# Publication Search Results

## Search Results

Showing 1-20 of about 36 results.
Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner GalaxyXu, Y.Bian, S. B.Reid, M. J.Li, J. J.Menten, K. M.Dame, T. M.Zhang, B.Brunthaler, A.Wu, Y. W.Moscadelli, L.Wu, G.Zheng, X. W.DOI: info:10.3847/1538-4365/abd8cfv. 2531
Xu, Y., Bian, S. B., Reid, M. J., Li, J. J., Menten, K. M., Dame, T. M., Zhang, B., Brunthaler, A., Wu, Y. W., Moscadelli, L., Wu, G., and Zheng, X. W. 2021. "Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner Galaxy." The Astrophysical Journal Supplement Series 253:1. https://doi.org/10.3847/1538-4365/abd8cf
ID: 159444
Type: article
Authors: Xu, Y.; Bian, S. B.; Reid, M. J.; Li, J. J.; Menten, K. M.; Dame, T. M.; Zhang, B.; Brunthaler, A.; Wu, Y. W.; Moscadelli, L.; Wu, G.; Zheng, X. W.
Abstract: We have measured trigonometric parallaxes for four H2O masers associated with distant massive young stars in the inner regions of the Galaxy using the Very Long Baseline Array as part of the BeSSeL Survey. G026.50 + 0.28 is located at the near end of the Galactic bar, perhaps at the origin of the Norma spiral arm. G020.77−0.05 is in the Galactic Center region and is likely associated with a far-side extension of the Scutum arm. G019.60−0.23 and G020.08−0.13 are likely associated and lie well past the Galactic Center. These sources appear to be in the Sagittarius spiral arm, but an association with the Perseus arm cannot be ruled out.
The Mass-Size Relation and the Constancy of GMC Surface Densities in the Milky WayLada, Charles J.Dame, Thomas M.DOI: info:10.3847/1538-4357/ab9bfbv. 8983
Lada, Charles J. and Dame, Thomas M. 2020. "The Mass-Size Relation and the Constancy of GMC Surface Densities in the Milky Way." The Astrophysical Journal 898:3. https://doi.org/10.3847/1538-4357/ab9bfb
ID: 157656
Type: article
Authors: Lada, Charles J.; Dame, Thomas M.
Abstract: We use two existing molecular cloud catalogs derived from the same CO survey and two catalogs derived from local dust extinction surveys to investigate the nature of the giant molecular cloud (GMC) mass-size relation in the Galaxy. We find that the four surveys are well described by MGMC ∼ R2, implying a constant mean surface density, ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ , for the cataloged clouds. However, the scaling coefficients and scatter differ significantly between the CO- and extinction-derived relations. We find that the additional scatter seen in the CO relations is due to a systematic variation in ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ with Galactic radius that is unobservable in the local extinction data. We decompose this radial variation of ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ into two components, a linear negative gradient with Galactic radius and a broad peak coincident with the molecular ring and superposed on the linear gradient. We show that the former may be due to a radial dependence of XCO on metallicity, while the latter likely results from a combination of increased surface densities of individual GMCs and a systematic upward bias in the measurements of ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ due to cloud blending in the molecular ring. We attribute the difference in scaling coefficients between the CO and extinction data to an underestimate of XCO. We recalibrate the CO observations of nearby GMCs using extinction measurements to find that locally XCO = 3.6 ± 0.3 × 1020 cm-2 (K km s-1)-1. We conclude that outside the molecular ring, the GMC population of the Galaxy can be described to relatively good precision by a constant ${{\rm{\Sigma }}}_{\mathrm{GMC}}$ of 35 ${M}_{\odot }$ pc-2.
Trigonometric Parallaxes of High-mass Star-forming Regions: Our View of the Milky WayReid, Mark J.Menten, K. M.Brunthaler, A.Zheng, X. W.Dame, Thomas M.Xu, Y.Li, J.Sakai, N.Wu, Y.Immer, K.Zhang, B.Sanna, A.Moscadelli, L.Rygl, K. L. J.Bartkiewicz, A.Hu, B.Quiroga-Nuñez, L. H.van Langevelde, H. J.DOI: info:10.3847/1538-4357/ab4a11v. 885131
Reid, Mark J., Menten, K. M., Brunthaler, A., Zheng, X. W., Dame, Thomas M., Xu, Y., Li, J., Sakai, N., Wu, Y., Immer, K., Zhang, B., Sanna, A., Moscadelli, L., Rygl, K. L. J., Bartkiewicz, A., Hu, B., Quiroga-Nuñez, L. H., and van Langevelde, H. J. 2019. "Trigonometric Parallaxes of High-mass Star-forming Regions: Our View of the Milky Way." The Astrophysical Journal 885:131. https://doi.org/10.3847/1538-4357/ab4a11
ID: 154604
Type: article
Authors: Reid, Mark J.; Menten, K. M.; Brunthaler, A.; Zheng, X. W.; Dame, Thomas M.; Xu, Y.; Li, J.; Sakai, N.; Wu, Y.; Immer, K.; Zhang, B.; Sanna, A.; Moscadelli, L.; Rygl, K. L. J.; Bartkiewicz, A.; Hu, B.; Quiroga-Nuñez, L. H.; van Langevelde, H. J.
Abstract: We compile and analyze approximately 200 trigonometric parallaxes and proper motions of molecular masers associated with very young high-mass stars. Most of the measurements come from the BeSSeL Survey using the VLBA and the Japanese VERA project. These measurements strongly suggest that the Milky Way is a four-arm spiral, with some extra arm segments and spurs. Fitting log-periodic spirals to the locations of the masers, allowing for "kinks" in the spirals and using well-established arm tangencies in the fourth Galactic quadrant, allows us to significantly expand our view of the structure of the Milky Way. We present an updated model for its spiral structure and incorporate it into our previously published parallax-based distance-estimation program for sources associated with spiral arms. Modeling the three-dimensional space motions yields estimates of the distance to the Galactic center, {R}0=8.15+/- 0.15 {kpc}, the circular rotation speed at the Sun's position, {{{\Theta }}}0=236+/- 7 km s-1, and the nature of the rotation curve. Our data strongly constrain the full circular velocity of the Sun, {{{\Theta }}}0+{V}=247+/- 4 km s-1, and its angular velocity, ({{{\Theta }}}0+{V})/{R}0=30.32+/- 0.27 km s-1 kpc-1. Transforming the measured space motions to a Galactocentric frame which rotates with the Galaxy, we find non- circular velocity components typically ≲10 km s-1. However, near the Galactic bar and in a portion of the Perseus arm we find significantly larger non-circular motions. Young high-mass stars within 7 kpc of the Galactic center have a scale height of only 19 pc, and thus are well suited to define the Galactic plane. We find that the orientation of the plane is consistent with the IAU-defined plane to within ±0.°1, and that the Sun is offset toward the north Galactic pole by {Z}=5.5+/- 5.8 pc. Accounting for this offset places the central supermassive black hole, Sgr A*, in the midplane of the Galaxy. The measured motions perpendicular to the plane of the Galaxy limit precession of the plane to ≲4 km s-1 at the radius of the Sun. Using our improved Galactic parameters, we predict the Hulse-Taylor binary pulsar to be at a distance of 6.54 ± 0.24 kpc, assuming its orbital decay from gravitational radiation follows general relativity.
Noncircular Motions in the Outer Perseus Spiral ArmSakai, NobuyukiReid, Mark J.Menten, Karl M.Brunthaler, AndreasDame, Thomas M.DOI: info:10.3847/1538-4357/ab12e0v. 87630
Sakai, Nobuyuki, Reid, Mark J., Menten, Karl M., Brunthaler, Andreas, and Dame, Thomas M. 2019. "Noncircular Motions in the Outer Perseus Spiral Arm." The Astrophysical Journal 876:30. https://doi.org/10.3847/1538-4357/ab12e0
ID: 151847
Type: article
Authors: Sakai, Nobuyuki; Reid, Mark J.; Menten, Karl M.; Brunthaler, Andreas; Dame, Thomas M.
Abstract: We report measurements of parallax and proper motion for five 6.7 GHz methanol maser sources in the outer regions of the Perseus arm as part of the BeSSeL Survey of the Galaxy. By combining our results with previous astrometric results, we determine an average spiral arm pitch angle of 9.°2 ± 1.°5 and an arm width of 0.39 kpc for this spiral arm. For sources on the interior side of the Perseus arm, we find on average a radial inward motion in the Galaxy of 13.3 ± 5.4 km s‑1 and counter to Galactic rotation of 6.2 ± 3.2 km s‑1. These characteristics are consistent with models for spiral arm formation that involve gas entering an arm to be shocked and then to form stars. However, similar data for other spiral arms do not show similar characteristics.
Trigonometric Parallaxes of Star-forming Regions beyond the Tangent Point of the Sagittarius Spiral ArmWu, Y. W.Reid, Mark J.Sakai, N.Dame, Thomas M.Menten, K. M.Brunthaler, A.Xu, Y.Li, J. J.Ho, B.Zhang, B.Rygl, K. L. J.Zheng, X. W.DOI: info:10.3847/1538-4357/ab001av. 87494
Wu, Y. W., Reid, Mark J., Sakai, N., Dame, Thomas M., Menten, K. M., Brunthaler, A., Xu, Y., Li, J. J., Ho, B., Zhang, B., Rygl, K. L. J., and Zheng, X. W. 2019. "Trigonometric Parallaxes of Star-forming Regions beyond the Tangent Point of the Sagittarius Spiral Arm." The Astrophysical Journal 874:94. https://doi.org/10.3847/1538-4357/ab001a
ID: 155412
Type: article
Authors: Wu, Y. W.; Reid, Mark J.; Sakai, N.; Dame, Thomas M.; Menten, K. M.; Brunthaler, A.; Xu, Y.; Li, J. J.; Ho, B.; Zhang, B.; Rygl, K. L. J.; Zheng, X. W.
Abstract: As part of the BeSSeL Survey, we report trigonometric parallaxes and proper motions of molecular maser sources associated with 13 distant high-mass star-forming regions in the Sagittarius spiral arm of the Milky Way. In particular, we obtain improved parallax distance estimates for three well-studied regions: {1.9}-0.1+0.1 {kpc} for M17, {5.3}-0.9+1.3 {kpc} for W51, and {7.9}-0.7+0.9 {kpc} for GAL 045.5+00.0. Peculiar motions for all but one source are less than 20 km s-1. We fit a log-periodic spiral to the locations and estimate an average pitch angle of 7.°2 ± 1.°9. We find that the section of the arm beyond the tangent point in the first quadrant of the Milky Way appears 15 pc below the IAU-defined Galactic plane.
Parallaxes for Star-forming Regions in the Inner Perseus Spiral ArmZhang, BoReid, Mark J.Zhang, LianWu, YuanweiHu, BoSakai, NobuyukiMenten, Karl M.Zheng, XingwuBrunthaler, AndreasDame, Thomas M.Xu, YeDOI: info:10.3847/1538-3881/ab141dv. 157200
Zhang, Bo, Reid, Mark J., Zhang, Lian, Wu, Yuanwei, Hu, Bo, Sakai, Nobuyuki, Menten, Karl M., Zheng, Xingwu, Brunthaler, Andreas, Dame, Thomas M., and Xu, Ye. 2019. "Parallaxes for Star-forming Regions in the Inner Perseus Spiral Arm." The Astronomical Journal 157:200. https://doi.org/10.3847/1538-3881/ab141d
ID: 151849
Type: article
Authors: Zhang, Bo; Reid, Mark J.; Zhang, Lian; Wu, Yuanwei; Hu, Bo; Sakai, Nobuyuki; Menten, Karl M.; Zheng, Xingwu; Brunthaler, Andreas; Dame, Thomas M.; Xu, Ye
Abstract: We report trigonometric parallax and proper motion measurements of 6.7 GHz CH3OH and 22 GHz H2O masers in eight high-mass star-forming regions (HMSFRs) based on Very Long Baseline Array (VLBA) observations as part of the Bar and Spiral Structure Legacy (BeSSeL) Survey. The distances of these HMSFRs combined with their Galactic coordinates, radial velocities, and proper motions, allow us to assign them to a segment of the Perseus arm with ℓ ≲ 70°. These HMSFRs are clustered in Galactic longitude from ≈30° to ≈50° neighboring a dearth of such sources between longitudes ≈50° to ≈90°.
High-mass Star Formation in the Outer Scutum-Centaurus ArmArmentrout, W. P.Anderson, L. D.Balser, Dana S.Bania, T. M.Dame, T. M.Wenger, Trey V.DOI: info:10.3847/1538-4357/aa71a1v. 841121
Armentrout, W. P., Anderson, L. D., Balser, Dana S., Bania, T. M., Dame, T. M., and Wenger, Trey V. 2017. "High-mass Star Formation in the Outer Scutum-Centaurus Arm." The Astrophysical Journal 841:121. https://doi.org/10.3847/1538-4357/aa71a1
ID: 143370
Type: article
Authors: Armentrout, W. P.; Anderson, L. D.; Balser, Dana S.; Bania, T. M.; Dame, T. M.; Wenger, Trey V.
Abstract: The Outer Scutum-Centaurus (OSC) spiral arm is the most distant molecular spiral arm in the Milky Way, but until recently little was known about this structure. Discovered by Dame and Thaddeus, the OSC lies ~15 kpc from the Galactic Center. Due to the Galactic warp, it rises to nearly 4° above the Galactic Plane in the first Galactic quadrant, leaving it unsampled by most Galactic plane surveys. Here we observe H ii region candidates spatially coincident with the OSC using the Very Large Array to image radio continuum emission from 65 targets and the Green Bank Telescope to search for ammonia and water maser emission from 75 targets. This sample, drawn from the Wide-field Infrared Survey Explorer Catalog of Galactic H ii Regions, represents every H ii region candidate near the longitude-latitude ({\ell },b) locus of the OSC. Coupled with their characteristic mid-infrared morphologies, detection of radio continuum emission strongly suggests that a target is a bona fide H ii region. Detections of associated ammonia or water maser emission allow us to derive a kinematic distance and determine if the velocity of the region is consistent with that of the OSC. Nearly 60% of the observed sources were detected in radio continuum, and more than 20% have ammonia or water maser detections. The velocities of these sources mainly place them beyond the Solar orbit. These very distant high-mass stars have stellar spectral types as early as O4. We associate high-mass star formation at 2 new locations with the OSC, increasing the total number of detected H ii regions in the OSC to 12.
Dame, Thomas. 2017. "Patrick Thaddeus." Nature Astronomy 1:0170. https://doi.org/10.1038/s41550-017-0170
ID: 143786
Type: article
Authors: Dame, Thomas
Abstract: A pioneer in the field of astrochemistry, Patrick Thaddeus discovered dozens of exotic molecules in space and helped revolutionize our view of the interstellar medium and star formation.
Mapping spiral structure on the far side of the Milky WaySanna, AlbertoReid, Mark J.Dame, Thomas M.Menten, Karl M.Brunthaler, AndreasDOI: info:10.1126/science.aan5452v. 358227â€“230
Sanna, Alberto, Reid, Mark J., Dame, Thomas M., Menten, Karl M., and Brunthaler, Andreas. 2017. "Mapping spiral structure on the far side of the Milky Way." Science 358:227– 230. https://doi.org/10.1126/science.aan5452
ID: 144738
Type: article
Authors: Sanna, Alberto; Reid, Mark J.; Dame, Thomas M.; Menten, Karl M.; Brunthaler, Andreas
Abstract: Little is known about the portion of the Milky Way lying beyond the Galactic center at distances of more than 9 kiloparsec from the Sun. These regions are opaque at optical wavelengths because of absorption by interstellar dust, and distances are very large and hard to measure. We report a direct trigonometric parallax distance of 20.4-2.2+2.8 kiloparsec obtained with the Very Long Baseline Array to a water maser source in a region of active star formation. These measurements allow us to shed light on Galactic spiral structure by locating the Scutum-Centaurus spiral arm as it passes through the far side of the Milky Way and to validate a kinematic method for determining distances in this region on the basis of transverse motions.
On the distance to the North Polar Spur and the local CO-H2 factorLallement, R.Snowden, S.Kuntz, K. D.Dame, T. M.Koutroumpa, D.Grenier, I.Casandjian, J. M.DOI: info:10.1051/0004-6361/201629453v. 595A131
Lallement, R., Snowden, S., Kuntz, K. D., Dame, T. M., Koutroumpa, D., Grenier, I., and Casandjian, J. M. 2016. "On the distance to the North Polar Spur and the local CO-H2 factor." Astronomy and Astrophysics 595:A131. https://doi.org/10.1051/0004-6361/201629453
ID: 141927
Type: article
Authors: Lallement, R.; Snowden, S.; Kuntz, K. D.; Dame, T. M.; Koutroumpa, D.; Grenier, I.; Casandjian, J. M.
Abstract:
Aims: Most models identify the X-ray bright North Polar Spur (NPS) with a hot interstellar (IS) bubble in the Sco-Cen star-forming region at ?130 pc. An opposite view considers the NPS as a distant structure associated with Galactic nuclear outflows. Constraints on the NPS distance can be obtained by comparing the foreground IS gas column inferred from X-ray absorption to the distribution of gas and dust along the line of sight. Absorbing columns toward shadowing molecular clouds simultaneously constrain the CO-H2 conversion factor.
Methods: We derived the columns of X-ray absorbing matter NHabs from spectral fitting of dedicated XMM-Newton observations toward the NPS southern terminus (lII ? 29°, bII ? + 5 to + 11°). The distribution of the IS matter was obtained from absorption lines in new stellar spectra, 3D dust maps, and emission data, including high spatial resolution CO measurements recorded for this purpose.
Results: NHabs varies from ?4.3 to ?1.3 × 1021 cm-2 along the 19 fields. Relationships between X-ray brightness, absorbing column, and hardness ratio demonstrate a brightness increase with latitude that is governed by increasing absorption. The comparison with absorption data and local and large-scale dust maps rules out an NPS source near-side closer than 300 pc. The correlation between NHabs and the reddening increases with the sightline length from 300 pc to 4 kpc and is the tightest with Planck t353 GHz-based reddening, suggesting a much larger distance. N(H)/E(B-V)t ? 4.1 × 1021 cm-2 mag-1, close to Fermi-Planck determinations. NHabs absolute values are compatible with HI-CO clouds at -5 = VLSR = + 25 to +45 km s-1 and an NPS potentially far beyond the Local Arm. A shadow cast by a b = + 9° molecular cloud constrains XCO in that direction to =1.0 × 1020 cm-2 K-1 km-1 s. The average XCO over the fields is =0.75 × 1020 cm-2 K-1 km-1 s. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Based on data obtained using the télescope Bernard Lyot at Observatoire du Pic du Midi, CNRS and Université Paul Sabatier, France.
On the Rotation Speed of the Milky Way Determined from H i EmissionReid, M. J.Dame, T. M.DOI: info:10.3847/0004-637X/832/2/159v. 832159
Reid, M. J. and Dame, T. M. 2016. "On the Rotation Speed of the Milky Way Determined from H i Emission." The Astrophysical Journal 832:159. https://doi.org/10.3847/0004-637X/832/2/159
ID: 141967
Type: article
Authors: Reid, M. J.; Dame, T. M.
Abstract: The circular rotation speed of the Milky Way at the solar radius, T0, has been estimated to be 220 km s-1 by fitting the maximum velocity of H i emission as a function of Galactic longitude. This result is in tension with a recent estimate of T0 = 240 km s-1, based on Very Long Baseline Interferometry (VLBI) parallaxes and proper motions from the BeSSeL and VERA surveys for large numbers of high-mass star-forming regions across the Milky Way. We find that the rotation curve best fitted to the VLBI data is slightly curved, and that this curvature results in a biased estimate of T0 from the H i data when a flat rotation curve is assumed. This relieves the tension between the methods and favors T0 = 240 km s-1.
A Uniform Catalog of Molecular Clouds in the Milky WayRice, Thomas S.Goodman, Alyssa A.Bergin, Edwin A.Beaumont, ChristopherDame, T. M.DOI: info:10.3847/0004-637X/822/1/52v. 82252
Rice, Thomas S., Goodman, Alyssa A., Bergin, Edwin A., Beaumont, Christopher, and Dame, T. M. 2016. "A Uniform Catalog of Molecular Clouds in the Milky Way." The Astrophysical Journal 822:52. https://doi.org/10.3847/0004-637X/822/1/52
ID: 139807
Type: article
Authors: Rice, Thomas S.; Goodman, Alyssa A.; Bergin, Edwin A.; Beaumont, Christopher; Dame, T. M.
Abstract: The all-Galaxy CO survey of Dame et al. is by far the most uniform, large-scale Galactic CO survey. Using a dendrogram-based decomposition of this survey, we present a catalog of 1064 massive molecular clouds throughout the Galactic plane. This catalog contains 2.5 × 108 solar masses, or {25}-5.8+10.7% of the Milky Way's estimated H2 mass. We track clouds in some spiral arms through multiple quadrants. The power index of Larson's first law, the size-linewidth relation, is consistent with 0.5 in all regions—possibly due to an observational bias—but clouds in the inner Galaxy systematically have significantly (~30%) higher linewidths at a given size, indicating that their linewidths are set in part by the Galactic environment. The mass functions of clouds in the inner Galaxy versus the outer Galaxy are both qualitatively and quantitatively distinct. The inner Galaxy mass spectrum is best described by a truncated power law with a power index of ? = -1.6 ± 0.1 and an upper truncation mass of M 0 = (1.0 ± 0.2) × 107 M ?, while the outer Galaxy mass spectrum is better described by a non-truncating power law with ? = -2.2 ± 0.1 and an upper mass of M 0 = (1.5 ± 0.5) × 106 M ?, indicating that the inner Galaxy is able to form and host substantially more massive GMCs than the outer Galaxy. Additionally, we have simulated how the Milky Way would appear in CO from extragalactic perspectives, for comparison with CO maps of other galaxies.
Parallaxes of Star-forming Regions in the Outer Spiral Arm of the Milky WayHachisuka, K.Choi, Y. K.Reid, M. J.Brunthaler, A.Menten, K. M.Sanna, A.Dame, T. M.DOI: info:10.1088/0004-637X/800/1/2v. 8002
Hachisuka, K., Choi, Y. K., Reid, M. J., Brunthaler, A., Menten, K. M., Sanna, A., and Dame, T. M. 2015. "Parallaxes of Star-forming Regions in the Outer Spiral Arm of the Milky Way." The Astrophysical Journal 800:2. https://doi.org/10.1088/0004-637X/800/1/2
ID: 135192
Type: article
Authors: Hachisuka, K.; Choi, Y. K.; Reid, M. J.; Brunthaler, A.; Menten, K. M.; Sanna, A.; Dame, T. M.
Abstract: We report parallaxes and proper motions of three water maser sources in high-mass star-forming regions in the Outer Spiral Arm of the Milky Way. The observations were conducted with the Very Long Baseline Array as part of Bar and Spiral Structure Legacy Survey and double the number of such measurements in the literature. The Outer Arm has a pitch angle of 14.°9 ± 2.°7 and a Galactocentric distance of 14.1 ± 0.6 kpc toward the Galactic anticenter. The average motion of these sources toward the Galactic center is 10.7 ± 2.1 km s–1 and we see no sign of a significant fall in the rotation curve out to 15 kpc from the Galactic center. The three-dimensional locations of these star-forming regions are consistent with a Galactic warp of several hundred parsecs from the plane.
Trigonometric Parallaxes of Star Forming Regions in the Perseus Spiral ArmChoi, Y. K.Hachisuka, K.Reid, M. J.Xu, Y.Brunthaler, A.Menten, K. M.Dame, T. M.DOI: info:10.1088/0004-637X/790/2/99v. 79099
Choi, Y. K., Hachisuka, K., Reid, M. J., Xu, Y., Brunthaler, A., Menten, K. M., and Dame, T. M. 2014. "Trigonometric Parallaxes of Star Forming Regions in the Perseus Spiral Arm." The Astrophysical Journal 790:99. https://doi.org/10.1088/0004-637X/790/2/99
ID: 128156
Type: article
Authors: Choi, Y. K.; Hachisuka, K.; Reid, M. J.; Xu, Y.; Brunthaler, A.; Menten, K. M.; Dame, T. M.
Abstract: We report trigonometric parallaxes and proper motions of water masers for 12 massive star forming regions in the Perseus spiral arm of the Milky Way as part of the Bar and Spiral Structure Legacy (BeSSel) Survey. Combining our results with 14 parallax measurements in the literature, we estimate a pitch angle of 9.°9 ± 1.°5 for a section of the Perseus arm. The three-dimensional Galactic peculiar motions of these sources indicate that on average they are moving toward the Galactic center and slower than the Galactic rotation.
The Jet and Arc Molecular Clouds toward Westerlund 2, RCW 49, and HESS J1023–575 12CO and 13CO (J = 2-1 and J = 1-0) observations with NANTEN2 and Mopra TelescopeFurukawa, N.Ohama, A.Fukuda, T.Torii, K.Hayakawa, T.Sano, H.Okuda, T.Yamamoto, H.Moribe, N.Mizuno, A.Maezawa, H.Onishi, T.Kawamura, A.Mizuno, N.Dawson, J. R.Dame, T. M.Yonekura, Y.Aharonian, F.de Oña Wilhelmi, E.Rowell, G. P.Matsumoto, R.Asahina, Y.Fukui, Y.DOI: info:10.1088/0004-637X/781/2/70v. 78170
Furukawa, N., Ohama, A., Fukuda, T., Torii, K., Hayakawa, T., Sano, H., Okuda, T., Yamamoto, H., Moribe, N., Mizuno, A., Maezawa, H., Onishi, T., Kawamura, A., Mizuno, N., Dawson, J. R., Dame, T. M., Yonekura, Y., Aharonian, F., de Oña Wilhelmi, E., Rowell, G. P., Matsumoto, R., Asahina, Y., and Fukui, Y. 2014. "The Jet and Arc Molecular Clouds toward Westerlund 2, RCW 49, and HESS J1023–575 12CO and 13CO (J = 2-1 and J = 1-0) observations with NANTEN2 and Mopra Telescope." The Astrophysical Journal 781:70. https://doi.org/10.1088/0004-637X/781/2/70
ID: 119088
Type: article
Authors: Furukawa, N.; Ohama, A.; Fukuda, T.; Torii, K.; Hayakawa, T.; Sano, H.; Okuda, T.; Yamamoto, H.; Moribe, N.; Mizuno, A.; Maezawa, H.; Onishi, T.; Kawamura, A.; Mizuno, N.; Dawson, J. R.; Dame, T. M.; Yonekura, Y.; Aharonian, F.; de Oña Wilhelmi, E.; Rowell, G. P.; Matsumoto, R.; Asahina, Y.; Fukui, Y.
Abstract: We have made new CO observations of two molecular clouds, which we call "jet" and "arc" clouds, toward the stellar cluster Westerlund 2 and the TeV γ-ray source HESS J1023–575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023–575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be ~Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV γ-ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV γ-rays, although none of the known microquasars have a Myr age or steady TeV γ-rays. Alternatively, an anisotropic supernova explosion which occurred ~Myr ago may be able to form the jet and arc clouds, whereas the TeV γ-ray emission requires a microquasar formed after the explosion.
Giant Molecular Clouds and Massive Star Formation in the Southern Milky WayGarcía, P.Bronfman, L.Nyman, Lars-ÅkeDame, T. M.Luna, A.DOI: info:10.1088/0067-0049/212/1/2v. 2122
García, P., Bronfman, L., Nyman, Lars-Åke, Dame, T. M., and Luna, A. 2014. "Giant Molecular Clouds and Massive Star Formation in the Southern Milky Way." The Astrophysical Journal Supplement Series 212:2. https://doi.org/10.1088/0067-0049/212/1/2
ID: 123006
Type: article
Authors: García, P.; Bronfman, L.; Nyman, Lars-Åke; Dame, T. M.; Luna, A.
Abstract: The Columbia University-Universidad de Chile CO Survey of the southern Milky Way is used to separate the CO(1-0) emission of the fourth Galactic quadrant within the solar circle into its dominant components, giant molecular clouds (GMCs). After the subtraction of an axisymmetric model of the CO background emission in the inner southern Galaxy, 92 GMCs are identified, and for 87 of them the twofold distance ambiguity is solved. Their total molecular mass is M(H2) = 1.14 ± 0.05 × 108 M ?, accounting for around 40% of the molecular mass estimated from an axisymmetric analysis of the H2 volume density in the Galactic disk, M(H2)disk = 3.03 × 108 M ?. The large-scale spiral structure in the southern Galaxy, within the solar circle, is traced by the GMCs in our catalog; three spiral arm segments, the Centaurus, Norma, and 3 kpc expanding arm, are analyzed. After fitting a logarithmic spiral arm model to the arms, tangent directions at 310°, 330°, and 338°, respectively, are found, consistent with previous values from the literature. A complete CS(2-1) survey toward IRAS point-like sources with far-IR colors characteristic of ultracompact H II regions is used to estimate the massive star formation rate per unit H2 mass (MSFR) and the massive star formation efficiency (epsilon) for GMCs. The average MSFR for GMCs is 0.41 ± 0.06 L ?/M ?, and for the most massive clouds in the Norma arm it is 0.58 ± 0.09 L ?/M ?. Massive star formation efficiencies of GMCs are, on average, 3% of their available molecular mass.
The Bones of the Milky WayGoodman, Alyssa A.Alves, JoãoBeaumont, Christopher N.Benjamin, Robert A.Borkin, Michelle A.Burkert, AndreasDame, Thomas M.Jackson, JamesKauffmann, JensRobitaille, ThomasSmith, Rowan J.DOI: info:10.1088/0004-637X/797/1/53v. 79753
Goodman, Alyssa A., Alves, João, Beaumont, Christopher N., Benjamin, Robert A., Borkin, Michelle A., Burkert, Andreas, Dame, Thomas M., Jackson, James, Kauffmann, Jens, Robitaille, Thomas, and Smith, Rowan J. 2014. "The Bones of the Milky Way." The Astrophysical Journal 797:53. https://doi.org/10.1088/0004-637X/797/1/53
ID: 133429
Type: article
Authors: Goodman, Alyssa A.; Alves, João; Beaumont, Christopher N.; Benjamin, Robert A.; Borkin, Michelle A.; Burkert, Andreas; Dame, Thomas M.; Jackson, James; Kauffmann, Jens; Robitaille, Thomas; Smith, Rowan J.
Abstract: The very long and thin infrared dark cloud "Nessie" is even longer than had been previously claimed, and an analysis of its Galactic location suggests that it lies directly in the Milky Way's mid-plane, tracing out a highly elongated bone-like feature within the prominent Scutum-Centaurus spiral arm. Re-analysis of mid-infrared imagery from the Spitzer Space Telescope shows that this infrared dark cloud (IRDC) is at least two and possibly as many as five times longer than had originally been claimed by Nessie's discoverers; its aspect ratio is therefore at least 300:1 and possibly as large as 800:1. A careful accounting for both the Sun's offset from the Galactic plane (~25 pc) and the Galactic center's offset from the (lII , bII ) = (0, 0) position shows that the latitude of the true Galactic mid-plane at the 3.1 kpc distance to the Scutum-Centaurus Arm is not b = 0, but instead closer to b = –0.4, which is the latitude of Nessie to within a few parsecs. An analysis of the radial velocities of low-density (CO) and high-density (NH3) gas associated with the Nessie dust feature suggests that Nessie runs along the Scutum-Centaurus Arm in position-position-velocity space, which means it likely forms a dense "spine" of the arm in real space as well. The Scutum-Centaurus Arm is the closest major spiral arm to the Sun toward the inner Galaxy, and, at the longitude of Nessie, it is almost perpendicular to our line of sight, making Nessie the easiest feature to see as a shadow elongated along the Galactic plane from our location. Future high-resolution dust mapping and molecular line observations of the harder-to-find Galactic "bones" should allow us to exploit the Sun's position above the plane to gain a (very foreshortened) view "from above" the Milky Way's structure.
Trigonometric Parallaxes of High Mass Star Forming Regions: The Structure and Kinematics of the Milky WayReid, M. J.Menten, K. M.Brunthaler, A.Zheng, X. W.Dame, T. M.Xu, Y.Wu, Y.Zhang, B.Sanna, A.Sato, M.Hachisuka, K.Choi, Y. K.Immer, K.Moscadelli, L.Rygl, K. L. J.Bartkiewicz, A.DOI: info:10.1088/0004-637X/783/2/130v. 783130
Reid, M. J., Menten, K. M., Brunthaler, A., Zheng, X. W., Dame, T. M., Xu, Y., Wu, Y., Zhang, B., Sanna, A., Sato, M., Hachisuka, K., Choi, Y. K., Immer, K., Moscadelli, L., Rygl, K. L. J., and Bartkiewicz, A. 2014. "Trigonometric Parallaxes of High Mass Star Forming Regions: The Structure and Kinematics of the Milky Way." The Astrophysical Journal 783:130. https://doi.org/10.1088/0004-637X/783/2/130
ID: 120714
Type: article
Authors: Reid, M. J.; Menten, K. M.; Brunthaler, A.; Zheng, X. W.; Dame, T. M.; Xu, Y.; Wu, Y.; Zhang, B.; Sanna, A.; Sato, M.; Hachisuka, K.; Choi, Y. K.; Immer, K.; Moscadelli, L.; Rygl, K. L. J.; Bartkiewicz, A.
Trigonometric Parallaxes to Star-forming Regions within 4 kpc of the Galactic CenterSanna, A.Reid, M. J.Menten, K. M.Dame, T. M.Zhang, B.Sato, M.Brunthaler, A.Moscadelli, L.Immer, K.DOI: info:10.1088/0004-637X/781/2/108v. 781108
Sanna, A., Reid, M. J., Menten, K. M., Dame, T. M., Zhang, B., Sato, M., Brunthaler, A., Moscadelli, L., and Immer, K. 2014. "Trigonometric Parallaxes to Star-forming Regions within 4 kpc of the Galactic Center." The Astrophysical Journal 781:108. https://doi.org/10.1088/0004-637X/781/2/108
ID: 119061
Type: article
Authors: Sanna, A.; Reid, M. J.; Menten, K. M.; Dame, T. M.; Zhang, B.; Sato, M.; Brunthaler, A.; Moscadelli, L.; Immer, K.
Abstract: We report four trigonometric parallaxes for high-mass star-forming regions within 4 kpc of the Galactic center. These measurements were made with the Very Long Baseline Array as part of the BeSSeL Survey. By associating these sources kinematically with large-scale features in CO and H I longitude-velocity diagrams, we begin to outline some major features of the inner Milky Way: the Connecting arm, the near and far 3 kpc arms, and the Norma arm. The Connecting arm in the first Galactic quadrant lies closer to the Galactic center than the far 3 kpc arm and is offset by the long-bar's major axis near its leading edge, supporting the presence of an inner Lindblad resonance. Assuming the 3 kpc arms are a continuous physical structure, the relative Galactocentric distance of its near and far sides suggests highly elliptical streamlines of gas around the bar(s) and a bar corotation radius, r CR >~ 3.6 kpc. At a Galactic longitude near 10° and a heliocentric distance of about 5 kpc, the near 3 kpc arm and the Norma arm intersect on a face-on view of our Galaxy, while passing at different Galactic latitudes. We provide an accurate distance measurement to the W 31 star-forming complex of 4.95^{+0.51}_{-0.43} kpc from the Sun, which associates it with a bright CO feature belonging to the near 3 kpc arm.
Trigonometric Parallaxes of Star Forming Regions in the Scutum Spiral ArmSato, M.Wu, Y. W.Immer, K.Zhang, B.Sanna, A.Reid, M. J.Dame, T. M.Brunthaler, A.Menten, K. M.DOI: info:10.1088/0004-637X/793/2/72v. 79372
Sato, M., Wu, Y. W., Immer, K., Zhang, B., Sanna, A., Reid, M. J., Dame, T. M., Brunthaler, A., and Menten, K. M. 2014. "Trigonometric Parallaxes of Star Forming Regions in the Scutum Spiral Arm." The Astrophysical Journal 793:72. https://doi.org/10.1088/0004-637X/793/2/72
ID: 131122
Type: article
Authors: Sato, M.; Wu, Y. W.; Immer, K.; Zhang, B.; Sanna, A.; Reid, M. J.; Dame, T. M.; Brunthaler, A.; Menten, K. M.
Abstract: We report measurements of trigonometric parallaxes for six high-mass star-forming regions in the Scutum spiral arm of the Milky Way as part of the BeSSeL Survey. Combining our measurements with 10 previous measurements from the BeSSeL Survey yields a total sample of 16 sources in the Scutum arm with trigonometric parallaxes in the Galactic longitude range from 5° to 32°. Assuming a logarithmic spiral model, we estimate a pitch angle of 19.°8 ± 3.°1 for the Scutum arm, which is larger than pitch angles reported for other spiral arms. The high pitch angle of the arm may be due to the arm's proximity to the Galactic bar. The Scutum arm sources show an average peculiar motion of 4 km s-1 slower than the Galactic rotation and 8 km s-1 toward the Galactic center. While the direction of this non-circular motion has the same sign as determined for sources in other spiral arms, the motion toward the Galactic center is greater for the Scutum arm sources.