Distance to Orion KL Measured with VERA
25 Oct 2007-Publications of the Astronomical Society of Japan (Oxford University Press)-Vol. 59, Iss: 5, pp 897-903
TL;DR: In this article, the authors presented the initial results of multiepoch VLBI observations of 22 GHz H2O masers in the Orion KL region with VERA (VLBI Exploration of Radio Astrometry).
Abstract: We present the initial results of multiepoch VLBI observations of 22 GHz H2O masers in the Orion KL region with VERA (VLBI Exploration of Radio Astrometry). With the VERA dual-beam receiving system, we carried out phase-referencing VLBI astrometry, and successfully detected the annual parallax of Orion KL to be 2.29 ˙ 0.10 mas, corresponding to a distance of 437 ˙ 19 pc from the Sun. The distance to Orion KL was determined for the first time with the trigonometric parallax method in these observations. Although this value is consistent with that previously reported, 480 ˙ 80 pc, which was estimated from a statistical parallax method using the proper motions and radial velocities of the H2O maser features, our new results provide a much more accurate value with an uncertainty of only 4%. In addition to the annual parallax, we detected an absolute proper motion of the maser feature, suggesting an outflow motion powered by the radio source I along with the systematic motion of source I itself.
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TL;DR: In this paper, the authors review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies.
Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.
2,525 citations
Cites background from "Distance to Orion KL Measured with ..."
...The nearest young cluster that has formed O stars is 415-430 pc away in Orion (Menten et al. 2007; Hirota et al. 2007), and most lie at much larger distances, making study of the entire IMF difficult....
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TL;DR: In this article, the authors used the Very Long Baseline Array and the Japanese VLBI Exploration of Radio Astronomy project to measure trigonometric parallaxes and proper motions of masers found in high-mass star-forming regions across the Milky Way.
Abstract: We are using the Very Long Baseline Array and the Japanese VLBI Exploration of Radio Astronomy project to measure trigonometric parallaxes and proper motions of masers found in high-mass star-forming regions across the Milky Way. Early results from 18 sources locate several spiral arms. The Perseus spiral arm has a pitch angle of 16 degrees +/- 3 degrees, which favors four rather than two spiral arms for the Galaxy. Combining positions, distances, proper motions, and radial velocities yields complete three-dimensional kinematic information. We find that star-forming regions on average are orbiting the Galaxy approximate to 15 km s(-1) slower than expected for circular orbits. By fitting the measurements to a model of the Galaxy, we estimate the distance to the Galactic center R(0) = 8.4 +/- 0.6 kpc and a circular rotation speed Theta(0) = 254 +/- 16 km s(-1). The ratio Theta(0)/R(0) can be determined to higher accuracy than either parameter individually, and we find it to be 30.3 +/- 0.9 km s(-1) kpc(-1), in good agreement with the angular rotation rate determined from the proper motion of Sgr A*. The data favor a rotation curve for the Galaxy that is nearly flat or slightly rising with Galactocentric distance. Kinematic distances are generally too large, sometimes by factors greater than 2; they can be brought into better agreement with the trigonometric parallaxes by increasing Theta(0)/R(0) from the IAU recommended value of 25.9 km s(-1) kpc(-1) to a value near 30 km s(-1) kpc(-1). We offer a "revised" prescription for calculating kinematic distances and their uncertainties, as well as a new approach for defining Galactic coordinates. Finally, our estimates of Theta(0) and Theta(0)/R(0), when coupled with direct estimates of R(0), provide evidence that the rotation curve of the Milky Way is similar to that of the Andromeda galaxy, suggesting that the dark matter halos of these two dominant Local Group galaxy are comparably massive.
1,167 citations
Cites methods from "Distance to Orion KL Measured with ..."
...Eight other sources with H2O or SiO masers have been measured with VERA (Honma et al. 2007; Hirota et al. 2007; Choi et al. 2008; Sato et al. 2008) and with methanol, H2O or continuum emission with the VLBA (Hachisuka et al. 2006; Menten et al. 2007; Moellenbrock, Claussen & Goss 2007; Bartkiewicz…...
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TL;DR: In this paper, a survey of the Orion A and B molecular clouds undertaken with the IRAC and MIPS instruments on board Spitzer is presented, which includes the Orion Nebula Cluster, the Lynds 1641, 1630, and 1622 dark clouds, and the NGC 2023, 2024, 2068 and 2071 nebulae.
Abstract: We present a survey of the Orion A and B molecular clouds undertaken with the IRAC and MIPS instruments on board Spitzer. In total, five distinct fields were mapped, covering 9 deg^2 in five mid-IR bands spanning 3-24 μm. The survey includes the Orion Nebula Cluster, the Lynds 1641, 1630, and 1622 dark clouds, and the NGC 2023, 2024, 2068, and 2071 nebulae. These data are merged with the Two Micron All Sky Survey point source catalog to generate a catalog of eight-band photometry. We identify 3479 dusty young stellar objects (YSOs) in the Orion molecular clouds by searching for point sources with mid-IR colors indicative of reprocessed light from dusty disks or infalling envelopes. The YSOs are subsequently classified on the basis of their mid-IR colors and their spatial distributions are presented. We classify 2991 of the YSOs as pre-main-sequence stars with disks and 488 as likely protostars. Most of the sources were observed with IRAC in two to three epochs over six months; we search for variability between the epochs by looking for correlated variability in the 3.6 and 4.5 μm bands. We find that 50% of the dusty YSOs show variability. The variations are typically small (~0.2 mag) with the protostars showing a higher incidence of variability and larger variations. The observed correlations between the 3.6, 4.5, 5.8, and 8 μm variability suggests that we are observing variations in the heating of the inner disk due to changes in the accretion luminosity or rotating accretion hot spots.
466 citations
TL;DR: In this article, a survey of the Orion A and B molecular clouds undertaken with the IRAC and MIPS instruments onboard Spitzer is presented, which includes the Orion Nebula Cluster, the Lynds 1641, 1630 and 1622 dark clouds, and the NGC 2023, 2024, 2068 and 2071 nebulae.
Abstract: We present a survey of the Orion A and B molecular clouds undertaken with the IRAC and MIPS instruments onboard Spitzer. In total, five distinct fields were mapped covering 9 sq. degrees in five mid-IR bands spanning 3-24 microns. The survey includes the Orion Nebula Cluster, the Lynds 1641, 1630 and 1622 dark clouds, and the NGC 2023, 2024, 2068 and 2071 nebulae. These data are merged with the 2MASS point source catalog to generate a catalog of eight band photometry. We identify 3479 dusty young stellar objects (YSOs) in the Orion molecular clouds by searching for point sources with mid-IR colors indicative of reprocessed light from dusty disks or infalling envelopes. The YSOs are subsequently classified on the basis of their mid-IR colors and their spatial distributions are presented. We classify 2991 of the YSOs as pre-main sequence stars with disks and 488 as likely protostars. Most of the sources were observed with IRAC in 2-3 epochs over 6 months; we search for variability between the epochs by looking for correlated variability in the 3.6 and 4.5 micron bands. We find that 50% of the dusty YSOs show variability. The variations are typically small (0.2 mag.) with the protostars showing a higher incidence of variability and larger variations. The observed correlations between the 3.6, 4.5, 5.8 and 8 micron variability suggests that we are observing variations in the heating of the inner disk due to changes in the accretion luminosity or rotating accretion hot spots.
452 citations
Cites background from "Distance to Orion KL Measured with ..."
...VLBI parallax measurements of stars and masers in the Orion Nebula give an average distance of 420 pc (Sandstrom et al. 2007, Menten et al. 2007, Hirota et al. 2007)....
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TL;DR: In this article, the authors measured the annual parallax of the maser features in SVS 13 of 4.25 ˙ 0.32 mas, corresponding to a distance of 235 ˘ 18 pc from the Sun.
Abstract: We report on the results of multiepoch very long baseline interferometry (VLBI) observations with VERA (VLBI Exploration of Radio Astrometry) of the 22 GHz H2O masers associated with the young stellar object SVS 13 in the NGC 1333 region. We carried out phase-referencing VLBI astrometry, and measured the annual parallax of the maser features in SVS 13 of 4.25 ˙ 0.32 mas, corresponding to a distance of 235 ˙ 18 pc from the Sun. Our result is consistent with a photometric distance of 220 pc, previously reported. Even though the maser features were detectable only for 6 months, the present result provides the distance to NGC 1333 with much higher accuracy than photometric methods. The absolute positions and proper motions have been derived, revealing that the H2O masers with LSR (local standard of rest) velocities of 7–8 km s � 1 are most likely associated with VLA 4A, which is a radio counterpart of SVS 13. It is currently difficult to attribute the observed proper motions of the maser features to either the jet or the rotating circumstellar disk associated with VLA 4A, which should be investigated through future high-resolution astrometric observations of VLA 4A and other radio sources in NGC 1333.
332 citations
References
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TL;DR: A quasi-inertial reference frame is defined based on the radio positions of 212 extragalactic sources distributed over the entire sky as discussed by the authors, which is better than about 1 mas in both coordinates.
Abstract: A quasi-inertial reference frame is defined based on the radio positions of 212 extragalactic sources distributed over the entire sky. The positional accuracy of these sources is better than about 1 mas in both coordinates. The radio positions are based upon a general solution for all applicable dual-frequency 2.3 and 8.4 GHz Mark III very long baseline interferometry data available through the middle of 1995, consisting of 1.6 million pairs of group delay and phase delay rate observations. Positions and details are also given for an additional 396 objects that either need further observation or are currently unsuitable for the definition of a high-accuracy reference frame. The final orientation of the frame axes has been obtained by a rotation of the positions into the system of the International Celestial Reference System and is consistent with the FK5 J2000.0 optical system, within the limits of the link accuracy. The resulting International Celestial Reference Frame has been adopted by the International Astronomical Union as the fundamental celestial reference frame, replacing the FK5 optical frame as of 1998 January 1.
777 citations
"Distance to Orion KL Measured with ..." refers background or methods in this paper
...The uncertainty in the absolute position of the reference source J0541−0541, 0.28 mas and 0.46 mas in right ascension and declination, respectively (Ma et al. 1998), also does not affect the derived annual parallax and proper motion because this uncertainty gives only a constant offset to the…...
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...083385s, δ(J2000) = −05d41’49.42839”; Ma et al. 1998; Petrov et al. 2007) were observed simultaneously....
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...Using extragalactic radio sources as the position references (e.g. sources listed in the ICRF catalog; Ma et al. 1998), we can measure the absolute position of the target source, which lead us to derive its annual parallax....
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TL;DR: The distance to the massive star–forming region W3OH in the Perseus spiral arm of the Milky Way is measured by triangulation, with Earth's orbit as one segment of a triangle, using the Very Long Baseline Array, resolving the long-standing problem that there is a discrepancy between different techniques used to determine distances.
Abstract: We have measured the distance to the massive star-forming region W3OH in the Perseus spiral arm of the Milky Way to be 195 +/- 004 kiloparsecs (586 x10(16) km) This distance was determined by triangulation, with Earth's orbit as one segment of a triangle, using the Very Long Baseline Array This resolves the long-standing problem that there is a discrepancy of a factor of 2 between different techniques used to determine distances The reason for the discrepancy is that this portion of the Perseus arm has anomalous motions The orientation of the anomalous motion agrees with spiral density-wave theory, but the magnitude of the motion is somewhat larger than most models predict
429 citations
"Distance to Orion KL Measured with ..." refers methods in this paper
...With recent highly precise VLBI astrometry, annual parallaxes have been successfully measured for the Galactic CH3OH maser sources at the 12 GHz band (Xu et al. 2006) and H2O maser sources at the 22 GHz band (Kurayama et al. 2005; Hachisuka et al. 2006) with the NRAO Very Long Baseline Array (VLBA)....
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...…which provides a powerful tool to measure annual parallaxes with the accuracy by two orders of magnitude higher than that of the Hipparcos satellite, allowing us to measure the distances of maser sources up to 2 kpc away from the Sun (Kurayama et al. 2005; Xu et al. 2006; Hachisuka et al. 2006)....
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TL;DR: The structure du nuage moleculaire geant Orion, sa compostion stellaire, l'interaction entre les etoiles OB de Orion A et le nuage, and la region de formation stellaires BN-IRc 2 sont etudiees.
Abstract: La structure du nuage moleculaire geant Orion, sa compostion stellaire, l'interaction entre les etoiles OB de Orion A et le nuage, et la region de formation stellaire BN-IRc 2 sont etudiees. De nombreuses references bibliographiques sont citees
412 citations
"Distance to Orion KL Measured with ..." refers background in this paper
...Because Orion KL is the nearest high-mass star-forming region located at an estimated distance of only 480 pc from the Sun (Genzel et al. 1981), it has been recognized as one of the most important objects to study high-mass star-formation processes (e.g. Genzel & Stutzki 1989)....
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TL;DR: In this article, a detailed analysis of the chopper-wheel method of calibrating the intensity of a millimeter-wavelength spectral line is presented, and the effects of the antenna power pattern on the corrected antenna temperature T*/sub A/ are calculated for several simple models of the source brightness distribution.
Abstract: A detailed analysis of the chopper-wheel method of calibrating the intensity of a millimeter-wavelength spectral line is presented. Special techniques were used to construct a receiver which eliminates most of the usual calibration difficulties. The zenith atmospheric extinction between 3.5 mm and 2.6 mm wavelength was measured, and the intensities of six spectral lines in this range were absolutely calibrated with an estimated uncertainty (1 sigma) of 7 percent. The effects of the antenna power pattern on the corrected antenna temperature T*/sub A/ are calculated for several simple models of the source brightness distribution. (auth)
331 citations
"Distance to Orion KL Measured with ..." refers methods in this paper
...System temperatures including atmospheric attenuation were measured with the chopper-wheel method (Ulich & Haas 1976) to be 100-600 K, depending on weather conditions and elevation angle of the observed sources....
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01 Dec 1988
TL;DR: The structure du nuage moleculaire geant Orion, sa compostion stellaire, l'interaction entre les etoiles OB de Orion A et le nuage, and la region de formation stellaires BN-IRc 2 sont etudiees as mentioned in this paper.
Abstract: La structure du nuage moleculaire geant Orion, sa compostion stellaire, l'interaction entre les etoiles OB de Orion A et le nuage, et la region de formation stellaire BN-IRc 2 sont etudiees. De nombreuses references bibliographiques sont citees
314 citations