The Magellanic Stream: the ’ram pressure plus collision’ scenario
by François Hammer
With Yanbin Yang, Hector Flores, Mathieu Puech, Sylvain Fouquet
Cleveland, June the 9th Francois Hammer: The Magellanic Stream The HI Magellanic Stream: 230° length, with Leading Arm
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Southern Hemisphere in HI from GASS
High velocity clouds (HVCs) Magellanic Stream (MS)
SMALL MAGELLANIC CLOUD (LMC) LARGE MAGELLANIC CLOUD (LMC)
Milky Way (MW)
Leading Arm (LA)
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Explana on of the gigan c Magellanic Stream
Z
Firstly identified as the MS by Mathewson+74 after detections by van SUN Kuilenburg and Wannier & Wrixon72 LARGE MAGELLANIC CLOUD (LMC)
SMALL MAGELLANIC CLOUD (SMC)
30 KPC Cleveland, June the 9th Z - Francois Hammer: The Magellanic Stream Why dal models are not predic ve? • Can’t explain absence of stars
• Can’t explain the filamentary structure nor the 4 Leading Arm structures ) -2
Observations Log(N(HI)cm Besla+2012) Magellanic Longitude (L ) MS • Already lack 9/10 of N(HI)
• Could not explain large ionized 9 Cleveland, June the 9th gas amount (2 10 MO, Fox+14) Explana on of the gigan c Magellanic Stream
Z
Firstly identified as the MS by Mathewson+74 after detections by van SUN Kuilenburg and Wannier & Wrixon72 LARGE MAGELLANIC CLOUD (LMC)
Mathewson (2012): SMALL MAGELLANIC CLOUD (SMC) still no satisfactory explanation since 1974
30 KPC Cleveland, June the 9th Z - Francois Hammer: The Magellanic Stream The filamentary structure of the MS
Cleveland, June the 9th Francois Hammer: The Magellanic Stream • Filamentary structure of the MS • DNA-like appearance Putman+03 and references therein
Cleveland, June the 9th Francois Hammer: The Magellanic Stream 30 Doradus SF region MS with 2 filaments Nidever+08
Cleveland, June the 9th Francois Hammer: The Magellanic Stream LMC
SMC
GASS V1 Kalberla+10 V3 V5 V2 V4
Cleveland, June the 9th Francois Hammer: The Magellanic Stream M31$ IC10$
S0$ (1)$MS,II,III,IV$ LMC$ Leading$Arm$ SMC$
(2)$MS,II,III,IV$(GASS)$ LMC filament GASS WLM$ PHL$2525$
SMC filament
Cleveland, June the 9th Francois Hammer: The Magellanic Stream +1( +1( ΔVmax=27(km(s ΔVmax=17(km(s
ΔV =26(km(s+1( max Vortices?
+1( ΔVmax=46(km(s +1( +1( ΔVmax=36(km(s ΔVmax=30(km(s Rotational vortices in a transonic flow (Mach=1.5) Cleveland, June the 9th Francois Hammer: The Magellanic Stream Similar behaviour than hydrodynamical flows with similar (Re, Strouhal) numbers, including vortices (or hairpin shedding)
+1( +1( ΔVmax=27(km(s ΔVmax=17(km(s
+1( ΔVmax=26(km(s First wake instabilities on a flow, Re=400, Wesfreid et al. 2014
+1( ΔVmax=46(km(s +1( +1( ΔVmax=36(km(s ΔVmax=30(km(s
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Ram pressure exerted by the hot gas (106K) of the Milky Way halo
Evidences for a prominent halo hot gas affecting the Magellanic Stream & Clouds:
- Associated high velocity clouds are disrupted (multi-phases, -4 -3 Karlberla & Haud, 2006) è ρhot~ 10 cm at 50 kpc
- X-ray observations (Gupta et al., 2012, Hodges-Kluck, Miller & Bregman, 2016)
- LMC gas disk has shrunk (Nidever, 2013)
Cleveland, June the 9th Francois Hammer: The Magellanic Stream The unusual properties of the LMC disks RGB+AGB (van der Marel, 2006)
HI (Kim 98) Images scaled
Cleveland, June the 9th Francois Hammer: The Magellanic Stream5 kpc Ram-pressure plus collision scenario Hammer et al. 2015
-4 -3 • Evidence for ρhot~ 10 cm at the MS distance (Kalberla & Haud, 2006) • consistent with the fact that the LMC HI disk has been shrunk
• Gas of the Magellanic Clouds stripped by ram-pressure exerted by the hot gas in the Milky Way halo • Feedback is expelling gas at the LMC outskirts, consistent with observations of 30 Doradus (Nidever+08)
• The Magellanic Stream: Two gigantic transonic filaments -1 • Re = 445 x fµ with fµ ≤1 (viscosity suppression factor, Roediger et al. 2013), implying a moderately turbulent MS
• Mach~ 1.5 (Vsound ~ 200 km/s, V ~ 300 km/s)
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Ram-pressure plus collision scenario Hammer et al. 2015
~ 200 Myr old collision between the Magellanic Clouds
Evidenced by:
the Bridge
same SFH peak of the Clouds
proper motions Putman+2000
Relics in GASS data (anomalous HVCs)
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Modelling
GADGET2 (2 M particles)
11 • Milky Way: total mass, 5 to 8 10 MO 10 hot gas mass, 3 to 9 10 MO
2 Gyr in isolation to equilibrate hot gas halo and cold gas in disk within the dark matter halo
9 • Initial LMC: mass, 1.8-5 10 MO; fgas, 40-60% • Initial SMC: mass ~ 0.7 LMC mass, fgas, 40-70%
Reproduce present-day stellar and gas mass within 20% accuracy Assume present-day locations and proper motions of both Clouds
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Francois Hammer: The Magellanic Stream Francois Hammer: The Magellanic Stream Explana on of the gigan c Magellanic Stream
Francois Hammer: The Magellanic Stream Formation of the Leading Arm (LA)
Former passages of leading and ram-pressure stripped dIrrs (a la Lucio Mayer, 2009; LA firstly reproduced by Yang et al; 2014)
Similar orbits than LMC’s, ALL material being part of the VPOS (Pawlowski14) Cleveland, June the 9th Francois Hammer: The Magellanic Stream Vast Polar Structure surrounding the Milky Way VPOS, Pawlowski+12
Milky Way disk
Courtesy: M. Pawlowski
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Explana on of the gigan c Magellanic System Gas of the Clouds and dSph progenitors stripped by ram- pressure exerted by the hot gas in the Milky Way halo, dSph progenitors follow similar orbits than the LMC (VPOS)
Observation Model
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Ram pressure + collision between Magellanic Clouds: the only model reproducing Magellanic Stream proper es Don Ma hewson: “much, much nearer the truth!”
Magellanic Stream: a corner stone to understand the Local Group content and origin
• Kinema cs of the LMC affected by the recent collision with SMC: rota on consistent with an absence of dark ma er • Leading dwarfs to form the Leading Arm: progenitors of dSphs, which kinema cs can be explained by gas removal (Yang+14), consistent with dal dwarfs • The role of the M31 forma on in the Local Group: Stream p end is poin ng to the M31 system (IC10, Nidever+13) Cleveland, June the 9th Francois Hammer: The Magellanic Stream IN PROGRESS • Implemen ng hydrodynamical solver (GIZMO, Hopkins, 2014) to reproduce KH instabili es (vor ces) incl. SF in the Leading Arm (Case +14) • The only chance to reproduce a gas deposi on up to few 109Mo (ionized gas, Fox+14), i.e., close to the gas content of the Milky Way disk • Also to reproduce the dispersion along the Stream
Cleveland, June the 9th Francois Hammer: The Magellanic Stream M31$ IC10$
S0$ LMC$ Leading$Arm$ SMC$
QSOs from Fox+14
Yellow: LMC material Blue: SMC material
Material from LMC filament systematically metal richer than from SMC filament
Cleveland, June the 9th Francois Hammer: The Magellanic Stream The mass of the LMC
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Collision between the LMC & SMC ~ 200 Myr ago:
• Affect their past orbital motions
• Affect the apparent PM since the LMC has been assumed to be a pure rotating disk by van der Marel+14
• LMC disk shows 50° offset between morphology & kinematics PA (van der Marel+14)
It implies ram pressure model being consistent with LMC proper motions from Kallivayalil+13
Cleveland, June the 9th Francois Hammer: The Magellanic Stream RGB+AGB (van der Marel+06)
HI kinematics(Kim 98)
5 kpc 1◦ = 0.87 kpc for
Cleveland, June the 9th Francois Hammer: The Magellanic StreamD=50 .1 kpc No Dark Ma er in the Magellanic Clouds?
100 100 100 100 Model-385 Model-385 Model-385 Model-385 Model-266 Model-266 Model-266 Model-266 80 80 80 80 Old Stars HI Old Stars HI
60 60 60 60
V (km/s) 40 V (km/s) 40 V (km/s) 40 V (km/s) 40
20 20 20 20
0 0 0 0 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 R (kpc) R (kpc) R (kpc) R (kpc)
model-385 model-266
40 20 40.0 model-385 model-266 15 20
10 0 km/s
5 -20
0 -40 -40.0 9.254..620 x x4.62 9.25 kpc 5 kpc 10 15 20 18.59.26 x 9.2618.5 kpc kpc Cleveland, June the 9th Francois Hammer: The Magellanic Stream Could the LMC be a DM-free dal dwarf?
5-10% Large statistics of TDGs from Kaviraj+12, SDSS merger remnants
With its stellar mass and 25% mass ratio to M31 (1/55), LMC is eligible to be a tidal dwarf from a merger remnant
Cleveland, June the 9th Francois Hammer: The Magellanic Stream LMC proper motions
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Consistency with LMC proper motion (PM, Kallivayalil+13)
Collision between the LMC & SMC 200-300Myr ago:
• Affect their past orbital motions 0.97 P08 K06
0.97 0.4 C09-1 V10 • Affect the apparent PM since the LMC has been assumed to be a pure rotating disk by van der Marel+14 K13 0.2
• LMC disk shows 50° offset between morpho & 0.68 395
385 0.97 266 kinematics PA (van der Marel+14) (mas/yr) N µ 0.0
0.68 Same calculations than van der K97
Marel+14 but for a LMC disk -0.2 0.97 after collision 1.7 1.8 1.9 2.0 2.1 2.2 Cleveland, June the 9th Francois Hammer: The Magellanic Stream −µW (mas/yr) GAIA proper mo ons (van der Marel+16)
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Physics and mass of the hot gas phase in the Milky Way halo
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Feedback is expelling gas at the LMC outskirts, which is then subject to ram pressure to form the MS Consistent with observations of 30 Doradus (Nidever+08)
Kim+98
Feedback prescriptions: 5 times the median Cox+06 value
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Feedback is expelling gas at the LMC outskirts, which is then subject to ram pressure to form the MS Consistent with observations of 30 Doradus (Nidever+08)
Collision is releasing far more gas perhaps sufficiently to 9 report the 2 10 MO of ionized gas reported by Fox+14
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Mass of the hot gas of the MW? Expected to be extremely high (Grcevich & Putman, 2008) if dwarfs were DM-dominated & arriving in a coordinated group 10-3 Grcevich & Putman 2008
) -4
-3 10 Hammer et al. 2015
M M total hot Model 10 M Much lower if caused by
Density (cm (10 Sun) 75 4.8 Yang et al. (2014) TDGs in a tidal tail 10-5 75 3.5 MW122R10x10 66 9.0 MW166R10x10 65 8.1 MW165R10x10 51 4.4 MW108R10x10
50100 200 300 R (kpc)
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Many MW dSphs descendant of tidal dwarfs stripped of their gas?
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Explanation of the whole Magellanic System
Gas of the Clouds and dSph progenitors stripped by ram-pressure exerted by the hot gas in the Milky Way halo dSph progenitors follow same orbits than the LMC (VPOS)
Hammer et al. 2015
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Ram-pressure stripping exerted by halo hot gas to dwarfs Yang et al., 2014 (see also Kroupa, 1997)
Green: gas Red: stars
Yang+14 Prompt disruption & gas removal by hot gas facilitated by absence of DM and large velocity (here TDGs from a tidal tail ejected by an ancient merger at M31) Cleveland, June the 9th Francois Hammer: The Magellanic Stream High values of velocity dispersion: large values of DM/L? Or simply expansion of stars in destroyed dwarfs?
TDG9
5 Mstellar ~ a few 10 MO
Walker+2009, 2012
Cleveland, June the 9th Francois Hammer: The Magellanic Stream Yang et al. 2014: reproduce kinematic and all dSph properties, without dark matter
Cleveland, June the 9th Francois Hammer: The Magellanic Stream