Y. Gómez

Universidad Nacional Autónoma de México, Ciudad de México, The Federal District, Mexico

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Publications (108)390.79 Total impact

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    ABSTRACT: We present 3D hydrodynamical simulations of an isotropic fast wind interacting with a previously ejected toroidally shaped slow wind in order to model both the observed morphology and kinematics of the planetary nebula (PN) NGC 6302 (so-called the Butterfly Nebula). This nebula is among the most complex ever observed in PNe. From our numerical simulations, we have obtained an intensity map for H alpha emission to make a comparison with the Hubble Space Telescope observations of this object. We have also simulated the proper-motions of nebular knots and contrast them with those measured by comparing two set of observations. We have found that based on a generalized interacting stellar wind model, the morphology as well as the Hubble-type expansion indicated by the proper-motion measurements are explained.
    03/2014;
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    ABSTRACT: A survey of the Milky Way disk and the Magellanic System at the wavelengths of the 21-cm atomic hydrogen (HI) line and three 18-cm lines of the OH molecule will be carried out with the Australian Square Kilometre Array Pathfinder telescope. The survey will study the distribution of HI emission and absorption with unprecedented angular and velocity resolution, as well as molecular line thermal emission, absorption, and maser lines. The area to be covered includes the Galactic plane (|b|< 10deg) at all declinations south of delta = +40deg, spanning longitudes 167deg through 360deg to 79deg at b=0deg, plus the entire area of the Magellanic Stream and Clouds, a total of 13,020 square degrees. The brightness temperature sensitivity will be very good, typically sigma_T ~ 1 K at resolution 30arcsec and 1 km/s. The survey has a wide spectrum of scientific goals, from studies of galaxy evolution to star formation, with particular contributions to understanding stellar wind kinematics, the thermal phases of the interstellar medium, the interaction between gas in the disk and halo, and the dynamical and thermal states of gas at various positions along the Magellanic Stream.
    Publications of the Astronomical Society of the Pacific 07/2012; · 3.69 Impact Factor
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    ABSTRACT: It has been suggested that the presence of disks or tori around the central stars of pre Planetary Nebulae and Planetary Nebulae is related to the collimation of the jet that are frequently observed in these sources. These disks or tori can be traced by the maser emission of some molecules such as water. In this work we present Very Large Array (VLA) observations of the water maser emission at 22 GHz toward the PN IRAS 18061-2505, for which the masers appear located on one side of the central star. For comparison with the observations, we present a simple kinematical model of a disk rotating and expanding around the central star. The model matches qualitatively the observations. However, since the masers appear only on one side of the disk, these results are not conclusive.
    Proceedings of the International Astronomical Union 07/2012; 8(S287):258-259.
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    ABSTRACT: We have studied the polarization characteristics and Faraday rotation of the extragalactic radio source J17204-3554, which appears projected on the north lobe of the Galactic H II region NGC 6334A. From observations made with the Very Large Array at 6.0 and 3.6 cm in three different epochs (1994, 1997 and 2006), we estimate a rotation measure of +5100 ± 900 rad m-2 for the extragalactic source. This large rotation measure implies a line-of-sight average magnetic field of B∥≃+ 36 ± 6 μG, the largest obtained by this method for an H II region. NGC 6334A is significantly denser than other H II regions studied and this larger magnetic field is expected on the grounds of magnetic flux conservation. The ratio of thermal to magnetic pressure is ˜5 in the range of values determined for more diffuse H II regions.
    Monthly Notices of the Royal Astronomical Society 02/2012; 420(1):279-282. · 5.52 Impact Factor
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    ABSTRACT: We have studied the polarization characteristics and Faraday rotation of the extragalactic radio source J17204$-$3554, that appears projected on the north lobe of the galactic H II region NGC 6334A. From observations made with the Very Large Array at 6.0 and 3.6 cm in three different epochs (1994, 1997, and 2006), we estimate a rotation measure of +5100$\pm$900 rad m$^{-2}$ for the extragalactic source. This large rotation measure implies a line-of-sight average magnetic field of $B_\parallel \simeq +36\pm6$ $\mu$G, the largest obtained by this method for an H II region. NGC 6334A is significantly denser than other H II regions studied and this larger magnetic field is expected on the grounds of magnetic flux conservation. The ratio of thermal to magnetic pressure is $\sim$5, in the range of values determined for more diffuse H II regions.
    10/2011;
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    ABSTRACT: Searching for molecular tracers of disks in massive star-formation regions is a complex task. There are molecules that show emission from the envelope and the disk simultaneously. Other molecules show optically thick emission, thus complicating the kinematic study of disks. On the other hand, S-bearing species (such as H2S, SO, SO2, CS, and OCS) could be intimately linked with the evaporation process of the disk surface becoming good tracers of the dynamics of the innermost parts of the high-mass protostars. Recently, several papers have been published on the detection of S-bearing species in disks and other warm gas structures of massive star-forming regions. In particular, SO2 transitions, ubiquitous within the (sub)millimeter range, show a very compact nature, suggesting their close association with circumstellar structures. We have carried out sub-arcsecond SMA observations towards the central region of the HH 80-81 system. The mm continuum emission shows two main sources, one of them located at the center of the extremely large (5.3 pc long) bipolar radio continuum jet observed in this region. The dust emission appears compact and coincides with a radio continuum source. Between the spectral lines detected (H2CO and SO), the SO2 line transitions show compact emission toward this source. These molecular lines clearly show a velocity gradient perpendicular to the radio jet axis. Both, the dust continuum and the molecular line emission suggest the existence of a rotating circumstellar disk around a massive protostar.
    10/2011;
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    ABSTRACT: In this work we present high angular resolution observation of the C110α radio recombination line (RRL) to study the photodissociated region (PDR) associated with the H II region of cometary morphology (VLA) in the GGD14 complex.
    10/2011;
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    ABSTRACT: New observations of the HI 21 cm line toward the cometary HII region G213.880-11.837 are presented. These observations, carried out with an angular resolution of 15'', reveal that the neutral gas in this region is part of an expanding flow. The analysis of the kinematics of the HI gas suggests that the HI gas is undergoing a champagne flow: based on the difference between the radial velocities of the neutral gas in the tail ( 4km s^{-1}) compared to the velocities of the ambient molecular gas ( 11.5 km s^{-1}) and the asymmetry of the HI emission. Besides this photodissociated region, there is only one other reported following an HI champagne flow (G111.61+0.37).
    10/2011;
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    ABSTRACT: We present several molecular line emission arcsec and subarcsec observations obtained with the Submillimeter Array (SMA) in the direction of the massive protostar IRAS 18162-2048, the exciting source of HH 80-81. The data clearly indicates the presence of a compact (radius~425-850 AU) SO2 structure, enveloping the more compact (radius~150 AU) 1.4 millimeter dust emission (reported in a previous paper). The emission spatially coincides with the position of the prominent thermal radio jet which terminates at the HH 80-81 and HH 80N Herbig-Haro objects. Furthermore, the molecular emission is elongated in the direction perpendicular to the axis of the thermal radio jet, suggesting a disk-like structure. We derive a total dynamic mass (disk-like structure and protostar) of 11-15 msun. The SO2 spectral line data also allow us to constrain the structure temperature between 120-160 K and the volume density > 2x10^9 cm-3. We also find that such a rotating flattened system could be unstable due to gravitational disturbances. The data from C17O line emission show a dense core within this star-forming region. Additionally, the H2CO and the SO emissions appear clumpy and trace the disk-like structure, a possible interaction between a molecular core and the outflows, and in part, the cavity walls excavated by the thermal radio jet.
    The Astronomical Journal 07/2011; 142(4). · 4.97 Impact Factor
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    ABSTRACT: In this paper, we report on high angular resolution radio observations of the planetary nebula NGC 6881 obtained with the Very Large Array at a wavelength of 6 cm. The emission appears to be the superposition of a roundish core and a point-symmetric bipolar structure elongated along a position angle of about 145$^\circ$. This is strongly reminiscent of the morphology seen in H$\alpha$ and [NII] images. A comparison between VLA observations obtained in 1984 and 1994 clearly reveals the expansion of the core of the nebula, at a rate of 2.1 $\pm$ 0.7 mas yr$^{-1}$. Assuming that the expansion velocity in the plane of the sky (determined from these measurements) and the expansion velocity along the line of sight (estimated from optical spectroscopy available in the literature) are equal, we find a distance to NGC 6881 of 1.6 $\pm$ 0.5 kpc $\pm$ 0.3 kpc, where the first error reflects the uncertainty on the expansion, and the second error comes from the potential difference between pattern and material speeds. This distance is compatible with (but does not necessarily imply) an association of NGC 6881 with the nearby HII region Sh 2-109 and, more generally, the Cygnus star-forming region.
    Monthly Notices of the Royal Astronomical Society 03/2011; 414. · 5.52 Impact Factor
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    ABSTRACT: In this paper we present the results of very long baseline interferometry (VLBI) ob- servations carried out with the VLBI Exploration of Radio Astrometry (VERA) array and the Very Long Baseline Array (VLBA) toward H2O masers in a young planetary nebula K 3-35. From the VERA observations we measured the annual parallax and proper mo- tion of a bright water maser spot in K 3-35. The resulting distance is D = 3.9+0.7 kpc. -0.5 This is the first time that the parallax of a planetary nebula is obtained by observations of its maser emission. On the other hand, the proper motion of K 3-35 as a whole was esti- mated to be {\mu}{\alpha} = -3.34+/-0.10 mas yr-1, {\mu}{\delta} = -5.93+/-0.07 mas yr-1. From these results we determined the position and velocity of K 3-35 in Galactic cylindrical coordinates: (R,{\theta},z) = (7.11+0.08-0.06 kpc, 27+/-5{\circ}, 140+25-18 pc) and (VR, V{\theta}, Vz) = (33+/-16, 233+/-11, 11+/-2) km s-1, respectively. Additionally, from our VLBA observations we measured the relative proper motions among the water maser spots located in the central region of the nebula, which have been proposed to be tracing a toroidal structure. The distribution and relative proper motions of the masers, compared with previous reported observed epochs, suggest that such structure could be totally destroyed within a few years, due to the action of high velocity winds and the expansion of the ionization front in the nebula.
    Publications- Astronomical Society of Japan 01/2011; 63. · 2.44 Impact Factor
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    ABSTRACT: In order to better understand the formation of asymmetric structures in planetary nebulae (PNe) we have studied two of the three planetary nebulae that are known to harbor water maser emission: K 3-35, IRAS 17347-3139. These objects show a clear bipolar morphology with a narrow waist; the water maser emission arises from the central region and in the case of K 3-35 it is also found located at the surprisingly large distance of 4000 AU from the central star (near the tips of the bipolar lobes). Several mechanisms have been proposed to explain the bipolar morphology of PNe. In the case of K 3-35 we believe that we may be observing some of them at the same time: (i) a disk-like structure traced by the H_{2}O masers, (ii) a precessing bipolar jet probably due to the presence of a binary companion and (iii) circular polarization in the OH 1665 MHz masers, which suggests the presence of a magnetic field. A detailed modeling of all these observational results might shed light on the formation of asymmetric structures in planetary nebula. On the other hand, we also present the first high angular resolution images of the ionized gas (in radio continuum at lambda= 1.3 and 0.7 cm) of IRAS 17347-3139. The results support the presence of a collimated wind which might be shaping the bipolar lobes. Additionally, the 0.7 cm images show an equatorial structure that has been interpreted as a high density ionized torus in which the water maser emission would be arising.
    01/2011;
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    ABSTRACT: The GGD27 complex includes the HH 80-81-80N system, which is one of the most powerful molecular outflows associated with a high mass star-forming region observed up to now. This outflow is powered by the star associated with the source IRAS 18162-2048. Here we report the detection of continuum emission at sub-arcsec/arcsec resolution with the Submillimeter Array at 1.36mm and 456microns, respectively. We detected dust emission arising from two compact cores, MM1 and MM2, separated by about 7" (~12000AU in projected distance). MM1 spatially coincides with the powerful thermal radio continuum jet that powers the very extended molecular outflow, while MM2 is associated with the protostar that drives the compact molecular outflow recently found in this region. High angular resolution obervations at 1.36mm show that MM1 is unresolved and that MM2 splits into two subcomponents separated by ~1". The mass of MM1 is about 4Msun and it has a size of <300AU. This is consistent with MM1 being associated with a massive and dense (n(H2)>10^9cm-3) circumstellar dusty disk surrounding a high-mass protostar, which has not developed yet a compact HII region. On the other hand, the masses of the two separate components of MM2 are about 2Msun each. One of these components is a compact core with an intermediate-mass young protostar inside and the other component is probably a pre-stellar core. MM1 is the brigthest source at 1.36mm, while MM2 dominates the emission at 456microns. These are the only (sub)millimeter sources detected in the SMA observations. Hence, it seems that both sources may contribute significantly to the bolometric luminosity of the region. Finally, we argue that the characteristics of these two sources indicate that MM2 is probably in an earlier evolutionary stage than MM1. Comment: Accepted in AJ (Oct 31, 2010)
    The Astronomical Journal 11/2010; · 4.97 Impact Factor
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    ABSTRACT: K 3-35 is a very young planetary nebula (PN) with a characteristic S-shaped radio emission morphology. It is the first PN where water vapor maser was detected: the emission is located in a torus-like structure with a radius of 100 AU and also at the surprisingly large distance of 5000 AU from the star, in the tips of the bipolar lobes. Several mechanism have been proposed to explain the bipolar morphology of PNe, and in the case of K 3-35 we believe we may be observing several of them at the same time: i) a disk-like structure traced by the H2O masers, ii) a precessing bipolar jet probably due to the presence of a binary companion and iii) circular polarization in the OH 1665 MHz masers, which suggests the presence of a magnetic field. Additional observations and modeling are needed to establish what mechanisms are shaping K 3-35.
    Proceedings of the International Astronomical Union 08/2010; 6:414 - 415.
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    ABSTRACT: We present high angular and spectral resolution H I 21 cm line observations toward the cometary-shaped compact H II region G213.880–11.837 in the GGD 14 complex. The kinematics and morphology of the photodissociated region, traced by the H I line emission, reveal that the neutral gas is part of an expanding flow. The kinematics of the H I gas along the major axis of G213.880–11.837 shows that the emission is very extended toward the SE direction, reaching local standard of rest (LSR) radial velocities in the tail of about 14 km s–1. The ambient LSR radial velocity of the molecular gas is 11.5 km s–1, which suggests a champagne flow of the H I gas. This is the second (after G111.61+0.37) cometary H II/H I region known.
    The Astronomical Journal 08/2010; 140(4):913. · 4.97 Impact Factor
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    ABSTRACT: We present high angular and spectral resolution HI 21~cm line observations toward the cometary-shaped compact HII region G213.880-11.837 in the GGD~14 complex.The kinematics and morphology of the photodissociated region, traced by the HI line emission, reveal that the neutral gas is part of an expanding flow. The kinematics of the HI gas along the major axis of G213.880-11.837 shows that the emission is very extended toward the SE direction, reaching LSR radial velocities in the tail of about 14 km/s. The ambient LSR radial velocity of the molecular gas is 11.5 km/s, which suggests a champagne flow of the HI gas. This is the second (after G111.61+0.37) cometary HII/HI region known. Comment: Accepted for publication in the Astronomical Journal (10 pages, 4 figures, 1 table)
    07/2010;
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    ABSTRACT: Using the Very Large Array (VLA) at 3.6~cm we identify four new compact radio sources in the vicinity of the cometary HII region G78.4+2.6 (VLA~1). The four compact radio sources (named VLA~2 to VLA~5), have near-infrared counterparts, as seen in the 3.6 $\mu$m Spitzer image. One of them (VLA~5) clearly shows evidence of radio variability in a timescale of hours. We explore the possibility that these radio sources are associated with pre-main sequence (PMS) stars in the vicinity of the UC HII region G78.4+2.6. Our results favor the smaller distance value of 1.7 kpc for G78.4+2.6. In addition to the detection of the radio sources in the vicinity of G78.4+2.6, we detected another group of five sources which appear located about 3' to the northwest of the HII region. Some of them exhibit extended emission. Comment: Accepted for publication in RevMexAA, vol. 46, 2010
    06/2010;
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    ABSTRACT: Cyg OB2 #5 is a contact binary system with variable radio continuum emission. This emission has a low-flux state where it is dominated by thermal emission from the ionized stellar wind and a high-flux state where an additional non-thermal component appears. The variations are now known to have a period of 6.7 +/- 0.2 yr. The non-thermal component has been attributed to different agents: an expanding envelope ejected periodically from the binary, emission from a wind-collision region, or a star with non-thermal emission in an eccentric orbit around the binary. The determination of the angular size of the non-thermal component is crucial to discriminate between these alternatives. We present the analysis of VLA archive observations made at 8.46 GHz in 1994 (low state) and 1996 (high state), that allow us to subtract the effect of the persistent thermal emission and to estimate an angular size of 0.02 arcseconds for the non-thermal component. This compact size favors the explanation in terms of a star with non-thermal emission or of a wind-collision region. Comment: Accepted for publication in RevMexAA
    05/2010;
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    ABSTRACT: We present high sensitivity H91alpha 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 a 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. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
    Revista mexicana de astronomía y astrofísica 01/2010; 46:29-35. · 1.20 Impact Factor
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    ABSTRACT: We present high sensitivity H91$\alpha$ and 3.5 cm radio continuum observations toward the planetary nebula NGC 3242. The electron temperature determined assuming local thermodynamic equilibrium is consistent within $\sim$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. Comment: 7 pages, 4 figures
    Revista mexicana de astronomía y astrofísica 11/2009; · 1.20 Impact Factor

Publication Stats

732 Citations
390.79 Total Impact Points

Institutions

  • 2003–2012
    • Universidad Nacional Autónoma de México
      • Centre of Radio Astronomy and Astrophysics
      Ciudad de México, The Federal District, Mexico
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States
  • 1991–2010
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
  • 1994–2003
    • University of Chile
      CiudadSantiago, Santiago, Chile
  • 2001
    • Institute of Geophysics and Astronomy
      La Habana, Ciudad de La Habana, Cuba
    • Spanish National Research Council
      • Andalusian Astrophysics Institute
      Madrid, Madrid, Spain