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The Extended HI Environment of M31 Robert Braun (ASTRON)

The Extended HI Environment of M31 Robert Braun (ASTRON). Outline Origins of Environmental HI tidal debris modeling the cosmic web modeling low-mass companions M31 HI Surveys from 50 pc to 200 kpc wide-field WSRT: 60x30 deg wide-field GBT: 7x7 deg WSRT mosaic: 6x3 deg

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The Extended HI Environment of M31 Robert Braun (ASTRON)

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  1. The Extended HI Environment of M31 Robert Braun(ASTRON)

  2. Outline • Origins of Environmental HI • tidal debris • modeling the cosmic web • modeling low-mass companions • M31 HI Surveys from 50 pc to 200 kpc • wide-field WSRT: 60x30 deg • wide-field GBT: 7x7 deg • WSRT mosaic: 6x3 deg • The M31 HI Environment

  3. Origins of Environmental HI • Tidal Debris • Mag. Stream is obvious Galactic example for HI • growing number of (long-lived) stellar stream discoveries • Condensations in Coronal Gas / Cosmic Web / WHIM • evidence from FUSE OVI absorption (Sembach et al. 2003) for Galactic corona, R > 70 kpc, n ~10-4-10-5 cm-3 • kinematic association with HVCs • Gaseous Counterparts of Low-Mass Dark-Matter Halos • “missing” satellites (Blitz et al. 1999, Braun & Burton 1999)

  4. Modeling the Cosmic Web Dave et al. 1999, ApJ 511, 521, 2001, ApJ 552, 473 high res. num. sim. predict cosmic web of filaments between galaxies apparent correspondence with QSO absorbers

  5. Modeling the Cosmic Web WHIM (Ly-limit) DLA Ly-forest Dave et al. 1999, ApJ 511, 521 strong (density-dependent) evolution with cosmic epoch collapse of over-dense regions yields greater proportion of WHIM (z=0)

  6. Modeling the Cosmic Web • ~30% baryons in galaxies ( @ z = 0 ) • association with QSO absorbers with NHI = 1018 – 1022 cm-2 • ~30% baryons in warm-hot inter-galactic medium (WHIM) • condensed, shock-heated phase: T ~ 105 – 107 K • association with QSO absorbers with NHI = 1014 – 1018 cm-2 • ties in with evidence from FUSE OVI absorption (Sembach et al. 2003) for Galactic corona, R > 70 kpc, n ~10-4-10-5 cm-3 • ~30% baryons in diffuse inter-galactic medium • diffuse, photo-ionized phase: T ~ 104 K • association with QSO absorbers with NHI = 1012 – 1014 cm-2 • decreasing (micro- not macro-) neutral fraction with NHI • ~1% at NHI = 1017 cm-2, < 0.1% at NHI = 1013 cm-2

  7. Hierarchical Galaxy Formation and the “Missing Low Mass Companions” Klypin et al. 1999, ApJ 522, 82 Moore et al. 1999, ApJ 524, L19 high resolution numerical simulations predict an order of magnitudemore low mass satellites than observed with vc < 30 km/s:n(M) ~ M-2

  8. “Missing Low Mass Companions” Mini-halo Modeling evolutionary and mass sequence Kepner et al.1999, AJ 117, 2063 Kepner et al. 1997, ApJ 487, 61 • calculations in isolated, inter-galactic environment as function of z • early ionization and baryon evaporation • recent recombination/condensation, HI phase is likely dominant • little chance of internal star formation

  9. “Missing Low Mass Companions” Mini-halo Modeling Sternberg, McKee & Wolfire2002, ApJS143, 419 HI content strongly dependant on local IGM pressure: low pressure (1 cm-3 K) => low neutral fraction (<MHI> ~103 MSun) high pressure (30 cm-3 K) => higher neutral fraction (<MHI> ~105 MSun) expected numbers depend on host mass and search volume: N(>Vmax,<d) = 1.06x103 (Mvir/1012 MSun) (Vmax/8 km/s)-2.75 (d/1 Mpc) predicted population has steep power law in Vmax and therefore MHI!! low Mvir galaxies will NOT have detectable populations for two reasons: (1) IGM pressure and (2) small potential

  10. WSRT Wide-field HI Survey • Braun, Thilker & Walterbos 2003, A&A, 406, 829 and 2004, 417, 421 • Auto-corr. drift-scan survey of 1800 deg2 centered on M31 • ~380 hours observing Aug. 2002 – Oct. 2002 • 48 arcmin x 17 km/s res. over 60 x 30 deg., -1000 < V < 6500 km/s • s = 17 mJy/Beam (at DV = 17 km/s), cf. HIPASS s=14 mJy/Beam • D NHI = 4 x 1016 cm-2 for emission filling the beam (10 kpc at 700 kpc) • (cf. HIPASS D NHI ~ 4 x 1017 cm-2 in 15 arcmin beam) • Galactic CHVCs • Magellanic Stream and Wright’s HVC complex • circum-galactic HI clouds and streams of M31 and M33 • M31/M33 filament near systemic velocity

  11. WSRT Wide-field HI Survey Dirty Channel Maps

  12. WSRT Wide-field HI Survey Cleaned Channel maps

  13. WSRT Wide-field HI Survey Braun & Thilker 2004, A&A, 417, 421 Integrated negative velocity HI, log(NHI) = 17, 17.5, 18,... • > 100 newly detected compact features • Mag. Stream apo-galacticon tail, Wright’s Cloud • faint, compact pop. centered on M31 systemic velocity • M31/M33 filament near systemic velocity, NHI ~ 4x1017cm-2 (peak)

  14. WSRT Wide-field HI Survey Braun & Thilker 2004, A&A, 417, 421 Velocity of peak HI in LGSR frame • > 100 newly detected compact features • Mag. Stream apo-galacticon tail, Wright’s Cloud • faint, compact pop. centered on M31 systemic velocity • M31/M33 filament near systemic velocity, NHI ~ 4x1017cm-2 (peak)

  15. The M31 – M33 filament • connects VSYS of M31 and M33 (170 kpc projected) • continues in anti-M33 direction • filamentary structure within 30 kpc (GBT data) • connects to ongoing fueling of both M31 and M33 (from GBT imaging) WSRT Wide-field HI Survey Braun & Thilker 2004, A&A, 417, 421 Dirty Channel Map Dirty Beam

  16. The M31 – M33 filament • connects VSYS of M31 and M33 (170 kpc projected) • continues in anti-M33 direction • filamentary structure within 30 kpc (GBT data) • connects to ongoing fueling of both M31 and M33 (from GBT imaging) WSRT Wide-field HI Survey Braun & Thilker 2004, A&A, 417, 421 Cleaned Channel Map Dirty Beam

  17. Green Bank Telescopewide-field HI imaging of M31 • Thilker, Braun, Lockman, Corbelli, Walterbos & Murphy 2004, ApJ 601, L39 • 6 OTF passes of 7 x 7 deg. on M31 • (6 of 5 x 5 deg. on M33, & cross-cuts) • ~70 hours observing July - Sept. 2002 • 2kpc x 1 km/s res. over 95 x 95 kpc • s = 6.6 mJy/Beam (at DV = 18 km/s) • D NHI = 1.5 x 1017 cm-2 at 3 kpc resolution • extended rotation curve/warping • outer HI edge, UV rad. field • HI clouds and streams!!!

  18. GBTwide-field HI imaging of M31 DV = 36 km/s

  19. GBTwide-field HI imaging of M31 DV = 72 km/s

  20. GBTwide-field HI imaging of M31 • Thilker et al. 2004, ApJL, 601, L39 • Detection of three distinct HVC populations • tidal streams: partial coincidence with the giant M31 stellar stream of Ibata et al. 2001, Ferguson et al. 2002, McConnachie et al. 2003, some apparent interactions with M31 disk (eg. NGC 205 stream) • diffuse filaments and halo centered on M31 systemic velocity, possible interface to the cosmic web • concentration of faint, compact HVCs centered on M31 systemic velocity which follow kinematic pattern of outer disk rotation • confirmation (with very clean GBT beam) of faint WSRT auto-corr. detections

  21. WSRT HI mosiacof M31 • Braun, Corbelli, Thilker & Walterbos2002 & 2004, in prep • 163 pointings on 15 arcmin Nyquist-sampled grid • ~350 hours observing Aug. 2001 – Jan. 2002 • 50 pc x 2 km/s res. over the 80 kpc disk • s = 1.4 mJy/Beam (at DV = 2 km/s) • DNHI = 1.0, 3.5, 11 and 24 x 1018cm-2 • @ 120, 60, 30 and 20” (DV=20 km/s) • extended rotation curve / warping • outer HI edge / UV radiation field • CNM / WNM in disk • circum-galactic HI clouds and streams

  22. WSRT HI mosiacof M31 • 50 pc x 2 km/s res. over the 80 kpc disk • most detailed ISM cube yet made Braun et al. 2003, in prep

  23. High resolution imaging of M31 CHVC Cores Braun & Thilker 2004, in prep. • From WSRT Mosaic • current spatial coverage includes ~10 examples of near-in CHVCs (< 40 kpc) • multi-phase CNM/WNM structure • peak NHI ~ 1019 -1020 cm-2 • complex internal kinematics

  24. High resolution imaging of M31 CHVC Cores Braun & Thilker 2004, in prep.

  25. High resolution imaging of M31 CHVC Cores Braun & Thilker 2004, in prep.

  26. High resolution imaging of M31 CHVC Cores Braun & Thilker 2004, in prep.

  27. High resolution imaging of M31 CHVC Cores Braun & Thilker 2004, in prep.

  28. High resolution imaging of M31 CHVC Cores Braun & Thilker 2004, in prep.

  29. High resolution imaging of M31 CHVC Cores Westmeier, Braun & Thilker 2004, in prep. • New Pointed Observations • (Dec. 2003) • deep pointed obs. of 10 sub-structures (9 around M31, plus 1 around M33) • compact cores detected in all fields except M31/M33 filament fields

  30. High resolution imaging of M31 CHVC Cores Westmeier, Braun & Thilker 2004, in prep. • complex sub-structure adjacent to “giant stellar stream” • several “intersecting” filaments with smoothly varying velocity • bright isolated clumps, MHI ~ 106 MSun , internal DV ~ 30 km/s • kinematic analysis now underway

  31. The M31 HVC Populations M33 Thilker et al. 2004, ApJL, 601, L39 Braun & Thilker 2004, A&A, 417, 421 wide-field WSRT data wide-field GBT data • extensive tidal stream, halo and discrete HVC populations • combined low NHI distribution has 25 kpc projected exp. scale-length • the discrete population of M31 is less extensive than predicted by the Galaxy model of De Heij, Braun and Burton (2002): s = 150-200 kpc

  32. “Missing Low Mass Companions” The M31 discrete HVC Population (within 40 kpc radius) Braun & Thilker 2003, in prep. • mass distribution: • MHI = 105 – 107 MSun • linewidth-mass roughly consistent with: • MDM ~ 100 MHI • expect N ~ 20 within 40 kpc radius of M31 and detect 22 • Here are the missing low mass companions !! wide-field GBT data

  33. Imaging the low-z Cosmic Web The M31 – M33 filament • connects VSYS of M31 and M33 (170 kpc projected) • continues in anti-M33 direction • connects to ongoing fueling of both M31 and M33 (from GBT imaging) • relative distance and radial velocity imply M33 is likely approaching M31: makes tidal origin unlikely Braun & Thilker 2004, A&A, 417, 421 wide-field WSRT data

  34. Imaging the low-z Cosmic Web The M31 – M33 filament • extremely diffuse in bridge region (same low NHI in GBT and WSRT TP beams) Braun & Thilker 2004, A&A, 417, 421 GBT confirmation (30 min ON/OFF) wide-field WSRT data • the first detection of the “cosmic web”/ WHIM in HI emission

  35. Imaging the low-z Cosmic Web Cosmic Web and QSO absorption lines Braun & Thilker 2004, A&A, 417, 421 wide-field WSRT: M31-M33 filament QSO Abs. line data wide-field GBT: streams + CHVCs WSRT mosaic: disk + cores • composite NHI distribution from WSRT mosaic, GBT, wide-field WSRT • normalization from HIPASS BGC (Zwaan et al. 2003, AJ, 125, 2842) • good agreement with QSO absorption line data • the first image of a Lyman Limit absorption System

  36. Conclusions • M31 has rich HI environment of: tidal debris, halo components and a discrete cloud population • linewidth-mass relationship for discrete pop. suggests very strong DM dominance (MDM ~ 100 MHI) • total HI mass is modest, about 2% of M31 HI mass: ~108 MSun • total HII mass is more substantial; ~ 109 MSun if x = 0.9 and possibly much more in the halo component (x > 0.99 !) • total detected extent, R ~ 150 kpc, but centrally concentrated with h~ 25 kpc (and not s~150-200 kpc) • composite NHI consistent with QSO abs. line data at z=0; here are images of the absorbers! • kinematic study of the cosmic web is now in reach!

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