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

The M31 HI Environment

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)

Modeling the Cosmic Web

high res. num. sim. predict cosmic web of filaments

between galaxies

apparent correspondence with QSO absorbers

Dave et al. 1999, ApJ 511, 521, 2001, ApJ 552, 473

Modeling the Cosmic Web

strong (density-dependent) evolution with cosmic

epoch

collapse of over-dense regions yields greater

proportion of WHIM (z=0)

Dave et al. 1999, ApJ 511, 521

WHIM

DLALy-forest

(Ly-limit)

Modeling the Cosmic Web ~30% baryons in galaxies~30% baryons in galaxies ( @ z = 0 )

•association with QSO absorbers with NHI =

1018 – 1022 cm-2

~30% baryons in warm-hot inter-galactic ~30% baryons in warm-hot inter-galactic

medium (WHIM)medium (WHIM)

•condensed, shock-heated phase: T ~ 105 –

107 K


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~30% baryons in diffuse inter-galactic medium

•diffuse, photo-ionized phase: T ~ 104 K


1012 – 1014 cm-2

decreasing (micro- not macro-) neutral fraction decreasing (micro- not macro-) neutral fraction

with Nwith NHIHI

•~1% at NHI = 1017 cm-2, < 0.1% at NHI = 1013

cm-2

Hierarchical Galaxy Formation and the

“Missing Low Mass Companions”

high resolution numerical simulations predict an an

order of magnitudeorder of magnitude moremore low mass satellites than

observed with vc < 30 km/s: n(M) ~ M-2

Klypin et al. 1999, ApJ 522, 82Moore et al. 1999, ApJ 524, L19

Mini-halo Modeling

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

Kep

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Kepner et al. 1997, ApJ 487, 61


evolutionary and mass sequence

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

Sternberg, McKee & Wolfire 2002, ApJS 143, 419

“Missing Low Mass Companions”Mini-halo Modeling

WSRT Wide-field HI SurveyBraun, 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

• 17 mJy/Beam (at V = 17 km/s), cf. HIPASS =14

mJy/Beam

• NNHIHI = 4 x 10 = 4 x 101616 cm cm-2-2 for emission filling the beam (10

kpc at 700 kpc)

(cf. HIPASS NHI ~ 4 x 1017 cm-2 in 15 arcmin

beam)

Galactic CHVCs Magellanic Stream and Wright’s HVC complex circum-galactic HI clouds and streamscircum-galactic HI clouds and streams of M31

and M33 M31/M33 filament near systemic velocityM31/M33 filament near systemic velocity

Dirty Channel Maps

WSRT Wide-field HI Survey

Cleaned Channel maps


Braun & Thilker 2004, A&A, 417, 421

•> 100 newly detected compact features•Mag. Stream apo-galacticon tail, Wright’s Cloud•faint, compact pop. centered on M31 systemic faint, compact pop. centered on M31 systemic velocityvelocity•M31/M33 filament near systemic velocityM31/M33 filament near systemic velocity, NHI ~ 4x1017cm-2 (peak)


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•> 100 newly detected compact features•Mag. Stream apo-galacticon tail, Wright’s Cloud•faint, compact pop. centered on M31 systemic faint, compact pop. centered on M31 systemic velocityvelocity•M31/M33 filament near systemic velocityM31/M33 filament near systemic velocity, NHI ~ 4x1017cm-2 (peak)


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Dirty Channel Map


Dir

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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 ongoing fueling of

both M31 and M33both M31 and M33

(from GBT imaging)


Cleaned Channel Map


Dir

ty B

eam


•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 ongoing fueling of

both M31 and M33both M31 and M33

(from GBT imaging)

Green Bank Telescope wide-field HI imaging of

M31Thilker, 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

• 2 kpc x 1 km/s res. over 95 x 95 kpc

• 6.6 mJy/Beam (at V = 18 km/s)

• NHI = 1.5 x 1017 cm-2 at 3 kpc resolution

extended rotation curve/warping outer HI edge, UV rad. field HI clouds and streamsHI clouds and streams !!!!!!

V = 36 km/s

GBT wide-field HI imaging of M31

V = 72 km/s

GBT wide-field HI imaging of M31

GBT wide-field HI imaging of M31Thilker et al. 2004, ApJL, 601, L39

Detection of three distinct HVC populations

1.1. tidal streamstidal 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)

2.2. diffuse filamentsdiffuse filaments and halo centered on M31

systemic velocity, possible interface to the cosmic

web

3.3. concentration of faint, compact HVCsconcentration 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

WSRT HI mosiac of M31Braun, Corbelli, Thilker & Walterbos 2002 & 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

• 1.4 mJy/Beam (at V = 2 km/s)

• NHI = 1.0, 3.5, 11 and 24 x 1018cm-2

@ 120, 60, 30 and 20” (V=20

km/s)

extended rotation curve / warping outer HI edge / UV radiation field CNM / WNM in disk circum-galactic HI clouds and streamscircum-galactic HI clouds and streams

WSRT HI mosiac of

M31

• 50 pc x 2 km/s res. over

the 80 kpc disk

most detailed ISM cube

yet made

Bra

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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

Braun & Thilker 2004, in prep.

High resolution imaging of M31 CHVC Cores

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

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 V ~ 30 km/s•kinematic analysis now underway

Westmeier, Braun & Thilker 2004, in prep.


The M31 HVC Populations

•extensive tidal stream, halo and discrete HVC extensive tidal stream, halo and discrete HVC populationspopulations •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): = 150-200 kpc

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wide-field GBT data wide-field WSRT data

M33


The M31 discrete HVC Population (within 40 kpc radius)

•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 Here are the

missing low mass missing low mass

companions !!companions !!

wide-field GBT data



•connects VSYS of

M31 and M33 (170 kpc projected)

•continues in anti-M33 direction

•connects to ongoing fueling of ongoing fueling of both M31 and M33both M31 and M33 (from GBT imaging)

•relative distance and radial velocity imply M33 is likely approachingapproaching M31: makes tidal origin unlikely

Bra

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wide-field WSRT data

Imaging the low-z Cosmic Web

the first detection of the “cosmic web”/ WHIM in the first detection of the “cosmic web”/ WHIM in HI emissionHI emission

The M31 – M33 filament•extremely diffuse in bridge region

(same low NHI in GBT and WSRT TP beams)

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wide-field WSRT data GBT confirmation (30 min ON/OFF)


Cosmic Web and QSO absorption linesBraun & Thilker 2004, A&A, 417, 421

•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 datagood agreement with QSO absorption line data

the first image of a Lyman Limit absorption Systemthe first image of a Lyman Limit absorption System

WSRT mosaic: disk + cores

wide-field GBT: streams + CHVCs

wide-field WSRT: M31-M33 filamentQSO Abs. line data


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 ~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!

the extended hi environment of m31 robert braun (astron)

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