Transcript TAUVEX and AGNs

TAUVEX and AGNs
TAUVEX=Tel
Aviv University
UV Explorer
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Outline
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Background
Technical description
Projected performance
Scientific projects (AGNs)
Conclusions
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Why UV?
Background
Earth atmosphere
opaque to UV
UV range
Low sky background!
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IUE: all targets
Short history of UV astronomy
• UV range definition: 10 nm to 380 nm
• First observation: Sun, from V2 (US-NRL)
• First satellite: TD-1. Sky survey to ~9 mag
TD-1 starlight at 156.5 nm
in 3° bins (Sujatha et al. 2004)
• First spectroscopy: Copernicus
• Longest duration: IUE
• Most expensive: HST (only part is UV)
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Hyakutake
Generic UV Targets
Hale-Bopp 40 deg
SMC
• Comets
• Hot stars (high-mass,
evolved [WD])
• Galaxies: evolution
• Interstellar & InterGalactic matter
• AGNs
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TAUVEX history
Prime contractor: El-Op,
Electro-optical Industries
SRG=Spectrum Roentgen-Gamma
(incarnation I)
1989: chosen as 1st priority by ISA
1991: agreement to launch with SRG
1994: planned launch date
2000: delays with SRG; start
search for alternate launch
2003: ISA-ISRO agreement
2007: planned launch on GSAT-4
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The Indian
connection
• GSAT-4 to geo-synchronous orbit.
• Platform=technological demonstrator for
new generation of Indian communication
satellites.
• TAUVEX has a dedicated communication
channel of 1 Mbps, continuously.
• Satellite has fixed orientation w.r.t. the
Earth!
• To allow unrestricted
access to the sky, TAUVEX
is mounted on orientable
platform (MDP).
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Toward Earth
δ=+90º
δ=0º
MDP in launch orientation. MDP
motion is up to 180º from the
launch position, to -90≤δ≤+90
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TAUVEX basics
Technical description
•3x20cm RC telescopes
•~One-degree images
•Angular resolution ~7”
•UV “solar blind” sensitivity
•Unblocked area ~266 cm²(3x)
•On GSAT-4, sky scans
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TAUVEX: filter setup
CaF_2
cutoff
Includes geometric shadowing, 2 mirrors,
lenses+windows, filter trasmission & detector QE
Each telescope with 4position wheel
One position blocked
(shutter=CLS)
Three positions with filters
Filter arrangement
T1: SF1, SF2, BBF, CLS
T2: SF2, SF3, BBF, CLS
T3: SF1, NBF3, SF3, CLS
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TAUVEX performance
(and constrains)
Projected performance
15 cos  / sec
''
Drift rate:
“Pixel”=3 arcsec
Max. “no-smear” time=1/8 sec
Basic timescale for data frame
Simulated image
Object in FOV: 224 sec along
detector diameter at δ=0 (basic
exposure time)
High declination advantage!
11 pass)
(above 81º, more than 1500 sec per
Confusing magnitudes…
TAUVEX (monochrom atic) :
m  2.5 log f   21.175
GALEX :
AB  2.5 log f   5 log   2.40
[ f  ]  erg s -1cm -2 Angstrom -1
AIS 1 limit  20.0 (FUV)  17.10 monochroma tic
20.8 (NUV)  19.01
MIS 1 limit  22.6 (FUV)  19.70 monochroma tic
22.8 (NUV)  21.01
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TAUVEX vs. HST
Only operating UV instruments
at present are ACS & WFPC-2!
HST has:
•144x more collecting area
than TAUVEX
•70-700x better resolution
•400x smaller FOV (STIS)
•200-400x higher cost
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GALEX
AIS like TAUVEX single
pass (AB mag limit=18 mono)
GALEX NUV=
TAUVEX BBF
•GALEX launched April 2003 for all-sky UV survey
•GALEX (1x) and TAUVEX (3x) have similar collecting
areas and angular resolution
•GALEX has one 50-cm telescope and only two spectral
bands: FUV & NUV
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•GALEX operates only 1/3 of the orbit
TAUVEX - performance
• Exposure depth depends on:
– Dwell time of object in FOV (“exposure”)
– Level of background (Max count rate~100K/sec)
• Background is stray light: light scattered into the
detectors from sources external to the FOV
• Strongest source=Sun
• Operational solutions:
– Filter choice (solar spectrum)
– Sky strip selection
– Baffle extension
•Scattered into
baffle
•Reflected by
solar panels &
thrusters
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Sensitivity (best case)
SF-1
To Sun
BBF-best
case
SF-2
SF-3
BBF-worst
case
Equal-area projection of celestial hemisphere
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GALEX
vs.
• GALEX: DIS=80 sq.
degrees (~70 fields).
• Limiting AB=25 (1σ);
only small part done
yet
TAUVEX
• TAUVEX: DEC=+90
to +85 is equivalent
area to DIS
• Limiting mag’s (5σ)
for single scan are:
– SF1-3: 18-20
monochromatic
(AB=21-23)
– BBF: gain one mag
GALEX DIS field: Groth region,
14ksec exposure
To surpass GALEX DIS,
TAUVEX requires 10 scans of
the Polar Cap area! This is 1-2
months of observations. 17
TAUVEX science: AGNs
Projected results
• Detection (star-AGN photometric
separation)
• Rough redshift determination (UV
dropouts)
• Variability studies
Composite AGN spectrum (Telfer et al.
2002, ApJ 565, 773)
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How many low-z AGNs?
N
AGNs per square
degree, with z<1, to
different limiting
magnitudes.
Conclusion:
TAUVEX will find
significant numbers
of low-z AGNs
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GALEX AGNs: UV vs. optical colors
Red≡stars, green≡galaxies, light blue≡AGNs.+reddening GALEX+SDSS (Bianchi et al 2004)
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TAUVEX: UV+optical colors
Nearby AGNs (z<1)
Colors vs. redshift
Color-color plot
0
0 -0.1 -0.5
-0.2
-0.3
-0.4
-0.5
SF1-SF2
-1
Color (mag)
0.5
1
SF2-SF3
z
UV-UV
SF1-SF2
0.5
SF2-SF3
0
-0.5
1 2 3 4 5 6 7 8 9 10
U-B
B-V
-1
V-R
-1.5
10*z
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TAUVEX: UV+optical colors
UV-Optical
UV-Optical
0.8
0.5
z
0.6
B-V
0.4
0.4
0.3
0.2
V-R
z
0.2
0.1
0
0
0.5
0 -0.1
-0.5
SF1-SF2
-1
0
-0.2
-0.4
SF2-SF3
-0.6
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[email protected]<z<4, including Ly limit and Ly forest
AGN colors
Color-color
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SF1-SF2
0.4
SF2-SF3
1
0.2
U-B
0
-1 1 2 3 4 5 6 7 8
-2
B-V
V-R
0
1
0 -0.2
-0.4
-0.6
z/0.5
-1
-2
SF2-SF3
2
Color
UV-UV
z
SF1-SF2
Importance of simultaneous UV & optical measurements!
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Conclusions
TAUVEX offers similar performance to
GALEX, with important enhancements:
– Three simultaneous bands
– Five different filters (flexibility)
– Time-resolved photometry over a number of
time scales: 1/8 sec to 100s of sec for single
pass; revisits
Launch 20 February 2007
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TAUVEX on GSAT4: GENERAL VIEW
New features:
•Rotating plate
•Front radiator
•Extra baffle
•Extra shielding
•Thermal couplings
MDP
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Performance: SF-1
Equal-area plot, hemisphere
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Performance: SF-2
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Performance: SF-3
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Performance: BBF
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TAUVEX: detection system
Detection=(x, y, t)
Zigzag
(C)
CaF2
window
Strip (B)
Wedge (A)
(Approx. 700
“pixels” across
FOV)
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TD-1A & IUE
All-sky photometric survey
to 9 mag
Targeted mission:
spectroscopy
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TAUVEX science: stars & ISM
PAHs distribution?TD-1
B star UV spectrum
Use SF2 and NBF3
to measure the EW
of the ISM band
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TAUVEX science: galaxies
UV light
understand
physics of star-forming
processes, extinction
Late-type galaxies=good
targets
GALEX 1300 sec image
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TAUVEX science: galaxies II
Antennae galaxies
(NGC4039/4039):
importance of the UV
sensitivity to
establish the nature
of stellar populations
and determine the
full IMF
Hα
FUV, NUV
Optical (UBVRI)
Near-IR
Almoznino & Brosch 1998
Lyman cont`.
Hot stars (O,B,A)
Stars (F,G,K,M)
Stars (K, M)
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TAUVEX science: galaxies III
UV observations track the history of star formation in the
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last billion years
TAUVEX science:
UV-dropouts (cosmology)
Select z=1-2 galaxies
from UV dropouts
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TAUVEX: lab performance
Next
Edge
discharge
“Flat-field” (collimator)
More?
More?
Real image: distortion pattern
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GALEX surveys
SURVEY
Area
[deg]
Length
[Month]
Expos
[ksec]
m lim (AB)
log
#Gals
Volume
<z>
Comments
All-sky (AIS)
40,000
4
0.1
20.5
7
1
0.1
Galactic caps first
Medium Imaging (MIS)
1000
2
1.5
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6.5
~1
0.6
SDSS, 2dF overlap
Deep Imaging (DIS)
80
4
30
25
7
1.0
0.85
Fields
Ultra-Deep Image (UDIS)
1
0.2
200
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5.5
0.05
0.9
Fields
Nearby Galaxy (NGS)
300
0.5
0.5
27.5 m per
sq. deg.
2.5
---
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Galaxy List
Wide Spectroscopic (WSS)
80
4
30
20
4.5
0.03
0.15
Same fields as DIS
Medium Spectroscopic
(MSS)
8
2
300
21-23
4.5
0.04
0.5
Centers of WSS
Deep Spectroscopic (DSS)
2
4
2000
22.5-24
4.5
0.05
0.9
Fields
Guest Investigator Cycle 1
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4
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GALEX-technical
Pegasus launch
•Uses dichroic
beamsplitter
•Two crossed-delay
line MCP detectors
(2kx2k)
•Insertable grism
for low-resolution
spectra
•Pegasus launch to
LEO
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TAUVEX: performance (GSAT-4)
(better than GALEX!)
O
B
• Assume best case=no stray
light
• Performance (S/N=5) with
SF-2 for stars of different
spectral types
• Lines for monochromatic mag.
17, 18, 19, 20, 21 star
A
G
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