The proper motion of the Local Group galaxy IC 10

Brunthaler, A.; Reid, M. J.; Falcke, H.; Henkel, C.; Menten, K. M.

doi:10.1051/0004-6361:20066430

Cited by 77 publications

(87 citation statements)

References 47 publications

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“…With state-of-the-art analysis methods, using background galaxies as a stationary reference frame, we achieved a final PM accuracy of ∼12 μas yr −1 . This is comparable to the accuracies that have been achieved for other Local Group galaxies using VLBA observations of water masers (Brunthaler et al 2005(Brunthaler et al , 2007. Water masers were recently discovered in M31 (Darling 2011), but have yet to be used for a PM determination.…”

Section: Discussionsupporting

confidence: 81%

“…This is well beyond the accuracy limit of current ground-based optical observations, even for long time baselines (e.g., >40 year; e.g., Vieira et al 2010). The two most accurate (∼0.01 mas yr −1 ) PM measurements in the Local Group come from studies of water masers in M33 (Brunthaler et al 2005) and IC 10 (Brunthaler et al 2007). However, water masers in M31 have only recently been discovered (Darling 2011), and it will take time until a sufficient baseline has been established to enable PM measurements.…”

Section: Introductionmentioning

confidence: 99%

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THE M31 VELOCITY VECTOR. I.HUBBLE SPACE TELESCOPEPROPER-MOTION MEASUREMENTS

Sohn¹,

Anderson²,

Marel³

2012

ApJ

125

183

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We present the first proper-motion (PM) measurements for the galaxy M31. We obtained new V-band imaging data with the Hubble Space Telescope ACS/WFC and the WFC3/UVIS instruments of three fields: a spheroid field near the minor axis, an outer disk field along the major axis, and a field on the Giant Southern Stream. The data provide five to seven year time baselines with respect to pre-existing deep first-epoch observations of the same fields. We measure the positions of thousands of M31 stars and hundreds of compact background galaxies in each field. High accuracy and robustness is achieved by building and fitting a unique template for each individual object. The average PM for each field is obtained from the average motion of the M31 stars between the epochs with respect to the background galaxies. For the three fields, the observed PMs (μ W , μ N ) are, in units of mas yr −1 , (−0.0458, −0.0376) ± (0.0165, 0.0154), (−0.0533, −0.0104) ± (0.0246, 0.0244), and (−0.0179, −0.0357) ± (0.0278, 0.0272), respectively. The ability to average over large numbers of objects and over the three fields yields a final displacement accuracy of a few thousandths of a pixel, corresponding to only 12 μas yr −1 . This is comparable to what has been achieved for other Local Group galaxies using Very Long Baseline Array observations of water masers. Potential systematic errors are controlled by an analysis strategy that corrects for detector charge transfer inefficiency, spatially and time-dependent geometric distortion, and point-spread function variations. The robustness of the PM measurements and uncertainties are supported by the fact that data from different instruments, taken at different times and with different telescope orientations, as well as measurements of different fields, all yield statistically consistent results. Papers II and III of this series explore the implications of the new measurements for our understanding of the history, future, and mass of the Local Group.

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Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

THE M31 VELOCITY VECTOR. I.HUBBLE SPACE TELESCOPEPROPER-MOTION MEASUREMENTS

Sohn¹,

Anderson²,

Marel³

2012

ApJ

125

183

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“…3). We observed the usually brightest maser in IC 10-SE with the VLBA thirteen times between February 2001 and June 2005 [28].…”

Section: Towards a Kinematic Model Of The Local Groupmentioning

confidence: 71%

“…These regions can be excluded, since the stellar disk of M33 shows no signs of such interactions. Taken from [28].…”

Section: Discussionmentioning

confidence: 99%

Towards a kinematic model of the Local Group

Brunthaler¹,

Reid²,

Falcke³

et al. 2007

Proceedings of 8th European VLBI Network Symposium — PoS(8thEVN)

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Measuring the proper motions and geometric distances of galaxies within the Local Group is very important for our understanding of its history, present state and future. Currently, proper motion measurements using optical methods are limited only to the closest companions of the Milky Way. However, given that VLBI provides the best angular resolution in astronomy and phasereferencing techniques yield astrometric accuracies of ≈ 10 micro-arcseconds, measurements of proper motions and angular rotation rates of galaxies out to a distance of ∼ 1 Mpc are feasible. This article presents results of VLBI observations of regions of H 2 O maser activity in the Local Group galaxies M33 and IC 10. Two masing regions in M33 are on opposite sides of the galaxy. This allows a comparison of the angular rotation rate (as measured by the VLBI observations) with the known inclination and rotation speed of the HI gas disk leading to a determination of a geometric distance of 730 ± 100 ± 135 kpc. The first error indicates the statistical error of the proper-motion measurements, while the second error is the systematic error of the rotation model. Within the errors, this distance is consistent with the most recent Cepheid distance to M33. Since all position measurements were made relative to an extragalactic background source, the proper motion of M33 has also been measured. This provides a three dimensional velocity vector of M33, showing that this galaxy is moving with a velocity of 190 ± 59 km s −1 relative to the Milky Way. For IC 10, we obtain a motion of 215 ± 42 km s −1 relative to the Milky Way. These measurements promise a new handle on dynamical models for the Local Group and the mass and dark matter halo of Andromeda and the Milky Way.8th European VLBI Network Symposium

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“…Water masers are the main targets, and these exist only in the few LG galaxies with high star formation rates. PM measurements have been reported for M33 and IC10, both satellites of M31 (Brunthaler et al 2005(Brunthaler et al , 2007. In the future, such measurements may become possible also for, e.g., M31 (Darling 2011) and the Magellanic Clouds.…”

Section: Observational Approaches and Future Prospectsmentioning

confidence: 97%

Local Group Proper Motion Dynamics

Marel

2014

Proc. IAU

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Abstract. Our knowledge of the dynamics and masses of galaxies in the Local Group has long been limited by the fact that only line-of-sight velocities were observationally accessible. This introduces significant degeneracies in dynamical models, which can only be resolved by measuring also the velocity components perpendicular to the line of sight. However, beyond the solar neighborhood, the corresponding proper motions have generally been too small to measure. This has changed dramatically over the past decade, especially due to the angular resolution and stability available on the Hubble Space Telescope. Proper motions can now be reliably measured throughout the Local Group, as illustrated by, e.g., the work of the HSTPROMO collaboration. In this review, I summarize the importance of proper motions for Local Group science, and I describe the current and future observational approaches and facilities available to measure proper motions. I highlight recent results on various Milky Way populations (globular clusters, the bulge, the metal-poor halo, hypervelocity stars, and tidal streams), dwarf satellite galaxies, the Magellanic Clouds and the Andromeda System.

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The proper motion of the Local Group galaxy IC 10

Cited by 77 publications

References 47 publications

THE M31 VELOCITY VECTOR. I.HUBBLE SPACE TELESCOPEPROPER-MOTION MEASUREMENTS

THE M31 VELOCITY VECTOR. I.HUBBLE SPACE TELESCOPEPROPER-MOTION MEASUREMENTS

Towards a kinematic model of the Local Group

Local Group Proper Motion Dynamics

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