THINGS, Giants and dwarfs
António Portas - CAR, UK
Elias Brinks - CAR, UK
Mercedes Filho - CAUP, Portugal
Antonio Usero - OAN, Spain
THINGS team
Cookie seminar - CAUP - September 2009
THINGS, Giants and dwarfs
António Portas - CAR, UK
Elias Brinks - CAR, UK
Mercedes Filho - CAUP, Portugal
Antonio Usero - OAN, Spain
THINGS team
“Cookie Monster” seminar - CAUP - September 2009
Overview
• The THINGS’ things
• The Edges of THINGS: spiral analysis
• The Edges of THINGS: a dwarf perspective
• The HI z-distribution: GALMOD
• NGC 765: A HI disturbed giant ?
• Future work
The THINGS’ things : The HI Nearby Galaxy Survey
• High resolution (6" x 5 km s-1, or better) HI
maps of a sample of 34 nearby galaxies.
• ~ 400 hours of VLA B,C & D array data +
100 hours archive data
The bigger picture
• Spiral galaxies show sharp edges in their HI
disks.
• Origin edges: instrumental limitation, external
ionization, or running out of matter ?
• At low column densities < 1016 atoms cm-2 we
should see a filamentary structure connecting
galaxies ->The “cosmic web”.
• Push the detection of HI in galaxies
• What limits the size of a galaxy ?
• ionization -> extragalactic ionization field
• limited amount baryonic matter -> galaxy
formation
Millenium simulation
The Edges of THINGS: HI in the outer parts of spiral
galaxies
António Portas, Elias Brinks, Antonio Usero, Fabian Walter, W. J. G. de Blok and Robert C.
Kennicutt, Jr., 2009, AAS (in preparation)
NCC 925
NCC 3184
NCC 3198
NCC 3627
NCC 3521
NCC 3351
NCC 7793
NCC 5194
NCC 7331
The Edges of THINGS: HI in the outer parts of spiral
galaxies
Radial profiles: NGC 3351
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The Edges of THINGS: HI in the outer parts of spiral
galaxies
Sérsic parameterization
• Broadly use to fit luminosity profile of early type galaxies
•We use a Sérsic inspired parameterization, where we normalize the radius by ri .
−(1−n)
I(r) = I(0)e
r
ri
”1/n
I(0) - central column density
n
slope
ri - inflection point
log10 column density (cm-2)
22
“
21
20
19
18
17
n=0.17
n=0.14
n=0.22
16
0
5
10
15
Radius (kpc)
20
25
The Edges of THINGS: HI in the outer parts of spiral
galaxies
Sérsic parameterization
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The Edges of THINGS: HI in the outer parts of spiral
galaxies
22
2
21
1
log10 (Msun pc-2)
log10 column density (cm-2)
Results
20
925
3184
19
3198
3351
18
3521
0
NGC 925
NGC 3184
-1
NGC 3198
NGC 3351
NGC 3521
-2
NGC 3627
3627
NGC 5194
5194
17
-3
7331
NGC 7331
NGC 7793
7793
16
-4
0
0.5
1
1.5
Radius/ri
2
2.5
0
0.5
1
1.5
2
Radius/ri
We propose to set the HI radius of a isolated spiral galaxy at 1.2 ri ~ 5 x 1019 atoms cm-2 or
0.4 M sun pc-2
2.5
The Edges of THINGS: HI in the outer parts of spiral
galaxies
Global scenario of an HI profile
log10 column density (cm-2)
22
Region I
21
Region II
Region III
20
19
18
17
16
0
5
10
15
20
25
Radius (kpc)
Transition from Region I - II defined around ri can not be explained by external
ionization agent.
The Edges of THINGS: HI in the outer parts of spiral
galaxies
Simulations (Sommer-Larsen priv. comm.)
22
22
-1
Vc = 245 km s
Vc = 110 kms-1
21
20
log10 NHI
log10 NHI
21
19
18
HI
HI + warm
20
19
HI
HI+warm
18
17
17
0
5
10
15
radius kpc
20
25
30
0
5
10
15
20
radius kpc
ionization by an external agent becomes important at a column density of 1018 atoms cm-2
25
The Edges of THINGS: a dwarf perspective
António Portas, Elias Brinks, Antonio Usero , Fabian Walter , W. J. G. de Blok and Robert C.
Kennicutt, Jr. (in preparation)
DDO154
M81 a
DDO53
M81 b
NGC 1569
HO I
NGC 2366
HO II
NGC 2976
IC 2574
NGC 4214
The Edges of THINGS: a dwarf perspective
Radial profiles
D53
HO I
22
22
21
Log NHI in cm-2
Log NHI in cm-2
21
20
19
18
20
19
18
17
0
1
2
3
17
4
0
1
2
Radius in kpc
NGC1569
4
NGC2976
22
22
21
21
Log NHI in cm-2
Log NHI in cm-2
3
Radius in kpc
20
19
18
20
19
18
17
17
0
1
2
3
4
Radius in kpc
5
6
7
8
0
1
2
3
Radius in kpc
4
5
6
The Edges of THINGS: a dwarf perspective
Scale-lengths relations
10
y = 0.7247x
R2 = 0.12
r25 (arcmin)
8
6
ri
4
RHI
2
spirals PA
dwarfs PA
Linear (FIT)
0
0
2
4
6
ri (arcmin)
8
10
1.37 r25
1.6 r25
The HI z-distribution: GALMOD
Spirals vs dwarfs
The HI z-distribution: GALMOD
Spirals vs dwarfs
Thin HI disk
Thick HI disk
The HI z-distribution: GALMOD
PA = 220º
INCL = 60º
144:1 ratio
vdisp= 6 km/s
36:1 ratio
vdisp= 10 km/s
7:1 ratio
vdisp= 10 km/s
72:1 ratio
vdisp= 6 km/s
15:1 ratio
vdisp= 6 km/s
PA = 45º
INCL = 75º
144:1 ratio
vdisp= 6 km/s
NGC 765: a disturbed HI giant ?
António Portas, Elias Brinks, Mercedes Filho, Antonio Usero and Eleanor Dyke, 2009 (submitted), MNRAS
NGC 765: a disturbed HI giant ?
A multi wavelength perspective
VLA radio
VLA continuum
INT optical
Chandra X-ray
GALEX uv
NGC 765: a disturbed HI giant ?
Multi-wavelength perspective : HI + optical
• Distance ~72 Mpc z~0.017
• Diameter ~ 280 kpc
• HI to optical ratio ~12
• MHI ~ 4 x 1010 Msun
• Unresolved central area
• Inner disk has 3 spiral arms
UGC 1453
• Outer disk characterized by HI
compact regions
NGC 765: a disturbed HI giant ?
Compact HI regions
•Size range from 10 to 40 kpc
•HI mass range from 108-9 Msun
•10 % of HI mass of galaxy
NGC 765: a disturbed HI giant ?
Compact HI regions
Origin:
• minor merger equivalent to (Sgr)
dwarf galaxy;
• cosmological gas filaments
accretion;
• internal distortions originated after
several rotation of spiral arms;
Future work
• Allocated 10 hours in VLA C-array in NGC 765. Higher
resolution data will allow a better understanding of HI compact
regions.
• GALMOD optimization of scale heights and velocity
dispersions. This will sustain the edge analysis on the dwarfs.
• Similar edge analysis in the upcoming LITTLE THINGS (Local
Irregular That Trace Luminosity Extremes THINGS)
• THINGS website where high resolution moment 0, 1 & data
cubes are available for download :
http://www.mpia.de/THINGS/Data.html