Galactic Center Positronium Search
We'd like to use TripleSpec to try to detect positronium H-alpha and Paschen-gamma.
TripleSpec (cookbook from palomar)
sensitivities should be ~19th mag in J band, 17th in K-band: it is more sensitive in the H-alpha line.
(these numbers assume 10 minute exposures, but we are probably limited to ~18th magnitude by sky)
Proposal draft for APO 3rd quarter 2008: apo_gcprop.txt
Zero magnitudes for J and K bands are given:
here
K = 666.7, J=1594
Our K sensitivity, then, is 666.7*10**(-17/2.512) = 114 microJanskys
J is 1594 * 10**(-18/2.512) = 108 microJanskys
so really the difference isn't that significant when you take into account sky background
Those measurements are for a continuum source, and they may be wrong. We also need to do these
calculations for a resolved line.
Source 4 below gives an expected flux to "the best known source of annihilation in the GC direction"
of F(H-alpha) = 5x10^-29 erg cm^-2 s^-1 Hz^-1 = 5 microJanskys
This source also recommends looking at GROJ1655-40, GRS1758-258
If there is any emission from a point source, then observing with APO is the right way to go. Otherwise,
our only real hope is to average over a number of observations.
Task list:
- Pick targets: Great Annihilator? Empty region? Ask John
- Determine limits INTEGRAL information gives us
- Data mine?
Source list:
- Great Annihilator
- GROJ1655-40
- GRS1758-258
- 17 43 54.83 -29 44 42.6
- 16 54 00.14 -39 50 44.9
- 18 01 12.30 -25 44 36.0
TripleSpec A0 calibrators
Top choices:
- HD 159008,f|S|A0V, 17:32:50.71, -13:28:55.5, 7.24, 2000
- HD 164333,f|S|A0V, 18:00:55.98, -8:28:34.6, 10.04, 2000
- HD 155379,f|S|A0V, 17:12:13.62, -25:15:18.5, 6.50, 2000
- HD 164638,f|S|A0V, 18:03:09.84, -27:06:51.6, 10.58, 2000
Relevant papers:
- INTEGRAL central radian measurements
- All-sky distribution of 511 keV
- Characteristic Lines of Positronium
- Proposal for detection
- Bally and Leventhal: Great Annihilator
- Search for Positronium in Great Annihilator
For data mining: There are SINFONI integral field spectrograph Ks-band observations of the GC, which means that there should be a lot of identically-sampled spectra that can be averaged over to attempt to get at the Pa-Gamma line. Otherwise, we need to start looking at Keck/VLT/Gemini spectra; those will be the deepest.
ESO Data Archive
List of public (and private) SINFONI observations of GC
Cumulative Exposure Time / Instrument / Filter: |
SCIENCE - SINFONI - |
23 | h |
41 | min |
54 | s |
SCIENCE - SINFONI - H+K |
29 | h |
15 | min |
33 | s |
SCIENCE - SINFONI - K |
36 | h |
35 | min |
33 | s |
CALIB - SINFONI - K |
0 | h |
0 | min |
20 | s |
ACQUISITION - SINFONI - H+K |
0 | h |
2 | min |
6 | s |
ACQUISITION - SINFONI - K |
0 | h |
0 | min |
43 | s |
Total |
89 | h |
36 | min |
10 | s |
|