advertisement

jsimon irvine

50 %
50 %
advertisement
Information about jsimon irvine
Science-Technology

Published on August 29, 2007

Author: CoolDude26

Source: authorstream.com

advertisement

The Observational Distribution of Dark Matter Density Profiles:  The Observational Distribution of Dark Matter Density Profiles Josh Simon Caltech Collaborators: Alberto Bolatto (Berkeley) Jeremy Bailin (Swinburne) Adam Leroy (MPIA)and#x18;and#x13; Leo Blitz (Berkeley) Outline:  Outline The central density problem Observational systematics or serious problem for CDM? New survey of galaxy velocity fields Density profile results Comparison with CDM What do the differences between simulations and observations mean? Teaser: dark matter in dwarf spheroidals The Central Density Problem:  The Central Density Problem Parameterize density profile as r(r) µ r -a Observations show a ~ 0 (constant-density core) Simulations predict 1  a  1.5 (central cusp) cusp core Are Systematics a Problem?:  Are Systematics a Problem? Beam smearing Slit errors Noncircular motions Are Systematics a Problem?:  Are Systematics a Problem? Beam smearing Observing nearby galaxies (d andlt; 15 Mpc) yields spatial resolution andlt; 300 pc Systematic Uncertainties:  Systematic Uncertainties Beam smearing Slit errors Slit position and angle may be off, slit width and seeing smooth the data, etc. Potentially cause large biases in measured value of  (Swaters et al. 2003; de Blok et al. 2003; Spekkens et al. 2005) Problems avoided with 2D velocity fields Systematic Uncertainties:  Systematic Uncertainties Beam smearing Slit errors Noncircular motions Can’t be detected with long slit data Can be detected and modeled with 2D data (Swaters et al. 2003; Simon et al. 2003, 2005; Gentile et al. 2007) Survey Design:  Survey Design Observations and target selection Survey Design:  Survey Design Analysis Target Galaxies:  Target Galaxies Sample of 8 galaxies with 3 Mpc andlt; D andlt; 16 Mpc, 46° andlt; i andlt; 76°, and -20and#x18;and#x13; andlt; MB andlt; -17 Velocity Fields:  Velocity Fields Sample of 8 galaxies with 3 Mpc andlt; D andlt; 16 Mpc, 46° andlt; i andlt; 76°, and -20and#x18;and#x13; andlt; MB andlt; -17 Tilted Ring Modeling:  Tilted Ring Modeling Tilted ring model In each ring, fit V(f): Vobs(f) = vsys + vrot cos f + vrad sin f Tilted-Ring Modeling Results:  Tilted-Ring Modeling Results Radial velocity Rotation velocity NGC 2976 (core) NGC 5963 (cusp) Is There a Universal Density Profile?:  NGC 2976 Eight galaxies: a 0.01 NGC 2552 0. NGC 4605 0. NGC 6689 0. NGC 5949 0. NGC 6207  NGC 5963  NGC 6503  Is There a Universal Density Profile? Is There a Universal Density Profile?:  NGC 2976 Eight galaxies: a 0.01 NGC 2552 0. NGC 4605 0. NGC 6689 0. NGC 5949 0. NGC 6207  NGC 5963  NGC 6503  Is There a Universal Density Profile? Is There a Universal Density Profile?:  No evidence for a universal density profile large scatter compared to simulations:  = 0.4 instead of 0.14 mean slope shallower than simulations:  = 0.8 instead of 1.16 Simon et al. 2005; Diemand et al. 2004 Is There a Universal Density Profile? Density Profile Distribution:  Density Profile Distribution Simon et al. 2005, this work Diemand et al. 2004 a = 1.16 ± 0.14 a = 0.8 ± 0.4 What do these differences mean?:  What do these differences mean? We don’t understand the observations? We don’t understand how to compare the observations and the simulations? We don’t understand galaxy formation? We don’t understand dark matter? Comparing Observations and Simulations:  Comparing Observations and Simulations dark matter only often assume a spherical halo measure densities exactly stars + gas + dark matter baryonic disk in a triaxial halo derive densities from disk velocity field CDM simulations Observations “Observing” Simulated Galaxies:  'Observing' Simulated Galaxies Start with a triaxial NFW halo Add a disk Iteratively and self-consistently calculate the net potential felt by the disk (Bailin, Simon, et al., in prep) Then, randomly choose a line of sight and build a mock data cube that matches WIYN H observations and analyze as with the real data Effect of Triaxiality on the Disk:  Effect of Triaxiality on the Disk Solid lines: magnitude of the initial elliptical perturbation to the potential from halo triaxiality Dashed lines: magnitude of the net perturbation to the potential after including the response of the disk Bailin, Simon, et al. (in prep) Hayashi andamp; Navarro 2006 Tilted-ring models of simulated galaxies:  Tilted-ring models of simulated galaxies Radial velocity Rotation velocity Triaxial halo (=0°) Spherical halo Halos with same density profile and orientation, but different axis ratios:  = 1.16 power law Tilted-ring models of simulated galaxies:  Tilted-ring models of simulated galaxies Triaxial halo (=45°) Spherical halo Halos with same density profile and orientation, but different axis ratios:  = 1.16 power law Radial velocity Rotation velocity Tilted-ring models of simulated galaxies:  Tilted-ring models of simulated galaxies Triaxial halo (=90°) Spherical halo Halos with same density profile and orientation, but different axis ratios: Pseudo-isothermal Radial velocity Rotation velocity Tilted-ring models of simulated galaxies:  Tilted-ring models of simulated galaxies Triaxial halo (=135°) Spherical halo Halos with same density profile and orientation, but different axis ratios: Pseudo-isothermal Radial velocity Rotation velocity Cores or Triaxial Halos?:  Cores or Triaxial Halos? Why do the galaxies with the shallowest density profiles have the largest noncircular motions? NGC 2976 a = 0.01 UGC 12632 a = 0.26 NGC 2552 a = 0.47 Remember: long slit studies could not have seen this! Slide27:  Dark matter in ultrafaint dSphs:  Dark matter in ultrafaint dSphs Velocity dispersions of 7 newly discovered MW dSphs In collaboration with Marla Geha (HIA) Dark matter in ultrafaint dSphs:  Dark matter in ultrafaint dSphs 'Mateo' plot, data from Gilmore et al. (2007) and Simon andamp; Geha (in prep) Mhalo = 5 x 106 M Mhalo = 2 x 107 M Conclusions: Is There a Central Density Problem?:  Conclusions: Is There a Central Density Problem? There are cuspy galaxies NGC 5963 (Simon et al. 2005) NGC 5585 and NGC 2403 (Dutton et al. 2005) NGC 4395 (Kuzio de Naray et al. 2006) On average, observed density profiles are shallower than predicted by simulations, and have more scatter from galaxy to galaxy a = 0.8 ± 0.4 Observational systematics no longer a problem, but more realistic comparisons between observations and simulations are needed Triaxiality can potentially explain the remaining differences

Add a comment

Related presentations

Related pages

Simon & Simon, PC - A Full Service Personal Injury Law Firm

Simon & Simon, PC is a full-service personal injury law firm assisting injured victims and their families who have suffered due to the negligence of others.
Read more

Simon Davis Inc.

Since 1963 Simon Davis Brokerage Services, Inc. has supported hundreds of top financial professionals by providing them with leading ...
Read more

Jim S.'s Reviews | Santa Ana - Yelp

Irvine, CA 92614 5/18/2012 ... http://jsimon.yelp.com About. About Yelp; Order Food on Eat24; Careers; Press; Investor Relations; Content Guidelines; Terms ...
Read more

SMEC Enforces Best Practices with Epicor® Solutions

949/585-4235 jsimon@epicor.com lpreuss@epicor.com ... Epicor’s worldwide headquarters are located in Irvine, California with offices and affiliates
Read more

Josh's CV - users.obs.carnegiescience.edu

JOSH SIMON. Observatories of the Carnegie Institution of Washington 813 Santa Barbara St. Pasadena, CA 91101 Phone: (626) 304-0256 CURRENT POSITION
Read more

Denver Commercial Real Estate Brokers | HFF

Our Denver office provides commercial real estate services for all property types throughout the Rocky Mountain region.
Read more

LA to San Diego Drive Advise | Tesla Motors

LA to San Diego Drive Advise. LA to San Diego Drive Advise . Submitted by jsimon on February 22, 2015. So I just ordered my P85D. Obviously beyond excited.
Read more

Constraining the Nature of Dark Matter With Next ...

Constraining the Nature of Dark Matter With Next Generation Telescopes Josh Simon Caltech Collaborators: Louie Strigari (Irvine) James Bullock (Irvine)
Read more

TEACHING MULTI-OBJECTIVE MULTI-STAKEHOLDER DECISION ...

TEACHING MULTI-OBJECTIVE MULTI-STAKEHOLDER DECISION MODELING WITH CASES L. Robin Keller*, Jay Simon** * University of California, Irvine, USA
Read more

St. Louis Attorneys and Counselors at Law | Injury Firm in MO

The St. Louis personal injury attorneys at The Simon Law Firm, P.C. recovered $760 million for clients. Let them fight for you! Call for a free case review.
Read more