1. No category

The Fate of the Neutral
Gas in Group Environments
Tobias Westmeier (ICRAR / UWA)
International
Centre for
Radio
Astronomy
Research
Introduction
New Brunswick, 16 / 03 / 2015
Westmeier – Neutral Gas in Group Environments
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Introduction
★ Gas stripping in high-density environments
HCG 44 (Serra et al. 2013)
▶ Removal of neutral gas through
Tidal interaction
● Ram-pressure stripping
●
▶ Effect on H Ⅰ mass function and star formation
Kenney et al. (2004)
Kilborn et al. (2006)
NGC 4522
NGC 3783 group
New Brunswick, 16 / 03 / 2015
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Introduction
★ Increasing evidence for ram-pressure
stripping in group environments
NGC 4414
de Blok et al. (2014)
▶ Coma Ⅰ group
H Ⅰ deficiency
● NGC 4414
●
(García-Barreto et al. 1994)
(de Blok et al. 2014)
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Introduction
★ Increasing evidence for ram-pressure
stripping in group environments
▶ Coma Ⅰ group
H Ⅰ deficiency
● NGC 4414
●
(García-Barreto et al. 1994)
(de Blok et al. 2014)
Spekkens et al. (2014)
▶ Local Group
H Ⅰ deficiency
● Pegasus DIG
●
(Grcevich & Putman 2009; Spekkens et al. 2014)
(McConnachie et al. 2007)
★ Implications
▶ n IGM ≈ 10−6…10−4 cm−3
▶ Quenching of star formation (Slater & Bell 2014)
Slater & Bell (2014)
New Brunswick, 16 / 03 / 2015
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Deep Parkes H Ⅰ Survey
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Deep Parkes H Ⅰ Survey
★ Targets
HPBW
▶ Northern Sculptor group
▶ Additional deep Hipass Ⅱ data of entire
Sculptor group region
247
45
253
★ Observations
▶ Parkes + MB receiver
▶ Survey area of 15° × 10°
▶ M H Ⅰ ≈ 105 M☉ × (d / Mpc)2
Deep Parkes
survey
300
▶ Θ = 14.4′
55
Hipass Ⅱ
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Deep Parkes H Ⅰ Survey
★ Results
HPBW
▶ 31 H Ⅰ detections
247
d = 2…15 Mpc
● log(M H Ⅰ / M☉) = 6.6…9.4
●
45
▶ 14 detections not in Hipass catalogue
253
5 due to velocity limit
● 8 new H Ⅰ detections of dwarf galaxies
● NGC 59 (Beaulieu et al. 2006)
●
▶ All H Ⅰ detections have (tentative)
optical counterpart in DSS / Galex
●
No intergalactic gas or “dark galaxies”
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55
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Deep Parkes H Ⅰ Survey
★ New H Ⅰ detections
▶ M H Ⅰ ≲ 108 M☉
▶ Compact, irregular
galaxies
▶ Lack of photometric
and spectroscopic
information
Images: DSS
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Deep Parkes H Ⅰ Survey
Westmeier et al. (in prep.)
★ Comparison: observation vs. simulation
▶ HIPASS H Ⅰ mass function (Zwaan et al. 2005)
▶ Too many high-mass galaxies
●
Model 1
M H Ⅰ ≳ 109 M☉
▶ Too few intermediate-mass galaxies
●
M H Ⅰ ≈ 107…8 M☉
▶ Similar outcome for Alfalfa H Ⅰ mass
function (Martin et al. 2010)
Model 2
Observation
★ Questions
▶ Is this result significant?
▶ Evidence for stripping of gas?
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Deep Parkes H Ⅰ Survey
★ Comparison: observation vs. simulation
Westmeier et al. (in prep.)
▶ Kolmogorov–Smirnov test
●
Cumulative H Ⅰ mass distribution
▶ Results
D ≈ 0.17
● p ≈ 31%
●
▶ The probability of a statistical fluctuation
creating a discrepancy greater than the
one observed is 31% if model and
observation were drawn from the same
H Ⅰ mass function
▶ Discrepancy not statistically significant
due to small sample size
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Deep ATCA
H Ⅰ Observations
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Deep ATCA H Ⅰ Observations
★ Targets
HPBW
▶ NGC 55, 300
▶ NGC 247, 253
247
45
★ Observations
253
▶ ATCA in EW 352 / 367 configurations
▶ Mosaics of 32 / 16 pointings
▶ N H Ⅰ ≈ 2 × 1019 cm−2
▶ Θ ≈ 1.5′ × 2.5′ (≙ 1…2 kpc)
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ATCA
targets
Westmeier – Neutral Gas in Group Environments
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55
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Deep ATCA H Ⅰ Observations
★ NGC 300
▶ Asymmetric H Ⅰ disc
Sharp drop in H Ⅰ column density in the south-east
● Steady, exponential decline of N H Ⅰ in the north-west
●
Westmeier et al. (2011)
plateau
exponential
sharp
drop
S
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Deep ATCA H Ⅰ Observations
★ Applying model of Haan &
Braun (2014)
▶ Strong kinematic signature of
ram pressure in outer disc
▶ NGC 300 moving mostly
perpendicular to disc plane
▶ Proper-motion vector in
agreement with H Ⅰ
morphology
New Brunswick, 16 / 03 / 2015
S. Haan
S. Haan
S. Haan
S. Haan
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Deep ATCA H Ⅰ Observations
★ Density of IGM in Sculptor group
▶ Model of Haan & Braun (2014)
●
NGC 300: n IGM vs. Δv
(S. Haan)
n IGM Δv 2 ≃ 1.2 cm−3 (km / s)2 = 1.2 TPa / kg
▶ For Δv = 100…200 km/s we get
●
n IGM ≃ 3–12 × 10−5 cm−3
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Deep ATCA H Ⅰ Observations
★ Density of IGM in Sculptor group
NGC 300: n IGM vs. Δv
▶ Model of Haan & Braun (2014)
●
(S. Haan)
n IGM Δv 2 ≃ 1.2 cm−3 (km / s)2 = 1.2 TPa / kg
▶ For Δv = 100…200 km/s we get
●
n IGM ≃ 3–12 × 10−5 cm−3
★ Comparison with Virgo cluster
▶ NGC 4330 (Vollmer et al. 2012)
n IGM Δv 2 ≃ 2500 cm−3 (km / s)2
▶ NGC 4522 (Vollmer et al. 2006)
●
n IGM Δv 2 ≃ 2000 cm−3 (km / s)2
New Brunswick, 16 / 03 / 2015
Images: VIVA survey
●
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Wallaby Early Science
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Wallaby Early Science
★ Wallaby early science observations with Askap–12
▶ 12+ antennas with Mk Ⅱ PAFs
▶ Full correlator capacity (36 beams, 304 MHz, 16 416 channels)
▶ Due to begin in 2016
Photo: Steve Barker, CSIRO
New Brunswick, 16 / 03 / 2015
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Wallaby Early Science
★ Wallaby early science observing strategy
▶ Observe ≈ 10 fields with t ≈ 56 h per field
▶ H Ⅰ emission of 6 500 galaxies
▶ ≈ 1.6 mJy rms, 30″ resolution
t = 560 h
Area too small
L. Staveley-Smith
Sensitivity too low
L. Staveley-Smith
New Brunswick, 16 / 03 / 2015
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Wallaby Early Science
★ Aims of Wallaby early science
▶ Global effects of environment
α ≈ −1.5
Zwaan et al. (2005)
H Ⅰ mass function
● Tully–Fisher relation
● H Ⅰ scaling relations
●
α ≈ −1.2
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Wallaby Early Science
★ Aims of Wallaby early science
▶ Global effects of environment
H Ⅰ mass function
● Tully–Fisher relation
● H Ⅰ scaling relations
● H Ⅰ deficiency and star formation
●
Based on data from Grcevich & Putman (2009)
Spekkens et al. (2014)
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Wallaby Early Science
★ Aims of Wallaby early science
HCG 44 (Serra et al. 2013)
▶ Global effects of environment
H Ⅰ mass function
● Tully–Fisher relation
● H Ⅰ scaling relations
● H Ⅰ deficiency and star formation
●
▶ Morphological studies of galaxies
Ram-pressure stripping
● Tidal streams
● Kinematic modelling and asymmetries
●
New Brunswick, 16 / 03 / 2015
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Summary
New Brunswick, 16 / 03 / 2015
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Summary
★ Environmental effects in Sculptor group
▶ Too many galaxies with MH Ⅰ ≳ 10⁹ M☉, too few with MH Ⅰ ≈ 10⁷⁻⁸ M☉
▶ Discrepancies not statistically significant due to small sample size
▶ Evidence for ram pressure in Sculptor group
morphological + model of Haan & Braun (2014)
● nIGM ≃ 10−5…10−4 cm−3
●
★ Wallaby early science
▶ Observations due to begin in 2016
Model 1
10 fields (Ω = 30 deg², z ≤ 0.26)
● 6 500 galaxies at 30″ resolution
●
▶ Systematic study of environmental effects on H Ⅰ gas
Model 2
Observation
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SoFiA
★ Source Finding Application (SoFiA)
▶ New 3D source finding pipeline
▶ Graphical user interface
▶ Novel algorithms tailored to H Ⅰ surveys
●
●
●
●
●
Smooth + clip finder
CNHI finder
2D–1D wavelet filter
Reliability calculation
Busy Function
(Serra et al. 2012)
(Jurek 2012)
(Flöer & Winkel 2012)
(Serra et al. 2012)
(Westmeier et al. 2014)
▶ Paper
●
Serra, Westmeier, et al., 2015, MNRAS, 448, 1922
▶ Download
GitHub: https://github.com/SoFiA-Admin/SoFiA/
● Wiki, documentation, bug reports, feature requests
●
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Busy Function
★ The Busy Function
▶ B(x) = (a / 4) × [erf(b₁ (w + x − xe)) + 1] × [erf(b₂ (w − x + xe)) + 1] × [c (x − xp)n + 1]
▶ Purpose
Fit (asymmetric) double-horn profiles of galaxies
● Measure galaxy parameters: line width, peak
flux, integrated flux, radial velocity, etc.
●
▶ More accurate than direct measurement
▶ Paper
●
Westmeier et al., 2014, MNRAS, 438, 1176
▶ Fitting software
BF_dist (by R. Jurek)
● https://code.google.com/p/busy-function-fitting/
● busyfit (by T. Westmeier)
● http://www.atnf.csiro.au/people/Tobias.Westmeier/tools_software_busyfit.php
●
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Thank You!
P 
A 
SFA
B F
B. S. Koribalski
M. Meyer
A. Musaeva
D. Obreschkow
A. Popping
A. Wright
T. Young
R. Braun
B. S. Koribalski
H. Courtois
L. Flöer
N. Giese
J. M. van der Hulst
R. Jurek
B. S. Koribalski
M. Meyer
A. Popping
P. Serra
L. Staveley-Smith
B. Winkel
R. Jurek
B. S. Koribalski
D. Obreschkow
L. Staveley-Smith
R 
S. Haan
New Brunswick, 16 / 03 / 2015
H Ⅱ
M. Calabretta
R. Jurek
B. S. Koribalski
M. Meyer
A. Popping
L. Staveley-Smith
I. Wong
Westmeier – Neutral Gas in Group Environments
W
B. Koribalski
L. Staveley-Smith
+ the entire
Wallaby team
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