galactic dynamics in the era of gaia · galactic dynamics in the era of gaia amina helmi o) how did...
TRANSCRIPT
![Page 1: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/1.jpg)
Galactic dynamics in the era of Gaia
Amina Helmi
Credits:)ESA
/Gaia0CC
)BY0SA
)3.0)IG
O)
![Page 2: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/2.jpg)
How did the Galaxy come to be like this?
• We can observe individual stars and measure their properties • Decipher sequence of events of formation of a typical galaxy
• Distributed in various Galactic components, each with specific characteristics • e.g. halo stars are as nearly as old as the Universe
• The Milky Way is a Rosetta stone
![Page 3: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/3.jpg)
t = 1 Gyr t = 2 Gyr
t = 3 Gyr t = 4.5 Gyr
t = 8 Gyr t = Tnow today
Galactic Archaeology
• Key ingredient of galaxy formation: mergers
• Were mergers important for galaxies like the Milky Way?
• How often and when did they happen? • What were the building blocks?
• Stars are “fossils” – Motions, ages, chemical composition
trace origin – Substructures pinpoint to debris from
accretion events – Probe force field ! mass (gravity)
snapshots:)J.)Gardner)
![Page 4: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/4.jpg)
Testing the cold dark matter paradigm Is this “picture” correct?
• Are galaxies like the Milky Way and its nearest neighbours embedded in dark matter halos like those predicted by the cosmological model?
Cre
dit:
V. S
prin
gel
![Page 5: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/5.jpg)
Testing the cold dark matter paradigm Is this “picture” correct?
• Are galaxies like the Milky Way and its nearest neighbours embedded in dark matter halos like those predicted by the cosmological model?
![Page 6: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/6.jpg)
Testing the cold dark matter paradigm Is this “picture” correct?
• Are galaxies like the Milky Way and its nearest neighbours embedded in dark matter halos like those predicted by the cosmological model?
• How much dark matter is there? – how is it distributed? – what is the dark matter?
• Is Gravity correct?
Cre
dit:
V. S
prin
gel
![Page 7: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/7.jpg)
The Gaia revolution: starting now!
(1 km/s proper motions)
Gaia will measure positions and motions of stars for 109 stars (10,000x larger than predecessor); over a volume 100,000 larger; up to 1,000x more precisely ! transformational
![Page 8: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/8.jpg)
up to 21 million objects/deg2
By Jan. 2015, 16 billion photom/astrom transits, 1.6 billion spectroscopic
Courtesy of Anthony Brown & Gaia/DPAC
• Simultaneous astrometry, photometry, spectroscopy • Complete to G = 20.7 (V = 20-22), G = 16 for spectroscopy
• Whole sky already observed! • First data release in mid-2016 (positions + G magnitude) • DR2 in Jan 2017: full phase-space
![Page 9: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/9.jpg)
Courtesy)A.)Brown))
![Page 10: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/10.jpg)
Phot
omet
ry
RR
Lyr
ae in
the
LM
C
Spectroscopy: RVS
Spectro-photometry astrophysical parameters
“Image of the week” http://www.cosmos.esa.int/web/gaia/
![Page 11: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/11.jpg)
)Gaia)astrometric)data)reduc9on)
Disentangling)parallax)and)proper)mo9on)needs)more)than)1)yr)of)data)
Courtesy)U.)Lam
mers,)T.)PrusA,)A
.)Brown)an
d)DPAC)
![Page 12: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/12.jpg)
)Gaia)astrometric)data)reduc9on)
Disentangling)parallax)and)proper)mo9on)needs)more)than)1)yr)of)data)
Gaia/AGIS)team)wanted)to)experiment)with)full)5Dparameter)solu9ons)as)soon)as)possible)
Courtesy)U.)Lam
mers,)T.)PrusA,)A
.)Brown)an
d)DPAC)
![Page 13: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/13.jpg)
)Gaia)astrometric)data)reduc9on)
Disentangling)parallax)and)proper)mo9on)needs)more)than)1)yr)of)data)
Gaia/AGIS)team)wanted)to)experiment)with)full)5Dparameter)solu9ons)as)soon)as)possible)
Combine)with)posi9ons)of)stars)in)Tycho)catalog:)pm)and)par)for)2.5)million)stars)
Courtesy)U.)Lam
mers,)T.)PrusA,)A
.)Brown)an
d)DPAC)
![Page 14: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/14.jpg)
(Very))preliminary)results)on)TGAS)parallaxes)
Courtesy)U.)Lam
ers,)T.)PrusA,)A
.)Brown)an
d)DPAC)
![Page 15: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/15.jpg)
What)do)we)know)now)about)the)Galaxy?)
What)are)some)of)the)open)ques9ons?)
Assembly)history)of)the)Milky)Way)The)Galac9c)dark)halo))
![Page 16: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/16.jpg)
Belokurov)et)al.)2006)+)
Outer)halo:)• Clear)evidence)of)substructure)• Limited)to)highDsurface)brightness)features)(progenitors/9me)of)events))• Qualita9vely)consistent)with)expecta9ons)from)LCDM)(Helmi)et)al.)2011;)Deason)et)al.)2014))
North)Galac9c)Cap)
Galac9c)An9centre)Slater)et)al.)2014+)
The)accre9on)history)unveiled)so)far:))The)Galac9c)halo)from)SDSS/PanStarrs)
![Page 17: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/17.jpg)
Kinema9cs)for)large)numbers)of)halo)stars:)crucial)
![Page 18: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/18.jpg)
angular momentum en
ergy
conserved)quan99es)100s of streams predicted near the Sun and possibly hiding…
How to find these? Gaia! • Clustering in conserved quantities • Follow-up: SFH and chemical evolution of building blocks " FLAMES, 4MOST & WEAVE
Kinema9cs)for)large)numbers)of)halo)stars:)crucial)
Helmi)&
)de)Zeeu
w)200
0)
![Page 19: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/19.jpg)
Streams, orbits and gravitational potentials As satellite galaxy disrupts, stars delineate nearly an orbit
Present-day spatial distribution (density, shape, total mass): consistent with �CDM? Granularity (critical test of �CDM) e.g. Johnston et al. 2002; Yoon et al. 2011; Carlberg 2012/2013 Time-evolution e.g. Peñarrubia et al. 2005; Gomez & Helmi 2010, Buist & Helmi (2015)
![Page 20: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/20.jpg)
The)dark)halo)• Total)mass:))7)x)1011)–)2)x)1012)Msun))(factor)3)uncertainty!))• Rota9on)curve,)density)profile)…)poorly)characterized)
• Shape)constraints:))– CloseDin:)Pal)5)streams)not)too)flajened)towards)disk)(q)~)0.95,)Kupper)et)al.)2015))
– At)large)distance:)possibly)triaxial)at)large)distances)but)based)on)just)1)stream:)Sagijarius;)very)debated)
Kupper)et)al.)(2015))
![Page 21: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/21.jpg)
The Milky Way's dark halo shape and Sgr stream
• If halo is spherical, motion is in a plane – Deviations, if any, tell us shape
• in CDM halos are triaxial at large radii
• PUZZLES from models of Sgr stream in axisymmetric potentials – Precession signal (non-spherical halo):
clearly favour OBLATE (Johnston et al. 2005)
– Radial velocities: clearly favour PROLATE (Helmi 2004)
Law
et
al. 2
005
![Page 22: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/22.jpg)
Solution: A triaxial halo? • Model by Law & Majewski (2010)
# Positions on the sky (hence precession) and radial velocities
• However, it is odd…nearly oblate shape – Symmetry plane: yz, i.e. perpendicular to the disk " not a stable configuration/nor intuitive physically
• Constraints on inner shape weak: can accommodate an oblate flattened inner halo (Vera-Ciro & Helmi 2013)
– Why long axis along y? • LMC provides additional significant torque " effective potential is sum of contribution of triaxial
MW halo + LMC " indistinguishable so far
Vera-Ciro &
Helm
i, 2013
![Page 23: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/23.jpg)
Is this “picture” correct?
Granularity: Hundreds of thousands dark clumps if dark matter particle is cold
Springel)et)al.)2008)Koposov)et)al)2009)
![Page 24: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/24.jpg)
Summary / Next steps • Milky Way: A revolution can be expected with Gaia satellite mission
– Many streams (soon to be) discovered – Modeling of the dark halo shape from Sgr streams accommodates inner oblate and outer triaxial – Next: halo’s density profile, mass and granularity (missing satellites) as well as time evolution – History of formation of the Milky Way
• Milky Way unique probes of cosmology – Provided some of the most stringent tests and flaws/problems of the CDM model – There is much more to come!
![Page 25: Galactic dynamics in the era of Gaia · Galactic dynamics in the era of Gaia Amina Helmi O) How did the Galaxy come to be like this? • We can observe individual stars and measure](https://reader034.vdocuments.us/reader034/viewer/2022042209/5ead68de8af11c63ff5302b2/html5/thumbnails/25.jpg)
ESADESO)Galaxy)WG )))))ESADESO)mee9ng,)ESTEC,)10)October)ESADESO)2008) 25)
Thank)you)for)your)ajen9on)