Young stars raining through the galactic halo: the nature and orbit of price-whelan 1

ABSTRACT We present radial velocities for five member stars of the recently discovered young (age ≃ 100−150 Myr) stellar system Price-Whelan 1 (PW 1), which is located far away in the Galactic Halo (D≃ 29 kpc, Z≃ 15 kpc), and that is probably associated with the leading arm (LA) of the Magellanic Stream. We measure the systemic radial velocity of PW 1, Vr = 275 ± 10 km s−1, significantly larger than the velocity of the LA gas in the same direction. We re-discuss the main properties and the origin of this system in the light of these new observations, computing the orbit of the system and comparing its velocity with that of the H i in its surroundings. We show that the bulk of the gas at the velocity of the stars is more than 10 deg (5 kpc) away from PW 1 and the velocity difference between the gas and the stars becomes larger as gas closer to the stars is considered. We discuss the possibilities that (1) the parent gas cloud was dissolved by the interaction with the Galactic gas, and (2) that the parent cloud is the high-velocity cloud (HVC) 287.5+22.5 + 240, lagging behind the stellar system by ≃ 25 km s−1 and ≃10 deg ≃ 5 kpc. This HVC, which is part of the LA, has metallicity similar to PW 1, displays a strong magnetic field that should help to stabilize the cloud against ram pressure, and shows traces of molecular hydrogen. We also show that the system is constituted of three distinct pieces that do not differ only by position in the sky but also by stellar content.

Download Full-text

The ‘High Velocity Cloud’ Origin of the Magellanic System

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000021755 ◽

1987 ◽

Vol 7 (1) ◽

pp. 19-25 ◽

Cited By ~ 31

Author(s):

D. S. Mathewson ◽

S. R. Wayte ◽

V. L. Ford ◽

K. Ruan

Keyword(s):

High Velocity ◽

Galactic Halo ◽

Magellanic Clouds ◽

The One ◽

Magellanic Stream ◽

Gaseous Halo ◽

Velocity Cloud ◽

High Velocity Cloud ◽

Magellanic System

AbstractIt is believed that the splitting of the SMC into two fragments and the production of the Inter-Cloud gas and the Magellanic Stream occurred in the one event 4 × 108 years ago. This event was a collision between the LMC and SMC. This time is too short for the Stream to be tidal, or be the result of stripping of the Inter-Cloud gas by a diffuse gaseous halo. It is proposed that the clouds in the Stream are the results of collisions between the Inter-Cloud gas and HVCs in the Galactic halo. A model of this process accounts for all of the observational features of the Stream. Observations of HVCs in the path of the Magellanic Clouds are used to predict the development of the Stream. The HVCs in our halo are thought to be a result of a collision of a galaxy with our Galaxy 6 × 109 years ago.

Download Full-text

The Kinematics of the Magellanic Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900228180 ◽

1995 ◽

Vol 166 ◽

pp. 273-282

Author(s):

B.E. Westerlund

Keyword(s):

Galactic Halo ◽

Neutral Hydrogen ◽

Magellanic Clouds ◽

Great Promise ◽

Common Envelope ◽

The Past ◽

Ram Pressure ◽

Long Time ◽

Magellanic Stream ◽

Magellanic System

It is essential for our understanding of the evolution of the Magellanic System, comprising the Large and the Small Magellanic Cloud, the Intercloud or Bridge region and the Magellanic Stream, to know its motions in the past. The Clouds have a common envelope of neutral hydrogen; this indicates that they have been bound to each others for a long time. The Magellanic System moves in the gravitational potential of our Galaxy; it is exposed to ram pressure through its movement in the galactic halo. Both effects ought to be noticeable in their present structure and kinematics. It is generally assumed, but not definitely proven, that the Clouds have been bound to our Galaxy for at least the last 7 Gyr. Most models assume that the Clouds lead the Magellanic Stream. The interaction between the Clouds has influenced their structure and kinematics severely. The effects should be possible to trace in the motions of their stellar and gaseous components as pronounced disturbances. Recent astrometric contributions in this field show a great promise for the future if still higher accuracy can be achieved.

Download Full-text

The Galactic Halo Ionising Field

Publications of the Astronomical Society of Australia ◽

10.1071/as97059 ◽

1997 ◽

Vol 14 (1) ◽

pp. 59-63 ◽

Cited By ~ 9

Author(s):

J. Bland-Hawthorn ◽

P. R. Maloney

Keyword(s):

Galactic Halo ◽

Galactic Disk ◽

Line Emission ◽

Young Stars ◽

Star Forming ◽

Star Forming Regions ◽

Optical Line ◽

The Mean ◽

Alternative Sources ◽

Magellanic Stream

AbstractThere has been much debate in recent decades as to what fraction of ionising photons from star-forming regions in the Galactic disk escape into the halo. The recent detection of the Magellanic Stream in optical line emission at the CTIO 4 m and the AAT 3·9 m telescopes may now provide the strongest evidence that at least some of the radiation escapes the disk completely. We present a simple model to demonstrate that, while the distance to the Magellanic Stream is uncertain, the observed emission measures (εm ≈ 0·5 – 1 cm−6 pc) are most plausibly explained by photoionisation due to hot, young stars. This model requires that the mean Lyman-limit opacity perpendicular to the disk is τLL ≈ 3, and the covering fraction of the resolved clouds is close to unity. Alternative sources (e.g. shock, halo, LMC or metagalactic radiation) contribute negligible ionising flux.

Download Full-text

HI and Hot Gas in the Outskirts of the M81 Group

Symposium - International Astronomical Union ◽

10.1017/s0074180900198171 ◽

2004 ◽

Vol 217 ◽

pp. 452-457 ◽

Cited By ~ 5

Author(s):

M. Bureau ◽

F. Walter ◽

J. van Gorkom ◽

C. Carignan

Keyword(s):

High Resolution ◽

Column Density ◽

Dwarf Galaxies ◽

Star Forming ◽

Hot Gas ◽

External Group ◽

Ram Pressure ◽

Tidal Tails ◽

Velocity Cloud ◽

High Velocity Cloud

Results are presented from a wide area, high resolution HI synthesis survey of the outer regions of the nearby M81 group, where internal (galactic) and external (group-related) evolution processes can be studied simultaneously in great detail. The survey encompasses the star forming dwarf galaxies M81dwA, UGC4483, and HoII, where evidence of ram pressure stripping was recently discovered. The data do not reveal any intergalactic HI, but the outer parts of HoII are reminiscent of tidal tails. We argue however that those structures are equally consistent with the latest ram pressure models including cooling. The case for a hot intergalactic medium in this poor, spiral-only group is thus still open. The survey also puts tight constraints on possible counterparts to the local high velocity cloud population in an external group, reaching a 3σ column density of 1019 atom cm−2 and a 6σ limiting mass of 1.5 × 105M⊙.

Download Full-text

Nature of a shell of young stars in the outskirts of the Small Magellanic Cloud

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936021 ◽

2019 ◽

Vol 631 ◽

pp. A98 ◽

Cited By ~ 3

Author(s):

David Martínez-Delgado ◽

Anna Katherina Vivas ◽

Eva K. Grebel ◽

Carme Gallart ◽

Adriano Pieres ◽

...

Keyword(s):

Stellar System ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Young Stars ◽

Optical Data ◽

Small Magellanic Cloud ◽

Stellar Content ◽

North East ◽

The North ◽

Spiral Arm

Context. Understanding the evolutionary history of the Magellanic Clouds requires an in-depth exploration and characterization of the stellar content in their outer regions, which ultimately are key to tracing the epochs and nature of past interactions. Aims. We present new deep images of a shell-like overdensity of stars in the outskirts of the Small Magellanic Cloud (SMC). The shell, also detected in photographic plates dating back to the fifties, is located at ∼1.9° from the center of the SMC in the north-east direction. Methods. The structure and stellar content of this feature were studied with multiband, optical data from the Survey of the MAgellanic Stellar History (SMASH) carried out with the Dark Energy Camera on the Blanco Telescope at Cerro Tololo Inter-American Observatory. We also investigate the kinematic of the stars in the shell using the Gaia Data Release 2. Results. The shell is composed of a young population with an age ∼150 Myr, with no contribution from an old population. Thus, it is hard to explain its origin as the remnant of a tidally disrupted stellar system. The spatial distribution of the young main-sequence stars shows a rich sub-structure, with a spiral arm-like feature emanating from the main shell and a separated small arc of young stars close to the globular cluster NGC 362. We find that the absolute g-band magnitude of the shell is Mg, shell = −10.78 ± 0.02, with a surface brightness of μg, shell = 25.81 ± 0.01 mag arcsec−2. Conclusion. We have not found any evidence that this feature is of tidal origin or a bright part of a spiral arm-like structure. Instead, we suggest that the shell formed in a recent star formation event, likely triggered by an interaction with the Large Magellanic Cloud and or the Milky Way, ∼150 Myr ago.

Download Full-text

A confirmed location in the Galactic halo for the high-velocity cloud ‘chain A’

Nature ◽

10.1038/22061 ◽

1999 ◽

Vol 400 (6740) ◽

pp. 138-141 ◽

Cited By ~ 75

Author(s):

Hugo van Woerden ◽

Ulrich J. Schwarz ◽

Reynier F. Peletier ◽

Bart P. Wakker ◽

Peter M. W. Kalberla

Keyword(s):

High Velocity ◽

Galactic Halo ◽

Velocity Cloud ◽

High Velocity Cloud

Download Full-text

A Search for Tidal Stellar Debris from the Magellanic Clouds: Survey Results from the First Two Years

Symposium - International Astronomical Union ◽

10.1017/s007418090011873x ◽

1999 ◽

Vol 190 ◽

pp. 508-510 ◽

Cited By ~ 8

Author(s):

S. R. Majewski ◽

J. C. Ostheimer ◽

W. E. Kunkel ◽

K. V. Johnston ◽

R. J. Patterson ◽

...

Keyword(s):

Globular Clusters ◽

Main Sequence ◽

Galactic Halo ◽

Large Magellanic Cloud ◽

Main Sequence Stars ◽

Tidal Disruption ◽

Negative Results ◽

Ram Pressure ◽

Survey Results ◽

Magellanic Stream

An important discriminant between leading models for the origin of the Magellanic Stream is the presence of a stellar counterpart to the HI gas stream: ram pressure stripping of gas by a putative hot Galactic halo would act only on Magellanic gas while gravitational tidal stripping would act on both gas and stars. Several previous attempts to find tidal stellar debris have failed to find carbon stars, A stars, or other main sequence stars in the Magellanic Stream (Mathewson et al. 1979; Recillas-Cruz 1982; Brück & Hawkins 1983; Guhathakurta & Lin 1999). However, there has long been a suggestion (Kunkel 1979; Lynden-Bell 1982) of a possible Magellanic association of satellite galaxies and globular clusters that have similar orbits and may derive from the break up of a greater Magellanic galaxy (Lynden-Bell & Lynden-Bell 1995; Majewski et al. 1997). Recent models (Moore & Davis 1994; Johnston 1998) of the tidal disruption of Large Magellanic Cloud (LMC)-like systems indicate a wide dispersal of debris, much wider than the rather confined HI stream, so that the contrast of tidal debris against the Galactic fore/background would be low. If true, this could explain some of the previous negative results for tidal debris searches.

Download Full-text

A COMPACT HIGH VELOCITY CLOUD NEAR THE MAGELLANIC STREAM: METALLICITY AND SMALL-SCALE STRUCTURE

The Astrophysical Journal ◽

10.1088/0004-637x/800/1/44 ◽

2015 ◽

Vol 800 (1) ◽

pp. 44 ◽

Cited By ~ 4

Author(s):

Nimisha Kumari ◽

Andrew J. Fox ◽

Jason Tumlinson ◽

Christopher Thom ◽

Tobias Westmeier ◽

...

Keyword(s):

High Velocity ◽

Scale Structure ◽

Small Scale ◽

Small Scale Structure ◽

Magellanic Stream ◽

Velocity Cloud ◽

High Velocity Cloud

Download Full-text

The Metallicity and Dust Content of HVC287+22+240: Evidence for a Magellanic Clouds Origin

Symposium - International Astronomical Union ◽

10.1017/s0074180900118728 ◽

1999 ◽

Vol 190 ◽

pp. 506-507

Author(s):

Bart Wakker ◽

Blair D. Savage ◽

Limin Lu ◽

Wallace L.W. Sargent ◽

Kenneth R. Sembach ◽

...

Keyword(s):

High Velocity ◽

Magellanic Clouds ◽

Dust Content ◽

Present Evidence ◽

Tidal Interaction ◽

Magellanic Stream ◽

Velocity Cloud ◽

High Velocity Cloud

We present evidence that the properties of the high-velocity cloud catalogued as #187 by Wakker & van Woerden (1991) (HVC287+22+240) can be explained if it is part of a leading arm counterpart of the Magellanic Stream, and we use this to argue that the HVC originated in the Magellanic Clouds after a tidal interaction.

Download Full-text