Oct 24, 2001 The Gould Belt and other large star forming complexes 1 Young stars in the nearest solar neighbourhood Young stars in the nearest solar neighbourhood David Fernández, Francesca Figueras, Jordi Torra Departament d’Astronomia i Meteorologia Universitat de Barcelona
Young stars in the nearest solar neighbourhood. David Fernández, Francesca Figueras, Jordi Torra Departament d’Astronomia i Meteorologia Universitat de Barcelona. Stellar trajectories. Observations:. Theory:. The young stellar component. Models. Gas & diffuse X-ray distribution. - PowerPoint PPT Presentation
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Oct 24, 2001 The Gould Belt and other large star forming complexes 1
Young stars in the nearest solar neighbourhood
Young stars in the nearest solar neighbourhood
David Fernández, Francesca Figueras, Jordi Torra
Departament d’Astronomia i Meteorologia
Universitat de Barcelona
Oct 24, 2001 The Gould Belt and other large star forming complexes 2
Young stars in the nearest solar neighbourhood
The young stellar component
Gas & diffuse X-ray distribution
Models
Work in progress, Fernández PhD thesis
Observations: Theory:
Stellar trajectories
Oct 24, 2001 The Gould Belt and other large star forming complexes 3
Young stars in the nearest solar neighbourhood
Individual objects (Hipparcos data):
• T Tauri stars (Frink 1998)
• O-B stars (Fernández 1998, Torra et al. 2000)
• X-ray G5 V stars (age from Lx)
Groups:
• Young local associations (compilation, several authors)
• OB associations (de Zeeuw et al. 1999)
• Moving groups (Asiain et al. 1999)
The young stellar component in the solar neighbourhood
Oct 24, 2001 The Gould Belt and other large star forming complexes 4
Young stars in the nearest solar neighbourhood
Gas & diffuse X-ray distribution in the solar neighbourhood (I)
Local bubble (LB):
Low density (~0.005 cm-3) region filled with hot gas (~106 K), responsible for an important fraction of the 1/4 keV emission (soft X-rays)
Not completely filled? Local cavity + Local bubble
Snowden et al. (1998), Egger (1998): Distribution of the diffuse soft X-ray background
Sfeir et al. (1999): Distribution of the neutral gas in the LISM (X,Y), (X,Z), (Y,Z) maps Elongated to high galactic latitudes, and tilted perpendicular to the Gould Belt’s plane
Oct 24, 2001 The Gould Belt and other large star forming complexes 5
Young stars in the nearest solar neighbourhood
Loop I & Local bubble:
Loop I is still an active superbubble, hotter (2.5·106 K) and denser (0.015 cm-2) than the LB Pressure higher than in the LB
HI “wall” (NH > 1020 cm-2) between both at R ~ 40 pc
Breitschwerdt et al. (2000): Study of the hydromagnetic instability caused by the interaction between the LB and Loop I
Schematic representation of the interaction
Other bubbles:
Heiles (1998): GSH 238+00+09 major superbubble toward l ~ 238o
Gas & diffuse X-ray distribution in the solar neighbourhood (II)
Oct 24, 2001 The Gould Belt and other large star forming complexes 6
Young stars in the nearest solar neighbourhood
Olano (1982):
Gould Belt as an expanding ring of gas
Pöppel & Marronetti (2000):
Explosive event 35 Myr ago at R ~ 120 pc, (l,b) ~ (140º,16º) (Olano’s model 1) consistent with kinematics of CNM
Inclusion of three young disturbance centers in the model: Orion, Hercules and Loop I
Olano (2001):
The origin of the local system of gas and stars rotating supercloud ~2·107 M and ~400 pc
Sirius supercluster (500 Myr ago) + Gould Belt + Local arm (after collision with a main spiral arm 100 Myr ago)
Some models in the literature
Oct 24, 2001 The Gould Belt and other large star forming complexes 7
Young stars in the nearest solar neighbourhood
Galactic potential:
• General axisymmetric potential (Allen & Santillán 1991)
Bulge + disk + halo (Ro= 8.5 kpc, o= 220 km s-1)
• Spiral arm perturbation (Fernández et al. 2001):
p= 30 km s-1 kpc-1 ; i = -6o, m = 2, = 330o
• Central bar potential (triaxial ellipsoid, Palous et al. 1993):
b = 70 km s-1 kpc-1
Method:
Integration of the equations of motion (fourth order Runge-Kutta)
Coordinates:
(): Rotating Local Standard of Rest
Stellar trajectories
Oct 24, 2001 The Gould Belt and other large star forming complexes 8
Young stars in the nearest solar neighbourhood
OB associations in Scorpius-Centaurus
Relation with Loop I superbubble (age ~ 10 Myr): stellar winds and supernovae
Responsible for the origin of the Local Bubble? (Maíz-Apellániz 2001, Berghöfer & Breitschwerdt 2001)
Data from de Zeeuw et al. (1999):
Associació Position Number of members
Age (U,V,W)hel
Upper Scorpius (US)
R ~ 145 pc
(l,b) ~ (350º,20º)
120
ST:B-M
~5 Myr (-4.7,-16.8,-6.7)
Upper Centaurus Lupus (UCL)
R ~ 140 pc
(l,b) ~ (330º,15º)
221
ST: B-M
~13 Myr (-3.9,-20.3,-3.4)
Lower Centaurus Crux (LCC)
R ~ 118 pc
(l,b) ~ (300º,5º)
180
ST: B-M
~10 Myr (-8.8,-20.0,-6.2)
Oct 24, 2001 The Gould Belt and other large star forming complexes 9
Young stars in the nearest solar neighbourhood
Evolution of the OB associations in Scorpius-Centaurus (I)
(-15) -age < t < 0 Myr
LCC
UCL
US
Orbits very similar to Maíz-Apellániz (2001), although in our case they concentrate more in space
Expected number of past SNe:
LCC 6
UCL 13
US 1
SNe of LCC responsible for the creation of the LB
But there is a great spatial asymmetry (too much?)
Olano’s model
t = -31 Myr
t = -20 Myr
t= -10 Myr
Present
Oct 24, 2001 The Gould Belt and other large star forming complexes 10
Young stars in the nearest solar neighbourhood
Evolution of the OB associations in Scorpius-Centaurus (II)
(-15) -age < t < 0 Myr
LCC
UCL
US A little confusing projection since the associations are not placed on the () plane
UCL and US are not so distant from the LB!
Oct 24, 2001 The Gould Belt and other large star forming complexes 11
Young stars in the nearest solar neighbourhood
Evolution of the Pleiades moving group
The youngest moving group in the solar neighbourhood
Substructures found in Asiain et al. (1999):
Hipparcos data (O-B-A stars) + non parametric technics (U,V,W,age)
U (km/s) V(km/s) W(km/s) Age (Myr) Number of objects
B1 -4.5(4.7) -20.1(3.3) -5.5(1.9) 20 (10) 34
B2 -10.7(5.3) -18.8(3.7) -5.6(2.2) 60 (20) 75
B3 -16.8(5.1) -21.7(2.7) -5.6(4.6) 300(120) 50
B4 -8.7(4.8) -26.4(3.3) -8.5(4.7) 150 (50) 53
B1: composed by Sco-Cen OB association members
B2: seems to be the superposition of several OB associations from the Gould Belt
B3 and B4:birthplace close to the minimum of the spiral arm potential
Oct 24, 2001 The Gould Belt and other large star forming complexes 12
Young stars in the nearest solar neighbourhood
Evolution of the B2 substructure - Pleiades MG (I)
t = 0 (at present)
Olano’s model
(t = 0)
Oct 24, 2001 The Gould Belt and other large star forming complexes 13
Young stars in the nearest solar neighbourhood
Evolution of the B2 substructure - Pleiades MG (II)
t = -10 Myr
Olano’s model
(t = -10 Myr)
Oct 24, 2001 The Gould Belt and other large star forming complexes 14
Young stars in the nearest solar neighbourhood
Evolution of the B2 substructure - Pleiades MG (III)
t = -20 Myr
Olano’s model
(t = -20 Myr)
Oct 24, 2001 The Gould Belt and other large star forming complexes 15
Young stars in the nearest solar neighbourhood
Evolution of the B2 substructure - Pleiades MG (IV)
Olano’s model
(t = -31 Myr)
t = -30 Myr
Oct 24, 2001 The Gould Belt and other large star forming complexes 16
Young stars in the nearest solar neighbourhood
Evolution of the B1 + B2 substructures (Pleiades MG)
Kernel function of the superposition of orbits B1 + B2 individual members back on time
Center at (x,y) = (60,10)
R = 61 pc, l = 10o
Pöppel’s model (2001):
Single isotropic disturbance centers:
- Orion (R,l,b) = (200, 195,-40)
- Hercules (R,l,b) = (145, 45, 35)
- Loop I (R,l,b) = (210, 330, 35)
GC
GR
Oct 24, 2001 The Gould Belt and other large star forming complexes 17