. Reyes-Ruiz,1 H. Aceves,1 and H. Perez-de-Tejada2

1Instituto de Astronomía, UNAM, Ensenada, México
2Instituto de Geofísica, UNAM, México, D.F., México

maurey@astrosen.unam.mx

Received: 2009 August 17
Accepted: 2010 January 11


Abstract: We numerically simulate the dynamics of a population of O+ ions of ionospheric origin picked-up by the solar wind in the dayside ionosheath of Mars. Their average velocity as they reach the magnetic polar regions of the planet is compared with in situ measurements of the Mars Express spacecraft. We find that the velocity of O+ ions measured over the magnetic poles of the planet, which is essentially tailward with very small y and z-components according to measurements, can not be solely accounted for in terms of particle gyromotions. We suggest that the velocity of O+ ions over the magnetic poles of the planet is more probably the result of wave-particle interactions that mediate the transfer of momentum from the solar wind plasma to ionospheric plasma and newly born ions in the ionosheath.



A geometrical model for the catalogs of galaxies

L. Zaninetti

Dipartimento di Fisica Generale
Universita degli Studi di Torino, Italy

zaninetti@ph.unito.it

Received: 2009 May 7
Accepted: 2010 January 6


Abstract: The 3D network originated by the faces of irregular Poissonian Voronoi Polyhedrons may represent the backbone on which the galaxies are originated. As a consequence the spatial appearance of the catalogs of galaxies can be reproduced. The selected catalogs to simulate are the 2dF Galaxy Redshift Survey and the Third Reference Catalog of Bright Galaxies. In order to explain the number of observed galaxies for a given flux/magnitude as a function of the redshift, the photometric properties of the galaxies should be carefully examined from both the astronomical and theoretical point of view. The statistics of the Voronoi normalized volume is modeled by two distributions and the Eridanus super-void is identified as the largest volume belonging to the Voronoi Polyhedron. The behavior of the correlation function for galaxies is simulated by adopting the framework of thick faces of Voronoi Polyhedrons on short scales, while adopting standard arguments on large scales.




December 2009


Age Estimation And Mass Functions of TTauri Stars
in Taurus Auriga Molecular Cloud

I  . Küçük and I  . Akkaya

Department of Astronomy and Space Sciences
Erciyes University, Turkey

kucuk@erciyes.edu.tr

Received: 2009 July 10
Accepted: 2009 December 14


Abstract: In this work the Present Day Mass Functions (PDMF) of T-Tauri Stars (TTS) which are in the Pre-Main Sequence (PMS) evolutionary phase of their evolution in Taurus-Auriga Molecular Cloud Complex have been calculated. For this purpose, by applying our modified Stellar Evolutionary Code, stellar models in the mass range 0.1 - 2 .5 M o. are used to determine the mass and age mass of TTS. The obtained mass function is compared with mass function of Miller & Scalo (1979). The age found for TTS is around 1 - 3 106 yr and mass function is about 0.644 0.348. From these results, we have calculated the stellar birthrate as about 1.3 10- 7 M o.  yr -1 in this region, that is to be considered.




November 2009


The green potential of the San Pedro Mártir observatory

J. Bohigas and J. M. Núñez

Instituto de Astronomía
Universidad Nacional Autónoma de México, Ensenada, Mexico

jbb@astrosen.unam.mx

Received: 2009 September 17
Accepted: 2009 November 23


Abstract: Weather observations carried out between October 2004 and July 2008 at the Mexican Observatorio Astronómico Nacional (OAN) are analyzed. Humidity in April, May and June was less than 55% nearly 90% of the time. Wind speed was larger at nightime and tended to decrease between March and November, and typical temperature variations during the night, for the entire day and for a whole year were about 2, 6 and 16oC respectively. The scale height or roughness length for the function relating wind speed and height above ground is 0.32. Normal activities associated to OAN produced somewhat more than 750 tones of CO2eq a year, roughly 3 times more than a typical mid-scale industry in the district of Ensenada, where OAN is located. Wind energy could have been extracted to produce electricity ~ 60% of the time, being more bountiful during the night and in the winter and early spring months. Solar and wind energy seem plentiful enough to supply the entire energy needs of the observatory, some 110 kWh including transportation.



Photoevaporation of a binary proplyd system

M. J. Vasconcelos,1 A. H. Cerqueira,1 A. C. Raga,2 and R. R. Amorim3

1LATO-DCET, Universidade Estadual de Santa Cruz, Ilhéus Bahia, Brazil
2Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico
3Instituto Nacional de Pesquisas Espaciais, São José dos Campos, São Paulo, Brazil

mjvasc@uesc.br

Received: 2009 September 21
Accepted: 2009 November 17


Abstract: We present 3D numerical simulations of photo-evaporation of a binary accretion disk system inside an H II region. The simulations take into account far- and extreme-ultraviolet (FUV and EUV) radiation from a stellar source. We study both FUV dominated and EUV dominated models. FUV dominated models show a well defined interproplyd shell in both Ha emission and density maps, when the separation of the binary system is relatively large (~ 2 000 AU). For smaller separations ( -~ 200 AU), the interproplyd shell no longer develops. We show that an EUV model with a suitable choice of parameters increases the Ha emission of the interproplyd shell relative to the emission of the ionization fronts, in better agreement with the observations of the binary proplyd LV1.



Herbig-Haro objects around CG 30

P. Kajdic  ,1,2 B. Reipurth,3 A. C. Raga,4 and J. Walawender3

1Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico
2Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
3Institute for Astronomy, University of Hawaii, USA
4Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico

primoz@geofisica.unam.mx

Received: 2009 August 6
Accepted: 2009 November 5


Abstract: In this work we study Herbig-Haro objects located in the region around the head of the cometary globule CG 30. Two sets of optical images are presented. The first set was obtained with the 3.5 m New Technology Telescope in 1995 in three emission lines: Ha, [SII]cc6731,6716  and [OII]c3729 . The second set is an Ha image of the CG 30/31/38 complex obtained in 2006 with the 8 m Subaru telescope. A proper motion study of the HH objects in the region was performed using the Ha images from both epochs. Due to the high resolution of our images we were able to, for the first time, resolve the HH 120 object into ten knots and measure proper motions for some of them. We discovered several new HH objects which are best seen in our [SII] image as well as a large bipolar jet, HH 950, emerging from the head of CG 30. We suggest that two previously known submillimeter sources are the driving sources for the HH 120 and HH 950 flows. They could both be binary sources, because (1) the proper motion vectors of the HH 120 knots suggest that this object is actually composed of two outflows and (2) the structure of the HH 950 flow suggests that the direction of the jet axis has changed in the past.



On the Precursors of Fossil Groups

Hrant Tovmassian

Instituto Nacional de Astrofísica, Óptica y Electrónica, Puebla, Mexico

hrant@inaoep.mx

Received: 2009 August 25
Accepted: 2009 November 4


Abstract: We compare the absolute magnitudes in K-band of the brightest galaxies in clusters of Bautz-Morgan type I with that of the fossil group brightest galaxies. It is found that brightest galaxies in fossil groups are on average fainter than the brightest galaxies in clusters. It is also shown that the brightness of the brightest galaxy depends on the cluster richness. It is concluded that the precursors of fossil groups were on average poor clusters.




October 2009



A Photometric and Spectroscopic Evaluation of the Site at Tonantzintla Observatory

H. M. Hernández-Toledo,1 L. A. Martínez-Vázquez,1 M. A. Moreno-Corral,2 and A. Pani-Cielo,3

1Instituto de Astronomía, Universidad Nacional Autónoma de México, D. F., Mexico
2Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, B. C., Mexico
3Instituto de Astronomía, Universidad Nacional Autónoma de México, Tonantzintla, Puebla, Mexico

(hector@astroscu.unam.mx

Received: 2009 March 24
Accepted: 2009 October 15


Abstract: Based on data obtained during various observing campaigns at the Observatorio Astronómico Nacional, Tonantzintla, an evaluation of the quality of the local sky is presented, and at the same time, the operability of the current photometric and spectroscopic instrumentation attached to the 1-m telescope is reviewed. The evaluation was carried out through an absolute CCD calibration to a set of standard stars in the field of the M67 star cluster in the B, V , R and I Johnson-Cousins photometric system and from Boller & Chivens long-slit spectroscopic observations of the local sky at various elevations. The sky brightness was estimated from our CCD frames and from a first visual campaign implemented in a local area of ~ 8km2 around the observatory yielding a mean sky surface brightness of 18.5 0.6 mag arcsec-2. The mean atmospheric extinction curve was also estimated, its behavior lying between the normal extinction and that related to volcanic outbursts. Compelling evidence relating that behavior to the activity of the nearby Popocatépetl volcano is presented. From the long-slit spectra of the sky at OAN-Tonantzintla, HgI Mercury lamp lines and NaI Sodium lines either of high and low pressure (HPS and LPS) lamps were identified. Comments on plausible astronomical projects under reasonable weather conditions and observing strategies as well as useful recommendations to improve on the current observing efficiency are provided. These results are relevant to providing support for the actual major upgrading of the observatory in terms of converting the OAN-Tonantzintla in the Laboratory for Astronomy Education at UNAM and eventually in a National Facility for Astronomy Education for the center-south part of the country.




September 2009



IMF from infrared photometry of young stellar clusters in Taurus-Auriga and Orion

Luis Salas and Irene Cruz-González

Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico

salas@astrosen.unam.mx

Received: 2009 June 8
Accepted: 2009 September 28


Abstract: We applied the extinction-disk-principal vectors approach to near infrared photometric data of the Taurus-Auriga region and Orion Nebula young stellar clusters. By assuming that the cluster age is represented by the median value of the age distribution we are able to derive the distribution of stellar masses. We showed that the resulting initial mass function (IMF) for these two young stellar clusters compares remarkably well and might be a robust representation of the IMF obtained by spectroscopic or photometric methods. The method also yields extinction and disk contribution for each star. The overall extinction distribution for the Orion cluster is analyzed and compares well with previous work. The frequency of T Tauri stars with disks is dominant.



H91a Radio Recombination Line and 3.5 cm Continuum Observations of the Planetary Nebula NGC 3242

L. F. Rodríguez,1 Y. Gómez,1 J. Alberto López,2 Ma. Teresa García-Díaz,2 and David M. Clark2

1Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia, Mexico
2Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Mexico

l.rodriguez@crya.unam.mx

Received: 2009 August 25
Accepted: 2009 September 25


Abstract: We present high sensitivity H91a and 3.5 cm radio continuum observations toward the planetary nebula NGC 3242. The electron temperature determined assuming local thermodynamic equilibrium is consistent within ~10% with that derived from optical lines and the Balmer discontinuity. The line emission and the continuum emission have very similar spatial distribution, suggesting that at this wavelength there is no other continuum process present in a significant manner. In particular, we conclude that emission from spinning dust is not important at this wavelength. In this radio recombination line the nebula presents a radial velocity structure consistent with that obtained from observations of optical lines.



SIMPLE MODEL WITH TIME-VARYING FINE-STRUCTURE ”CONSTANT” - PART II

M. S. Berman

Instituto Albert Einstein, Curitiba, PR, Brazil

msberman@institutoalberteinstein.org

Received: 2009 June 22
Accepted: 2009 September 1


Abstract: The extension of Dirac’s LNH to cover cosmological and fine-structure time-varying “constants”, and the rotation of the Universe, is here analysed, including a “derivation” of the angular speed of the present Universe, and of the inflationary phase. Criticizable points on the present calculation, are clarified.



CCD Photometry of M15

A. Ruelas-Mayorga,1 L. J. Sánchez,1 G. Herrera,2 and A. Nigoche-Netro3

1Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico
2Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico
3Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain

rarm@astroscu.unam.mx

Received: 2009 January 9
Accepted: 2009 September 1


Abstract: We present CCD observations of the galactic globular cluster M15, in the B and V filters. The cluster was reasonably covered, except in its northern region where our observations present a gap. We obtained a Hertszprung-Russell (HR) diagram for each region observed, and later we produced a combined HR diagram containing more than 3000 stars. We generate a clean Colour Magnitude Diagram (CMD) and a Super Fiducial Line (SFL). Application of several methods and isochrone fitting leads us to obtain values for the metallicity [Fe/H]M15 ~-2.16 0.10, the reddening E(B - V )M15 ~ 0.11 0.03, and a distance modulus of [(m - M)0]M15 ~ 15.03.