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TAUVEX and AGNs

TAUVEX=TTelAAviv UniversityUVUV ExExplorer

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Outline

• Background• Technical description• Projected performance• Scientific projects (AGNs)• Conclusions

3IUE: all targets

Why UV?

Earth atmosphereopaque to UV

Low sky background!

UV range

Background

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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

• First spectroscopy: Copernicus• Longest duration: IUE• Most expensive: HST (only part is UV)

TD-1 starlight at 156.5 nmin 3° bins (Sujatha et al. 2004)

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Generic UV Targets

• Comets• Hot stars (high-

mass, evolved [WD])

• Galaxies: evolution• Interstellar & Inter-

Galactic matter• AGNs

SMC

Hyakutake

Hale-Bopp 40 deg

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TAUVEX history

1989: chosen as 1st priority by ISA1991: agreement to launch with SRG1994: planned launch date2000: delays with SRG; start search for alternate launch2003: ISA-ISRO agreement2007: planned launch on GSAT-4

SRG=Spectrum Roentgen-Gamma(incarnation I)Prime contractor: El-Op,

Electro-optical Industries

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• 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 unrestrictedaccess to the sky, TAUVEXis mounted on orientableplatform (MDP).

The Indian connection

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Toward Earth

MDP in launch orientation. MDPmotion is up to 180º from the launch position, to -90≤δ≤+90

δ=0º

δ=+90º

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•3x20cm RC telescopes•~One-degree images•Angular resolution ~7”•UV “solar blind” sensitivity•Unblocked area ~266 cm²(3x)•On GSAT-4, sky scans

TAUVEX basicsTechnical description

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TAUVEX: filter setup

Each telescope with 4-position wheelOne position blocked (shutter=CLS)Three positions with filters

Filter arrangementT1: SF1SF1, SF2, BBF, CLST2: SF2, SF3SF3, BBF, CLST3: SF1SF1, NBF3, SF3SF3, CLS

Includes geometric shadowing, 2 mirrors, lenses+windows, filter trasmission & detector QE

CaF_2cutoff

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Simulated image

Drift rate:“Pixel”=3 arcsecMax. “no-smear” time=1/8 sec

Basic timescale for data frame

Object in FOV: 224 sec along detector diameter at δ=0 (basic exposure time)

High declination advantage!(above 81º, more than 1500 sec per pass)

sec/cos15 ''

TAUVEX performance(and constrains)

Projected performance

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Confusing magnitudes…

21.01(NUV) 22.8

ticmonochroma 19.70(FUV) 22.6limit 1 MIS

19.01(NUV) 20.8

ticmonochroma 17.10(FUV) 20.0limit 1 AIS

Angstromcms erg][

40.2log5log5.2

:

175.21log5.2

:atic)(monochrom

1-2-1-

f

fAB

GALEX

fm

TAUVEX

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TAUVEX vs. HST

•144x more collecting area than TAUVEX•70-700x better resolution•400x smaller FOV (STIS)•200-400x higher cost

Only operating UV instruments at present are ACS & WFPC-2!

HST has:

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GALEX

•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•GALEX operates only 1/3 of the orbit

AIS like TAUVEX singlepass (AB mag limit=18 mono)

GALEX NUV=TAUVEX BBF

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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=SunSun

• 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

SF-2

SF-3

BBF-worstcase

BBF-bestcase

To Sun

Equal-area projection of celestial hemisphere

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GALEX vs. TAUVEX• GALEX: DIS=80 sq.

degrees (~70 fields).

• Limiting AB=25 (1σ); only small part done yet

• 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

To surpass GALEX DIS, TAUVEX requires 10 scans of the Polar Cap area! This is 1-2 months of observations.

GALEX DIS field: Groth region,14ksec exposure

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TAUVEX science: AGNs

• Detection (star-AGN photometric separation)

• Rough redshift determination (UV dropouts)

• Variability studies

Composite AGN spectrum (Telfer et al. 2002, ApJ 565, 773)

Projected results

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How many low-z AGNs?

LIMMAG

20.0019.5019.0018.5018.0017.5017.0016.5016.00.

30

20

10

0

BB

SF1

SF3

AGNs per square degree, with z<1, to different limiting magnitudes.

Conclusion:

TAUVEX will find significant numbers of low-z AGNs

N

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Red≡stars, green≡galaxies, light blue≡AGNs.+reddening GALEX+SDSS (Bianchi et al 2004)

GALEX AGNs: UV vs. optical colors

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Colors vs. redshift

-1.5

-1

-0.5

0

0.5

1

1 2 3 4 5 6 7 8 9 10

10*z

Colo

r (m

ag)

SF1-SF2

SF2-SF3

U-B

B-V

V-R

TAUVEX: UV+optical colors

Color-color plot

-0.5

-0.4

-0.3

-0.2

-0.1

0

-1-0.500.5

SF1-SF2

SF2

-SF

3z

Nearby AGNs (z<1)

UV-UV

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UV-Optical

-0.1

0

0.1

0.2

0.3

0.4

0.5

-1-0.500.5

SF1-SF2

V-R

z

UV-Optical

0

0.2

0.4

0.6

0.8

-0.6-0.4-0.20

SF2-SF3

B-V

z

TAUVEX: UV+optical colors

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Color-color

-0.6

-0.4

-0.2

0

0.2

0.4

-2-101

SF1-SF2

SF2

-SF

3

z

AGNs@.5<z<4, including Ly limit and Ly forest

Importance of simultaneous UV & optical measurements!Importance of simultaneous UV & optical measurements!

AGN colors

-2

-1

0

1

2

3

1 2 3 4 5 6 7 8

z/0.5

Colo

r

SF1-SF2

SF2-SF3

U-B

B-V

V-R

UV-UV

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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

Wedge (A)Strip (B)

Zig-zag )C(

Detection=(x, y, t)

window

CaF2

(Approx. 700“pixels” acrossFOV)

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TD-1A & IUE

All-sky photometric surveyto 9 mag

Targeted mission: spectroscopy

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TAUVEX science: stars & ISM

B star UV spectrum

Use SF2 and NBF3to measure the EWof the ISM band

TD-1PAHs distribution?

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TAUVEX science: galaxies

UV light understandphysics of star-forming processes, extinction

Late-type galaxies=good targets

GALEX 1300 sec image

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Antennae galaxies (NGC4039/4039):importance of the UV sensitivity to establish the nature of stellar populations and determine the full IMF

TAUVEX science: galaxies II

HαLyman cont`.

FUV, NUVHot stars (O,B,A)

Optical (UBVRI)Stars (F,G,K,M)

Near-IRStars (K, M)

Almoznino & Brosch 1998

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TAUVEX science: galaxies III

UV observations track the history of star formation in the last billion years

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TAUVEX science:UV-dropouts (cosmology)

Select z=1-2 galaxiesfrom UV dropouts

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Real image: distortion pattern“Flat-field” (collimator)

TAUVEX: lab performanceNext

More? More?

Edgedischarge

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SURVEYArea [deg]

Length [Month]

Expos [ksec]

m limlog #Gals

Volume<z>Comments

All-sky (AIS)40,00040.120.5710.1Galactic caps first

Medium Imaging (MIS)100021.5236.5~10.6SDSS, 2dF overlap

Deep Imaging (DIS)804302571.00.85Fields

Ultra-Deep Image (UDIS)10.2200265.50.050.9Fields

Nearby Galaxy (NGS) 3000.50.527.5 m per sq. deg.

2.5------Galaxy List

Wide Spectroscopic (WSS) 80430204.50.030.15Same fields as DIS

Medium Spectroscopic (MSS)

8230021-234.50.040.5Centers of WSS

Deep Spectroscopic (DSS)24200022.5-244.50.050.9Fields

Guest Investigator Cycle 1---4--------------- 

         

GALEX surveys

(AB)

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GALEX-technical

•Uses dichroic beamsplitter•Two crossed-delay line MCP detectors (2kx2k)•Insertable grism for low-resolution spectra•Pegasus launch to LEO

Pegasus launch

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• 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

OO

BB AA GG

(better than GALEX!)

TAUVEX: performance (GSAT-4)