THE STELLAR AND GASEOUS HALO OF M51 Aaron E. Watkins In - - PowerPoint PPT Presentation

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THE STELLAR AND GASEOUS HALO OF M51 Aaron E. Watkins In collaboration with: J. Christopher Mihos 1 Paul Harding 1 Matthew Bershady 2 1) Case Western Reserve University 2) University of Wisconsin -- Madison INTRODUCTION TO M51 Historically

SLIDE 1

THE STELLAR AND GASEOUS HALO OF M51

Aaron E. Watkins

In collaboration with:

J. Christopher Mihos1

Paul Harding1 Matthew Bershady2

1) Case Western Reserve University 2) University of Wisconsin -- Madison

SLIDE 2

INTRODUCTION TO M51

Historically important galaxy

pair -- spirals, interactions, gas tidal response, &c.

Nearby: D ~ 8.5 Mpc
About the system:

– Disk mass ratio ~1/3 -- 1/2 (e.g.,

Smith et al. 1990, Salo & Laurikainen 2000, &c.)

– Gas-rich Sc disk (M51a) + gas-

poor SAB disk (M51b)

Hubble Heritage Archive M51a M51b

SLIDE 3

OBSERVATIONS

Full mosaic ~2°x2°

(focal plane f.o.v. ~1.5°x1.5°)

Exposure times:

31x1200s (B), 39 x 900s (V)

μlimit ~ 30

mag/arcsec2 (B)

Burrell Schmidt Telescope (recall Chris Mihos' talk)

This one

SLIDE 4

East/West

Streams:

B-V~0.75 (same

as M51b)

coherent (disk
rigin), caustic?
μ~25.5--26
L

, B ⊙ ~ 4x107

(each)

RESULTS

Watkins + 2015 10´ (~25 kpc)

SLIDE 5

Northwest Plume:
B-V~0.8 (color of
uter disks;

Watkins+14, 16)

Still coherent

despite length (~30 kpc end to end)

μ~27.5--28
L

, B ⊙ ~ 108

RESULTS

Watkins + 2015 10´ (~25 kpc)

SLIDE 6

Northeast Plume:
μ~29, no good

color constraint

Related to

'crown'?

South Plume
μ~29
Accreted?
Both L

, B ⊙ ~ 5x106

RESULTS

Watkins + 2015 10´ (~25 kpc)

SLIDE 7

HALO GAS CONTENT

System surrounded by

tidally stripped gas

No obvious stellar

counterpart to any extended HI

2015: follow-up deep

narrowband imaging with Burrell Schmidt

Interesting discovery...!

21 cm observations from Rots + 1990

SLIDE 8

Hα NARROWBAND IMAGE

Watkins + 2018

SLIDE 9

Hα NARROWBAND IMAGE

Watkins + 2018

32 kpc

SLIDE 10

SPARSEPAK SPECTRUM

Watkins + 2018

Vhel ~ 640 km/s VM51~460 km/s

SLIDE 11

LINE RATIOS

log(NII / Hα) ~ +0.17
log(SII / Hα) ~ -0.10
log(OI / Hα) ~ -0.77

BPT Diagrams from: Singh + 2013

SLIDE 12

FATE OF GAS IN MERGERS

M51, ionization only
"Hanny's Voorwerp":

similar origin object (?), but embedded HII regions!

In some AGN hosts,

halo stars might form literally "in-situ"

IC 2497 Green = OIII 5007 Orange = Hα+NII

SLIDE 13

SUMMARY

In the M51 system, the "stellar halo" observed

with deep imaging appears mainly to originate with both galaxies' disks

Gaseous tidal debris is also abundant, and

energetic phenomenon (AGN? shocks?) ionized a swath of it

Energetic winds/shocks: how often can this

THE STELLAR AND GASEOUS HALO OF M51

Aaron E. Watkins

In collaboration with:

Paul Harding1 Matthew Bershady2

INTRODUCTION TO M51

pair -- spirals, interactions, gas tidal response, &c.

Smith et al. 1990, Salo & Laurikainen 2000, &c.)

poor SAB disk (M51b)

OBSERVATIONS

(focal plane f.o.v. ~1.5°x1.5°)

31x1200s (B), 39 x 900s (V)

mag/arcsec2 (B)

Streams:

as M51b)

(each)

RESULTS

Watkins+14, 16)

despite length (~30 kpc end to end)

RESULTS

color constraint

'crown'?

RESULTS

HALO GAS CONTENT

tidally stripped gas

counterpart to any extended HI

narrowband imaging with Burrell Schmidt

Hα NARROWBAND IMAGE

Hα NARROWBAND IMAGE

32 kpc

SPARSEPAK SPECTRUM

Vhel ~ 640 km/s VM51~460 km/s

LINE RATIOS

FATE OF GAS IN MERGERS

similar origin object (?), but embedded HII regions!

halo stars might form literally "in-situ"

SUMMARY

with deep imaging appears mainly to originate with both galaxies' disks

energetic phenomenon (AGN? shocks?) ionized a swath of it

energy injection form literally "in-situ" halo stars?