Bielby & Shanks 2007 MNRAS submitted
ROSAT sample of 30 low z clusters Chanda sample of 38 z=0.3 clusters
Interstellar Neutral Hydrogen Emission Structure and Radio
Frequency Continuum Radiation (WMAP) Signals
• Gerrit L. VerschuurPhysics DepartmentUniversity of Memphis
Hydrogen line (HI) data side-lobe corrected
• H-line is a spectral signature at 1,420 MHz or 21-cm wavelength of hydrogen gas between the stars
• Used the Leiden-Dwingeloo All Sky Survey• Hartmann & Burton (1997)• Sidelobe corrected• Plus some from LAB Survey - Kalberla et al. (2005)
• All data will be displayed in galactic coordinates - longitude (l) & latitude (b)
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Galactic longitude (°)
Galactic latitude (°)
20 40 60 80Whole_area__20_to__10_rs
Target Area -20 to -10 km/s
Low velocity
I used 25 HI maps like this to explore the relationship betweenHI and WMAP structure in this area of sky
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0.02.55.07.510.012.515.017.520.022.525.027.5Whole_area__130to_1290_rs
Whole area -130 to -120 km/s 1:28 @ 2
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WMAP pruned, raw data .08 : 0.22 @ 0.03
WMAP +ve contours 0.08 : 0.22 @ 0.02 mK
Overlay WMAP +ve contours on HI inverted gray-scale map
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0.02.55.07.510.012.515.017.520.022.525.027.5Whole_area__130to_1290_rs
Whole area -130 to -120 km/s 1:28 @ 2
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WMAP pruned, raw data .08 : 0.22 @ 0.03HI -130 to -120 km/s
In general, anomalous vel. HI are in the proximity of WMAP peaks.
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Galactic longitude (°)
Galactic latitude (°)
0 10 20K.km/s
HI -130 to -120 km/s
Inverted grayscale - HI Contours WMAP peaks
Peak at -126 km/s
Peak at -116 km/s
A possible model -1
Depending on how the line-of-sight intersects the colliding HI features, we may expect to observe alignment of WMAP peaks and HI peaks, or offset peaks
Intercloud plasma
(a) (b)
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Galactic longitude (°)
Galactic latitude (°)
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Galactic longitude (°)
Galactic latitude (°)
V= - 118 km/s v= - 87 km/s
Calculate expected number of associations
• Probability that a given WMAP peak will lie within a distance r of an HI peak located in an area A is:
• r2 A-1
• But we have many WMAP peaks and very many HI peaks at different velocities
Calculate expected number of associations
• Nwpeaks = 33 consider the 33 brightest• Nhpeaks ~ 550/3 ~ 183 visible over 3 maps on
average• N= number of cases where direct
association is expected in this area, A (=4,800 square degrees)
• N = r2 A-1 NWpeaks NHpeaks.
Not chance coincidenceTable
Number of Associations between HI and ILC Peaks: Prediction versus Observation
Target Area Comparison Area Predicted Observed Predicted Observed Direct Association 0.2 10 0.1 0 (within 0.°2) Close offsets 5.1 11 5.9 4 (within ~ 1 deg) (within ~ 1.5 deg) ______________________________________________________________
What did this show?
• For the 1st time, high velocity and intermediate velocity HI structures have been found to be directly associated
• They both appear to be associated with a lack of low-velocity HI
• All three are associated with enhanced continuum emission
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Galactic latitude (°)
0 2 4 6l145_b60_area__93to_91_kms_rs
l=145, b=60 area -93 to -91 km/s
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HVC MI neutral hydrogen data
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5
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Galactic longitude (°)
Galactic latitude (°)
HVC MI -140 to -100 km/s 5 : 100 @ 10
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Galactic longitude (°)
Galactic latitude (°)
0 25 50 75 100K.km/s
HI v = -140 to -100 km/s
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Galactic longitude (°)
Galactic latitude (°)
8 18 28 38 48 58 68 78 88 98Cloud_MI__140to_100_rs
v = -140 to -100 km/s
H
HI - inverted gray-scale
WMAP +ve contours
A possible model -1
Depending on how the line-of-sight intersects the colliding HI features, we may expect to observe alignment of WMAP peaks and HI peaks, or offset peaks
Intercloud plasma
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Galactic latitude (°)
This lead to a prediction in November, 2006 HVC MII will be associated with continuum emission
HVC MI
Excess softX-ray emissionHerbstmeier et al.
HI contours
Testing a prediction HVC MII would show something similar to HVC MI
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HVC MII -70 to -60 km/s 2 : 30 @ 2
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HVC MII v = -70 to -60 km/s
Using WMAP ILC data obtained in December, 2006:
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HVC MII v = -70 to -60 km/s
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194 192 190 188 186 184 182 180
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10 20 30Comp_area_2___70__x_rs
MII zoom -70 to -60 km/s 2 : 30 @ 2
Soft X-ray excesses
H excess
At the location of the WMAP peaks, the HI profiles are double peaked
Overlay WMAP +ve contours on HI inverted gray-scale map
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0.02.55.07.510.012.515.017.520.022.525.027.5Whole_area__130to_1290_rs
Whole area -130 to -120 km/s 1:28 @ 2
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WMAP pruned, raw data .08 : 0.22 @ 0.03HI -130 to -120 km/s
In general, anomalous vel. HI are in the proximity of WMAP peaks.
7 24
Readily Identified Associations between HI & WMAP Peaks (~0.03mK to 0.06 mK)
HI maps made at 4 km/s intervals, each map covered a 2 km/s widthWMAP contours were plotted from 0.02 mK at 0.02 mK intervals
Galactic Coordinates of Area mapped
(°)
Area in Square degrees
Velocity rnage of HI maps
(km/s)
Number of weak WMAP
peaks in Area
Number with clearly
associated HI peak
Number of those closely aligned
128,-39 450 -94 to +22 14 12 4110, -38 300 -78 to +26 1 1145, -65 500 -82 to +18 2 2100, -55 450 -78 to +22 13 10 1235, -65 300 -74 to +10 1 0157, -52 400
-142 to + 110 4 3 1
40, 60 800 -94 to +14 5 4 150, 40 400 -98 to +38 13 11 250, -45 600 -70 to +22 16 8 3
30, -50 200 -154 to -78
-42 to +2 2 2Totals: 71 53 12
NOTES:1. It became immediately obvious that the weak WMAP peaks are associated with weak HI peaks. 2. All associations are closely spaced, slightly offset, unless otherwise indicated3. Velocity ranges of available maps determined by extent of HI emission inn specific areas.4. Area values not corrected for galactic latitude
5. The Target Area was also examined for this Table but there are too many associations to count, which is why I initially avoided the weak peaks and focussed on the brighter WMAP peaks. They more readily revealed information about interstelllar HI properties.
6. I have to hand several more areas plotted two months ago, to be examined later!
Overview
• Since December I have used WMAP data kindly provided by Gary Hinshaw and Wayne Landsman and compared those data with over 500 HI maps at 2 km/s intervals for small regions of sky.
• The pattern that has emerged is that when the WMAP peak is clearly associated with HI more than one HI feature is involved
• Collisions?
Conclusions: general
• Welcome Back to the Galaxy!
• WMAP small-scale structure may have a significant contribution from foreground features associated with HI structure
• It is possible that all the small-scale WMAP continuum emission structure has a Galactic origin
• By examining HI structure in the direction of WMAP continuum emission peaks at intermediate and high galactic latitudes the study of galactic HI is suddenly made very interesting
Suggestions for the future
• Convert young cosmologists to the study of interstellar structure
• . . . . before they get lost in the cosmos• Extend study to other areas of the sky - a vast
opportunity for new discovery• It is likely that plasma phenomena are key to
understanding interstellar structure • Invite plasma physicists to meet with
astrophysicists studying interstellar structure to create common ground
Reports
• Further Evidence for the Critical Ionization Velocity Signature in Interstellar Neutral Hydrogen Emission Profiles
• IEEE Transaction on Plasma Science - August 2007• This paper offers an explanation for the mechanism for
producing weak continuum emission at the interface between colliding HI features
• High Galactic Latitude Interstellar Neutral Hydrogen Structure and Associated High Frequency Continuum Emission
• Being reviewed for Astrophysical Journal
Acknowledgments
• Dap Hartmann & Butler Burton for providing the LDS All-Sky Survey data last century
• Wayne Landsman of the WMAP group for providing WMAP ILC data for the Target Area in a form I could use (uniform l-b grid)
• Butler Burton for his encouragement and valuable discussions
• Joan Schmelz for her encouragement, valuable discussions, critical readings of my MSs, comments on PPTs, and understanding of the key issues
• Tom Dame for his “holy grail” program using a data cube that allowed
me to make HI maps with ease • Richard Lieu and Jonathan Mittaz for helpful discussions
Hole in local HI at the location of the HI peaks at high and intermediate velocities
This has never before been observed
All are associated with the WMAP peak116 114 112 110 108
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Galactic longitude (°)
Galactic latitude (°)
10 15 20 25 30K. km/s
v- -8 to +2 km/s