H2 based Star Formation - Progress...
Transcript of H2 based Star Formation - Progress...
H2 based Star Formation -
Progress Report
with Frazer Pearce, Inti Pelupessy, Padelis Papadopoulos, Paul Torrey
Hanni Lux
Outline | SubGrid ISM
Final Goal:
Run a “more realistic” cosmological simulation of galaxy formation with additional observable predictions
Means:
Use Gadget +SubgridISM
Status:
Testing Implementation + Physical consistency
Why is this interesting?
• Stars form in molecular clouds in the MW/other nearby galaxies (Blitz 1993, Fukui &Kawamura 2010)
• SFR seems to be correlated stronger with the H2 surface density than the HI surface density (Wong & Blitz 2002)
• Jury is still out on whether stars form from H2 or both form under similar conditions
•Many CO/H2 observations to match
SGISM | Model•H2 formation on dust grains
•H2 destruction by UV radiation (self-shielding + dust shielding)
•H2 destruction by collisions in WNM phase
• time-dependent algorithm
• star formation recipe based on H2 fraction + stellar feedback
•Metal + H2 cooling
Pelupessy et al. 2006, 2009
SGISM | Parameters
•H2 formation uncertainties fudge factor
• unknown density profile in molecular clouds
•Ortho-to-Para ratio of hydrogen
SGISM | Parameters
•H2 formation uncertainties fudge factor
• unknown density profile in molecular clouds
•Ortho-to-Para ratio of hydrogen
Do not seem to introduce the biggest uncertainties!
SGISM | Model
Pelupessy et al. 2006, 2009
n, T, Z, ne, dt
SGISM | Temp. Dependence
Pelupessy et al. 2006, 2009
T > T4 = 104K:No molecular hydrogen can exist above thistemperature (Cazaux & Tielens 2004).
T4 ≥ T > Tdes = 3× 103K:H2 destruction through collisions.
Tdes ≥ T > Tform = 103KH2 destruction through external radiation field.
Tform ≥ T :H2 formation in equilibrium with destructionthrough external radiation field.
Subgrid ISM | H2 Fraction
Figure 3: The equilibrium molecular fraction fm in dependence of the gas num-ber density n and the gas temperature T for di!erent parameter sets. Theseplots show the contours corresponding to fm = 0.1, 0.3, 0.6, 0.9, respectively.The plots are created for a formation rate parameter µ = 3.5 and values forthe cloud power-law index !, the metallicity Z the radiation field G0 in unitsof the Draine field and the velocity dispersion "/km/s as denoted in each plot.These plots are analogous to Figure 1 in [8].
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Cloud Model
Radiation field
Vel. Disp.
Metallicity
fH2 =2nH2
n
Subgrid ISM | H2 Fraction
Figure 3: The equilibrium molecular fraction fm in dependence of the gas num-ber density n and the gas temperature T for di!erent parameter sets. Theseplots show the contours corresponding to fm = 0.1, 0.3, 0.6, 0.9, respectively.The plots are created for a formation rate parameter µ = 3.5 and values forthe cloud power-law index !, the metallicity Z the radiation field G0 in unitsof the Draine field and the velocity dispersion "/km/s as denoted in each plot.These plots are analogous to Figure 1 in [8].
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Cloud Model
Radiation field
Vel. Disp.
MetallicityMetallicity
fH2 =2nH2
n
SGISM | Metal Cooling
from C, N, O, Ne, Si, Fe
Raga et al. 1997, Silva & Viegas 2001
SGISM | H2 Cooling
LeBourlot et al. (1999)
n = 104cm−3
n = 100cm−3
n = 108cm−3
O/P = 1
fH2 = 0.9
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM in Gadget | Status
•H2 formation + destruction
• Primordial Cooling + Heating
•Metal Cooling
•H2 Cooling
•H2 based star formation
• Stellar Feedback
• ...
Pelupessy et al. (2006,2009), Katz et al. (1996), Le Bourlot et al. (1999), Silva & Viegas (2001)
SGISM | Tests
• collapse of a self-gravitating rotating gas sphere
• initially softened NFW profile (e.g. Sijacki et al. 2012)
• N = 104, M = 1012M⊙, Λ = 0.05
SGISM | Tests
SGISM | Tests
Outlook | Tests
•Investigating the effect of resolved/unresolved metallicity
•non-cosmological runs (mergers)
Outlook | Physics
• Low Z, H2 Formation (For Cosmologial Simulations)
•CO Formation/Destruction (Pelupessy et al. 2009)
•Non-Standard SPH (SPHS/ Hopkins 2012)
•Radiative Transfer
•Metal Diffusion?
SGISM | Summary
•H2 formation/destruction + cooling modules work as stand alone versions
• Implementation in Gadget still needs to be smoothed out
•More tests needed!
•More physics needed for consistent treatment!