t. girardstars: young, old and variable – may 18-21, 2014 t. girard yale university the glint on...
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T. GirardStars: Young, Old and Variable – May 18-21, 2014
T. GirardYale University
The Glint on Magellan's Prow:
Young Stars in the Leading Arm
of the Magellanic Stream______________________________________________________
T. GirardStars: Young, Old and Variable – May 18-21, 2014
“Score Machine” Ames city-league softball, ~ early 1980’s
T. GirardStars: Young, Old and Variable – May 18-21, 2014
A more relevant team... Casetti-Dinescu et al. 2014, (ApJL 784, 37)“Recent Star Formation in the Leading Arm of the
Magellanic Stream”
Christian Moni Bidin Univ. Catolica del Norte, Antofagasta, Chile
Dana Casetti SCSU & Yale University
Rene Mendez Universidad de Chile Santiago, Chile
Kathy Vieira CIDA Merida, Venezuela
Vladimir Korchagin Southern Federal UniversityRostov-on-Don, Russia
Bill van Altena Yale University
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Location, location, location…
credit: www.eso.org – Yuri Beletsky
T. GirardStars: Young, Old and Variable – May 18-21, 2014
“a conglomerate of stars put together in a manner of two clouds”
Antonio Pigafetta (1524)
Magellanic Clouds:
Over the Edge of the World by Laurence Bergreen
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: The Gaseous Stream
Nidever et al. 2010 Figure 9. Magellanic Stream and Clouds in HI (red) with an optical all-sky image (blue, white, and brown; Mellinger 2009) in Aitoff projection with the direction to the Galactic Center at the center.
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: The Gaseous Stream
Nidever et al. 2008
Gas velocity
Gas density
Model constraints:
Reproduce the various components of the gaseous Magellanic Stream; spatial and 1D velocity distribution.
Reproduce the current locations and 3D velocities of the Clouds.
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: Orbits & Interaction
“New” orbit: HST-based , Kallivayalil et al. 2006
Old orbit: (based on matching MS, spatially)
MW-Clouds interaction is currently under dispute!
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: Modeling the Interaction
Diaz & Bekki (2012)
SMC: N-body LMC, MW: rigid potentials
Cloud-cloud interaction:1st encounter:
~2 Gyr ago, MS formation
2nd encounter: ~200 Myr ago, Bridge formation
MW-Clouds interaction:1st pericenter passage:
~2.5 Gyr ago2nd pericenter passage:
now
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: Modeling the Interaction
Diaz & Bekki (2012)
SMC: N-body LMC, MW: rigid potentials
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: Modeling the Interaction
Diaz & Bekki 2012 (model) Nidever et al. 2010 (observations)
Radial velocity distribution
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: Modeling the Interaction
Diaz & Bekki 2012, Nidever et al. 2010
Spatial distribution:
MS, LA, Bridge are of tidal origin, primarily material pulled out from the SMC.
LA is poorly explained by all models; gas hydrodynamics most likely plays a role.
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Magellanic Clouds: LMC Absolute Proper Motion
Diaz (2013, personal communication)
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Star Search: A Cross-Catalog Approach
Photometry
Astrometry/Photometry
GALEX DR5 (Bianchi et al. 2011)
2MASS (Skrutskie et al. 2006)
APASS (Henden et al. 2011)
NUV
J
V
all-sky1771-2831Å, eff = 2315.7Å, NUVlim= 20.8
all-sky (also made use of 6x2MASS)
AAVSO all-sky survey (B,V, g, r, i) 10 < V < 17.0, V ~ 0.06 mag
SPM4 (Girard et al. 2011)
, V < -20o, Vlim~17.5V ~ 0.05 mag
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Star Search: A Cross-Catalog Approach
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Star Search: A Cross-Catalog Approach
-2.0 ≤ (NUV-V)0 ≤ 0.0
-1.2 ≤ (V-J)0 ≤ -0.2
(NUV ≤ 0.10, J ≤ 0.15)
≤ 8.0 mas/yr
( ≤ 4.0 mas/yr)
13.0 ≤ V0 ≤ 17.0
E(B-V) ≤ 0.5
Final Selection Criteria
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Results:
567 OB-type star candidates(from an initial ~4 million)
Casetti-Dinescu et al. 2012
HI density
(Nidever et al. 2010)
OB-type Star Search: A Cross-Catalog Approach
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB star candidates include
• a well-populated SMC wing, extending in a narrow band toward the LMC to RA ~ 3.4h, possibly reaching to the LMC;
• two branches partially surrounding the SMC;
• well-defined concentrations at the ends of the LMC bar, and a well-populated LMC periphery;
• several groupings in the LA;
• a few scattered candidates in the MS.
OB-type Star Search: The Extended Clouds Region
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Star Search: The Extended Clouds Region
OB star candidates include
• a well-populated SMC wing, extending in a narrow band toward the LMC to RA ~ 3.4h, possibly reaching to the LMC;
• two branches partially surrounding the SMC;
• well-defined concentrations at the ends of the LMC bar, and a well-populated LMC periphery;
• several groupings in the LA;
• a few scattered candidates in the MS.
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Stars in the Leading Arm: Spectroscopic Follow-up
Obtained spectra of 42 candidates in the Leading Arm, in April 2013
IMACS on 6.5m Baade telescope,1 Å resolution, 3700-5300 Å range
Spectral Type, RV, log g, Teff
( υsini, log[NHe/NH] )
Twin 6.5m Magellan telescopes: Baade and Clay Las Campanas, Chile
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Stars in the Leading Arm: Spectroscopic Findings
= fast rotator
Casetti-Dinescu et al. 2014
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Stars in the Leading Arm: Spectroscopic Findings
Found 19 young, massive stars, including...
five with RVs consistent with Leading Arm membership;
plus
one O6V star, i.e., ~40 M and very young (~1 Myr).
Casetti-Dinescu et al. 2014
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Stars in the Leading Arm: Stars of Interest
ID RV (kms)
vsini (kms)
Teff (K)
log g log[NHeNH
]Sp.Type
B.02 168 ± 4 [ 0 ] 16000 ± 400
3.76 ± 0.09
[ -1 ] B4III
B.03 229 ± 5 [ 0 ] 17500 ± 1100
3.86 ± 0.18
-1.60 ± 0.18
B3IV
B.14 207 ± 5 300 15800 ± 700
3.60 ± 0.15
[ -1 ] B4/5III
B.15 248 ± 5 [ 0 ] 14800 ± 700
4.17 ± 0.15
-2.10 ± 0.33
sdB
A.15 166 ± 6 280 13400 ± 600
3.67 ± 0.18
[ -1 ] B7III
A.19 234 ± 6 260 17200 ± 1900
4.03 ± 0.36
-1.58 ± 0.42
B3IV
A.08 71 ± 11
[ 0 ] 43700 ± 1200
4.47 ± 0.12
-1.20 ± 0.39
O6V
T. GirardStars: Young, Old and Variable – May 18-21, 2014
OB-type Stars in the Leading Arm: Spectroscopic Findings
For the five young, LA members (RV>150 km/s)...
Distances are ~20 kpc from the Sun, (or ~18 kpc from the Galactic center, i.e. roughly the extent of the Galactic disk).
Ages are ~100 Myr, i.e. recently formed.
Gray band is kinematical distance to a particular high-velocity cloud in the LA. (McClure-Griffiths et al. 2008)
= RV>150km/s, = O6V star Casetti-Dinescu et al. 2014
T. GirardStars: Young, Old and Variable – May 18-21, 2014
Summary:
Young, massive stars have been found in the Leading Arm of the gaseous Magellanic Stream
Their location suggests recent interaction of gas in the Leading Arm with that of the outer edge of the Milky Way
Implying that hydrodynamical effects are at play and must be included in Clouds/MW interaction models
A single, more distant and extremely massive/young O6V star also has been identified, unquestionably formed in situ
Stay tuned for more...
T. GirardStars: Young, Old and Variable – May 18-21, 2014
And a little press is always nice...