Transcript Gamma Ray Burst Lensing Limits on Cosmological Dark Matter

Gamma Ray Burst Lensing Limits
on Cosmological Dark Matter
Robert J. Nemiroff (Michigan Tech)
Primary Collaborators:
Jay P. Norris (NASA), Jerry T. Bonnell
(USRA), Gabriela Marani (GMU)
Gamma Ray Burst Lensing Limits on
Cosmological Dark Matter
Overview of:
•
•
•
•
Gamma Ray Bursts
Gravitational Lensing
Cosmological Dark Matter
Gamma Ray Burst Lensing Limits on Cosmological Dark
Matter
– Searches, Present Limits
• Future Missions
– Swift, GLAST, theoretical usefulness
Gamma Ray Bursts
• Intense flashes of gamma rays
•
•
•
•
•
– Last from milliseconds to minutes
– Location unpredictable: occur all over the sky
Discovered by accident in 1960s
Seen now by satellites across Solar System
BATSE on CGRO (1991-2000) saw most, faintest
Distance “Great Debate” at Smithsonian in 1995.
GRBs now known to occur at cosmological
distances
Optical Transients (OTs) and redshifts first
recorded in 1997
Gamma Ray Bursts
Sky Map (BATSE, final)
Credit: G. Fishman, et al., BATSE, CGRO, NASA
Gamma Ray Bursts
A GRB 000301C Symphony
Astronomy Picture of the Day
2000 March 14
•
Telescopic instruments in Earth and space are still tracking a
tremendous explosion that occurred across the universe. A
nearly unprecedented symphony of international observations
began abruptly on March 1 when Earth-orbiting RXTE, Sunorbiting Ulysses, and asteroid-orbiting NEAR all detected a 10second burst of high-frequency gamma radiation. Within 48
hours astronomers using the 2.5-meter Nordic Optical
Telescope chimed in with the observation of a middlefrequency optical counterpart that was soon confirmed with the
3.5-meter Calar Alto Telescope in Spain. By the next day the
explosion was picked up in low-frequency radio waves by the
by the European IRAM 30-meter dish in Spain, and then by the
VLA telescopes in the US. The Japanese 8-meter Subaru
Telescope interrupted a maiden engineering test to trumpet in
infrared observations. Major telescopes across the globe soon
began playing along as GRB 000301C came into view, detailing
unusual behavior. The Hubble Space Telescope captured the
above image and was the first to obtain an accurate distance to
the explosion, placing it near redshift 2, most of the way across
the visible universe. The Keck II Telescope in Hawaii quickly
confirmed and refined the redshift. Still, no one is sure what
type of explosion this was. The symphony is not over - oddly no
host galaxy appears near the position of this explosion. Will one
appear as the din of the loud fireball fades?
Credit: Andrew Fruchter (STScI) et al., STIS, HST, NASA
Gamma Ray Bursts
Aside: Sky Monitoring: CONCAM
http://concam.net
Six nodes currently active, 3 more already deployed
X
Y
X
X
Gamma Ray Bursts
Aside: Sky Monitoring: CONCAM
• Here is the sky movie
from Mauna Kea on
the night of 2001
November 18.
• Easily visible are stars,
planets, meteors, the
Galactic Plane, and
zodiacal light
Gravitational Lensing
Gravity attracts even light
•
•
•
•
•
•
First predicted in 1800s
First detected 1919 by Eddington for Sun
QSO lensing first detected 1979
Cluster of Galaxy lenses: 1986
Microlensing: 1993
GRB lensing: 20??
Cosmological Dark Matter
Big Mystery
• Modern cosmology driven by observations
• Defining observations:
– cluster motions, spiral rotation curves, nucleosynthesis,
galaxy clustering, distant supernovae and the cosmic
microwave background
• Standard Cosmological Paradigm (new!):
– Omega_lambda=0.73
– Omega_CDM=0.23
– Omega_baryon=0.04
• What makes up dark energy, dark matter, dark baryons?
Gamma Ray Burst Lensing Limits
on Cosmological Dark Matter
Types of Proposed GRB Lensing:
• macrolensing (Galaxy-mass lens)
– Nemiroff et al., ApJ, 1994
• millilensing (globular cluster mass lens)
– Nemiroff et al., PRL, 2001
• microlensing (stellar mass lens)
– Paczynski., ApJ, 1986
Gamma Ray Burst Lensing Limits
on Cosmological Dark Matter
• Femtolensing (10-13 - 10-16 Mo)
– Gould, A. 1992, ApJ
• Picolensing (10-15 - 10-7 Mo)
– Nemiroff & Gould, 1995, ApJ
• Nanolensing (~10-5 Mo)
– Walker & Lewis, 2003, ApJ
Gamma Ray Burst Lensing Limits
on Cosmological Dark Matter
• Search for echos
of GRBs in
BATSE time
series
• Searched most
BATSE GRBs
• No good
candidates found
Time from trigger, seconds
Gamma Ray Burst Lensing Limits
on Cosmological Dark Matter
• For detection, millilens must create
– second image within detectable flux ratio
– second image within detectable time boundaries
• Gravitational Lens Detection Volume:
– Lens cannot be too far from axis or flux ratio drops below
detectability
– Lens cannot be too far from axis or time delay increases beyond
detectability
– Lens cannot be too close to axis or time delay decreases beyond
detectability
Gamma Ray Burst Lensing Limits
on Cosmological Dark Matter
• No lens echoes
detected
• Many lens
echoes expected
if dark matter
clumped into
canonical mass
aggregates.
Future Missions
Swift
• Swift satellite (NASA)
• Scheduled launch:
12/2003
• Observe >200 GRBs,
many with redshifts
• 5 times more sensitive
than BATSE
Future Missions
GLAST
• GLAST satellite
(NASA)
• Scheduled launch:
2006
• >200 GRBs/yr
Future Missions
Theoretical Potential
GRBs the most variable objects visible in the
distance universe
– untapped potential for known objects
•
•
•
•
macrolensing: galaxy formation (high z)
millilensing: AGN formation (high z)
microlensing: star density (high z)
picolensing, nanolensing, femtolensing:
– unique path to explore low mass universe