de Recherche Astronomique de Lyon, France 2 Instituto de Astronomia, Ensenada, UNAM, Mexico 2006 july 10th
Eskridge et al 2000 AJ 119, 536
Jogee et al. 2004 ApJ 615, L105
2006/07/10
Sheth et al. 2003 ApJ 592, L13
2
Why studying barred galaxies?
Bars are the main drivers of evolution of disc galaxies between major merger events A stellar bar is able to:
Bring gas from the disc to the central region Enhance star formation Reshape the stellar disc Homogenize distribution of elements
Strong constraints on dark matter distribution
Slowdown rate of bar rotation is linked to halo concentration (dynamical friction ⇒ angular momentum bar → halo exchanges) z=0 bars slow of fast rotators ?
2006/07/10
3
Observation/simulation duality Observation of stellar bars Length
N-body simulations (Theory) Corotation radius
Relationship
Axis ratio (ellipticity)
Strength
1 ≤RCR/Rbar≤1.7 (obs) or 2.6 (sim) ~ correlation (trend)
Luminosity
Mass
M/L
Line-of-sight kinematics
3D kinematics
Dark matter
…
…
…
2006/07/10
4
Comparing simulations with observations Athanassoula & Misiriotis 2002 MNRAS 330, 35 Bar lengths
λ=1.4 (Kennicutt 1990) SFE = 0.1 creation of new stellar particles (remnants) SNII mechanical fraction of energy = 0.1
Maeder’s yields (1992) → metallicities cooling with solar abundances (Bohringer & Hensler 1989)
2006/07/10
6
Simulations parameters & calibration
5-6 105 stellar particles (initial pop.) → ~ 1.2 106 at the end 1-5 104 SPH particles Mg / M¹ ~ 0.1 – 0.3 initial disc scalelengths : 3.5 to 5.5 kpc initial disc scaleheights: 0.5 to 1 kpc Photometric calibration
SSP from Bruzual & Charlot (2000 release) Salpeter IMF 0.1 to 100 M~ Z of initial stellar pop = 0.004 initial age (4.4 to 10.4 Gyr) leads to z=0 at the end of the simulation
2006/07/10
7
10 kpc
16 kpc
Star formation rates Bar formation
2006/07/10
9
Measuring bar lengths… Ellipse-fitting methods: ---- Mass ---- B ---- K
max: used by e.g. Jogee et al. 2004 plateau: Michel-Dansac & Wozniak 2006 drop: used by e.g. Sheth et al. 2003
max
plateau
2006/07/10
Sheth et al. 2003 ApJ 592, L13
drop
10
…and ellipticities.
max ellipticity
Mass density
2006/07/10
B
B + absorption
K
K + absorption
---- Mass ---- B ---- K
11
Bar strength and ellipticity evolution
max ellipticity
---- Mass ---- B ---- K Combes & Sanders 1981 :
Qb
2006/07/10
12
Bar strength – ellipticity correlation Laurikainen et al. 2002 MNRAS 331, 880 2MASS galaxies
From MD&W 2006 simulations • Mass •B •K
2006/07/10
13
Resonances in barred galaxies
corotation radius (Rcr)
Ωb: pattern speed Ω: circular orbit frequency κ: radial epicyclic frequency
For each snapshot: • froze the potential • compute of orbits for several dynamical time ⇒ orbital frequencies (Ω,κ) κ ⇒ families of resonant particles ⇒ resonances location
Ωb 2006/07/10
Ω 15
Bar length and resonances evolution corotation ↔ ellipticity drop
---- Mass ---- B ---- K
UHR ↔ PA plateau
Radius (kpc)
ILR ≠ max ellipticity
Time (Gyr) 2006/07/10
16
Fast or slow bars ? Aguerri et al. 2003 MNRAS 338, 465 Rautiainen et al. 2005 ApJ 631, L129 PA plateau
2006/07/10
ellipticity drop
Rcr = 1.4 Rbar
Rcr = Rbar
17
Conclusions
Comparison observation/simulation :
Bar strength / ellipticity
need to calibrate simulations use of chemodynamical simulations
Improved Polar PM + SPH + SF code. â More accurate self-forces (sub-gridding). â Spatial resolution increased (15 pc in the central region). â CFL condition ...
photoelectric heating from grains and PAHs (Wolfire et al., 1995, ApJ, 443, 152) ... Evolution of the total stellar mass formed (left) and of the percentage of cold gas ... Temperature distribution of the variable phase for the whole galaxy (blue) ..
Mar 19, 2010 - 2007 episodic SF over a long period. Maoz et al. 2001 : continuous SF ... Integral Field Spectrograph. Number of modules. 24. Detectors.
Feb 23, 2005 - distance is to use Hubble's law for the expansion of the universe and to .... This method is in a sense optimal to detect lines of the size of the ...
'Memory' network states, with a small fraction of neurons (specific to each memory state) active at higher rates. .... (capacity of order C = number of synapses per neuron). (Sompolinsky .... More realistic networks (network of spiking neurons) ...
Muscle + reflex. â Basic circuit for motor ... muscle/reflex behaves as nonlinear spring with variable threshold length. ... Incompatible with data on forearm flexion.
including products of theoretical research. .... Power-law cosmological simulations and merger- tree/halo ... computing and applied mathematics for the formation.
coordinate and assist European Data Centres to take up VO standards. â share best ... consolidate operational requirements for VO-enabled tools and systems.
plates, and thus PAH bands may be present. A detection of the 11.3 /m ..... tudes in the V-band) is consistent with the small 11.9/12.9 and. 10.4/11.9 flux ratios ...
In the case of NGC 2992, an upper limit to the extended MIR emission can be set. We provide ..... not the case. An analysis on a larger sample and from images.
Jul 26, 2010 - tion of this problem is expressed in terms of op- ..... designates the pseudo-inverse of op- ..... phase obtained after a switch to α (that is, for ex-.
13 juil. 2019 - If you are interesting in different niche as well as subject, you may surf our wonderful selection of our electronic book collection which is ...
endogenous, even assuming temporal independence of error terms. ... period analyzed, the annual total sample size was about 30 thousand households, which.
Jan 20, 2005 - ... or accident). Traffic jam. (Department of Physics, University of Illinois at Urbana-Champaign) ..... transition from randomness or chaos to order ...
behavioural responses/repertoire of mice is, of course, very different from the .... basis of anxiety, for screening anxiety-modulating drugs or mouse genotypes [4 ...
Improving models of forest nutrient export with equations that predict the nutrient .... production of each tree compartment with its mean nutrient concentration. ...... crowns with application to modelling the foliage area distribution in the crown.
