Internal 3D kinematics of dwarf spheroidal galaxies with Gaia + HST - - PowerPoint PPT Presentation

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Internal 3D kinematics of dwarf spheroidal galaxies with Gaia + HST - - PowerPoint PPT Presentation

Feb 06, 2024 293 likes •624 views

Internal 3D kinematics of dwarf spheroidal galaxies with Gaia + HST Davide Massari Dipartimento Fisica e Astronomia - Universita di Bologna Kapteyn Astronomical Institute University of Groningen Main collaborators: A. Helmi, E. Tolstoy,

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“Small galaxies, cosmic questions”, Durham – July 30th, 2019

Davide Massari

Dipartimento Fisica e Astronomia - Universita’ di Bologna Kapteyn Astronomical Institute – University of Groningen Main collaborators: A. Helmi, E. Tolstoy, A. Mucciarelli, L. Sales

Internal 3D kinematics of dwarf spheroidal galaxies with Gaia + HST

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>99%

Dwarf Spheroidals to investigate dark matter

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Dynamics Mass distribution Test DM models

PMs in dSph to investigate dark matter

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Dynamics Mass distribution Test DM models BUT No PMs = mass-β degeneracy

PMs in dSph to investigate dark matter

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Positions + Proper motions for 1.3 billion stars

Golden era of Astrometry: Gaia DR2

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Absolute PMs vs Internal PMs

Absolute proper motions:

  • systemic
  • easier to measure

(large number of members helps)

  • σ(absolute) = σ(single)/sqrt(N*sqrt(N)
  • ingredient to determine orbits

Internal proper motions:

  • how stars move within a stellar system
  • Most difficult to measure
  • σ6PM) 8km/s] < velocity dispersion
  • ingredient to investigate the internal

dynamics of a stellar system “Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Absolute PMs vs Internal PMs

Absolute proper motions:

  • systemic
  • easier to measure

(large number of members helps)

  • σ(absolute) = σ(single)/sqrt(N*sqrt(N)
  • ingredient to determine orbits

Internal proper motions:

  • how stars move within a stellar system
  • Most difficult to measure
  • σ6PM) 8km/s] < velocity dispersion
  • ingredient to investigate the internal

dynamics of a stellar system

σ(PM) < 0.03 mas/sqrt(N*yr at G>19>18

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Absolute PMs vs Internal PMs

Absolute proper motions:

  • systemic
  • easier to measure

(large number of members helps)

  • σ(absolute) = σ(single)/sqrt(N*sqrt(N)
  • ingredient to determine orbits

Internal proper motions:

  • how stars move within a stellar system
  • Most difficult to measure
  • σ6PM) 8km/s] < velocity dispersion
  • ingredient to investigate the internal

dynamics of a stellar system

σ(PM) = sqrt(σ (posI)+σ (posII)) /sqrt(N* Δut

2 2

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Absolute PMs vs Internal PMs

Absolute proper motions:

  • systemic
  • easier to measure

(large number of members helps)

  • σ(absolute) = σ(single)/sqrt(N*sqrt(N)
  • ingredient to determine orbits

Internal proper motions:

  • how stars move within a stellar system
  • Most difficult to measure
  • σ6PM) 8km/s] < velocity dispersion
  • ingredient to investigate the internal

dynamics of a stellar system

σ(PM) = sqrt(σ (posI)+σ (posII)) /sqrt(N* Δut

2 2

G>19aia ??? >>> <<< “Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Proper Motions: HST

PSF knowledge + G>19eometric distortion corrections 0.01 pixels + 0.01 pixels Positional precision = 0.7 mas

Anderson+06

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Proper Motions: Gaia

At the typical magnitude of HB for 100 kpc distant stellar population = Precision similar to HST! G>19AIA-JBD-022 “Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Sculptor dSph PM

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Sculptor dSph PM

Massari et al. 2018

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Sculptor tangential velocity dispersion

No systematic trends wrt colour, magnitude, position Check for systematics magnitude colour X direction Y direction

Massari et al. 2018

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Sculptor tangential velocity dispersion

Sub-sample of 15 best stars

Massari et al. 2018

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Sculptor tangential velocity dispersion

Sub-sample of 15 best stars σR=11.5±4.3 km/sqrt(N*s σT=8.5±3.2 km/sqrt(N*s

Massari et al. 2018

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Strigari, Frank & White 2018 (see also Lazar & Bullock 2019)

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

Sculptor tangential velocity dispersion

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First glimpse of what Gaia will enable in few years “Small galaxies, cosmic questions”, Durham – July 30th, 2019

Strigari, Frank & White 2018 (see also Lazar & Bullock 2019)

Sculptor tangential velocity dispersion

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  • DR1 positions
  • Few stars with precise PMs
  • Location at R>R_h

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

Sculptor tangential velocity dispersion

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Draco Dwarf Spheroidal

6 Massari et al. submitted, arxiv.1904.04037)

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Draco Dwarf Spheroidal

RA-RA60) Dec-Dec60)

  • G>19aia DR2 positions
  • 3 HST pointings taken in 2004
  • 2 pointings within half light radius
  • Distance = 76 kpc (McConnachie 2012)

PM for 149 stars!

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Draco dSph: proper motions

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Draco dSph: proper motions

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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6 hours of observing time with DEIMOS@ Keck telescope

External samples: Armandroff et al.1995 Kleyna et al.2002 Kirby et al.2010 Walker et al.2015

RVs for 81 stars!

Draco dSph: LOS velocities

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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PMs and RVs for 45 members

Draco dSph: membership

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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DRACO Dwarf Spheroidal

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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σR=11.0 km/sqrt(N*s σT=9.9 km/sqrt(N*s σLOS=9.0±1.1 km/sqrt(N*s

Draco dSph: velocity dispersions

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

  • 3.1

+2.3

  • 1.5
  • 2.1
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σR=11.0 km/sqrt(N*s σT=9.9 km/sqrt(N*s σlos=9.0±1.1 km/sqrt(N*s

Draco dSph: dynamical modelling

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

+2.1 +2.3

  • 3.1
  • 1.5
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Draco dSph: dynamical modelling

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Draco dSph: dynamical modelling

Vmax + NFW Plummer Vmax-c (Moline+2017) Mass

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Consistent with DM cusp

Draco dSph: dynamical modelling

Massari et al.2019 submitted

“Small galaxies, cosmic questions”, Durham – July 30th, 2019

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Conclusions

Internal PMs of Sculptor

  • radial anisotropy
  • need to sample the core and improve PMs

β=0.48 Internal PMs of Draco

  • Better PMs than Scl
  • 45 stars with 3D kinematics
  • Support for DM cusp

“Small galaxies, cosmic questions”, Durham – July 30th, 2019