Transcript An introduce of the spectrograph of the GALEX

20110414 Ryu Jinhyuk
GALEX, THE ULTRAVIOLET
SPACE TELESCOPE
Contents
 Introduction
 Why do we want to observe UV wavelength?
 Previous UV missions
 About GALEX
 Instruments
 Schematic view
 Detector
 Grism
 Surveys
 Baseline surveys
 Legacy surveys
 The fate of GALEX
 Sciences done by GALEX
Ultraviolet astronomy
 Temperatures between 104 – 105 K
 HOT stars (young and old)
 Many high excitation lines and resonance lines are
observed in UV
 Ex) Ly α 1215; C IV 1550; C III] 1909
(ref: http://www.astro.virginia.edu/class/whittle/astr553/Topic15/Lecture_15.html, Mark Whittle, Virginia)
Previous UV missions
(ref : http://astronomy.ua.edu/keel/techniques/spacetbl.html, William Keel, Alabama)

OAO-4 (Copernicus)


Astronomical Netherlands Satellite (ANS)



1992. multiband all-sky survey, deep ecliptic survey. Spectroscopy possible.
Operated a program of pointed observations following sky survey, through
January 2001.
Far-Ultraviolet Spectroscopic Explorer (FUSE)


1990 and 1995.
Extreme Ultraviolet Explorer (EUVE)



NASA-ESA-UK. 1978. 45-cm. spectrometers (1200 - 2000, 2000 - 3200 Å). 18-year
lifetime.
Winds from hot stars, coronae of cool stars, hot stars in cold galaxies, variability
mapping of AGN emission regions.
Astro 1 and 2: UV Intensified Telescope (UIT), Hopkins UV Telescope
(HUT), Wisconsin UV Photo Polarimetry Experiment (WUPPE).


1974. 22-cm, photometry (1550 - 3300 Å).
International Ultraviolet Explorer (IUE)


1972 – 1981. 80-cm. Grating spectrometer with photomultiplier.
1999 – 2007. High-resolution spectroscopy from 912 - 1150 Å.
Astron

1983 – 1989. Soviet-French UV spectrometer. Very high orbit (2000 X 200,000 km).
GALEX?
 GALaxy Evolution eXplorer
 All-sky UV imaging and objective-grating
survey since 2003
 Tracing the cosmic history of star formation
at modest redshifts
 Led by CalTech

Yonsei University is supporting science calibration and testing and
supports science operations and science analysis.
 The first mission was planned as a 29-month
mission.
Instruments
 50cm Ritchey-Chretien telescope
 Primary & secondary mirrors are hyperbolic
 Grism
 Dichroic beam splitter
 Two Multi Anode Microchannel Array (MAMA)
detectors
Instruments
 Dichroic beam splitter
 Mean reflectance of 61% over the 1400-1700Å
 Mean transmittance of 83% over the 1800-2750Å
 Blue-edge filter coated on MgF2
 10% rejection of the OI 1304 airglow line
 Red-blocking filter on the NUV folding mirror
 An edge at 2800Å yields an additional factor of 10-20%
rejection of the NUV zodiacal light background.
Multi Anode Microchannel Array
Grism
NUV
FUV
 CaF2, 75/mm
Using spectral order
1
2
 Wedge angle
Spectral resolution
~20Å
~8Å
Corresponding R
~100
~200
 1º.37
 Blaze angle
 2º.33
Mission Surveys
 5 baseline surveys
 Complete in 2007
Survey
Exposure
Time
Sky Coverage
(deg2)
Depth
(mAB)
GR2/3
tiles
GR4 tiles
All-sky Imaging (AIS)
100
26000
20.5
15721
28000**
Medium Imaging (MIS)
1500
1000
23.5
1017
1615
Deep Imaging (DIS)
30000
80
25.0
165
193
Nearby Galaxy Survey
(NGS)
1500
300
28*
296
433
Medium Spectroscopic
(MSS)
150000
5
22
3
5**
*surface density (mag/sq arcsec) **projected
All-sky Imaging Survey (AIS)
Survey
All-sky Imaging (AIS)
Exposure
Time
Sky Coverage
(deg2)
Depth
(mAB)
GR2/3
tiles
GR4 tiles
100
26000
20.5
15721
28000**
 12 positions in one orbit
 |b| < 20º regions are partially covered
 28269 individual pointing's (GR 4/5)
Medium Imaging Survey (MIS)
Survey
Exposure
Time
Sky Coverage
(deg2)
Depth
(mAB)
GR2/3
tiles
GR4 tiles
Medium Imaging (MIS)
1500
1000
23.5
1017
1615
 This survey covers the SDSS spectroscopic
footprint.
 The MIS has been
extended to cover the
2dFGRS and
the WiggleZ project.
Deep Imaging Survey (DIS)
Medium Spectroscopic Survey(MSS)
Survey
Exposure
Time
Sky Coverage
(deg2)
Depth
(mAB)
GR2/3
tiles
GR4 tiles
Deep Imaging (DIS)
30000
80
25.0
165
193
Medium Spectroscopic
(MSS)
150000
5
22
3
5**
 Targets are chosen to have extensive
corollary data from other surveys.
 Ex) COSMOS, DEEP, ELAIS, CDFS, etc.
 Covering 5 square degrees of fields observed
as a part of the DIS.
Nearby Galaxy Survey (NGS)
Survey
Exposure
Time
Sky Coverage
(deg2)
Depth
(mAB)
GR2/3
tiles
GR4 tiles
Nearby Galaxy Survey
(NGS)
1500
300
28*
296
433
 The core of NGS targets the 71 galaxies
included in the SINGS.
Legacy Surveys
Survey
Exposure
Time
Sky coverage
(deg2)
Galactic Cap Survey
SDSS Galactic cap
footprint
1500
20000
Legacy Deep Survey
PS-1, M31, SDSS
30000
100
Milky Way Survey
SEGUE
1500
5000
Legacy Spectroscopy
Project
SDSS
150000
20
Deep Galaxy Survey
Nearby Galaxies
15000
100
300000
7
Ultra Deep imaging
Survey
Current status
 At 4/9/2010, NASA's Jet Propulsion Laboratory
announced that the FUV detector shorted out.
 Despite of that, the GALEX still moves on with
the NUV detector.
 Current data release version is the GR6. There
are no plans for a GR7.
 However, plans for a final processing of all products
and construction of catalogs are under active
discussion.
The fate of GALEX
 Originally, the first mission was planned as a 29month mission, but NASA recommended to
extend the lifetime.
 Legacy surveys and Guest Investigator programs (2005
– 2010, 6 cycles) begun at that time.
 Based on the 2010 Panel's recommendations
NASA has announced that observations will be
terminated on September 30, 2012.
 NASA intends to fund all previously approved
programs (excluding those canceled because
they could not be done without the FUV
detector).
The last mission?
 Observing the available sky to "MIS depth"
(mAB ~ 22.5, ~1500 sec exposure), or 1-orbit
exposures.
 About 16,000 deg2 are not yet imaged but
can be observed safely by GALEX.
 Only NUV detector is available now.
Publications using GALEX
Status of papers (~Feb 2008)
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








Instrument – 7
Report / Review – 12
ISM – 12
Galaxy – 169
Cosmology – 14
Star – 24
Star clusters – 9
GRB – 4
Catalog / Survey – 16
Misc - 5
TOTAL - 272
Top 5 citation
 Martin et al. 2005, ApJ, The Galaxy Evolution Explorer: A
Space Ultraviolet Survey Mission (460)
 We give an overview of the Galaxy Evolution Explorer (GALEX),
(...) GALEX is performing the first space UV sky survey, including
imaging and grism surveys in two bands (1350-1750 and 1750-2750
Å). The surveys include an all-sky imaging survey (mAB~=20.5), a
medium imaging survey of 1000 deg2 (mAB~=23), a deep imaging
survey of 100 deg2 (mAB~=25), and a nearby galaxy survey.
Spectroscopic (slitless) grism surveys (R=100-200) are underway
with various depths and sky coverage. (...) We will use the
measured UV properties of local galaxies, along with corollary
observations, to calibrate the relationship of the UV and global
star formation rate in local galaxies. We will apply this calibration
to distant galaxies discovered in the deep imaging and
spectroscopic surveys to map the history of star formation in the
universe over the redshift range 0<z<2 and probe the physical
drivers of star formation in galaxies. The GALEX mission includes
a guest investigator program, supporting the wide variety of
programs made possible by the first UV sky survey.
Top 5 citation
 Hopkins & Beacom, 2006, ApJ, On the Normalization of the
Cosmic Star Formation History (433)

(...) The data show a compellingly consistent picture of the SFH out to
redshift z~6, with especially tight constraints for z<~1. We fit these data
with simple analytical forms and derive conservative uncertainties. Since
the z<~1 SFH data are quite precise, we investigate the sequence of
assumptions and corrections that together affect the SFH normalization
to test their accuracy, both in this redshift range and beyond. As lower
limits on this normalization, we consider the evolution in stellar and
metal mass densities, and supernova rate density, finding it unlikely that
the SFH normalization is much lower than indicated by our direct fit. As a
corresponding upper limit on the SFH normalization, we consider the
Super-Kamiokande limit on the electron antineutrino (νe) flux from past
core-collapse supernovae, which applies primarily to z<~1. (...) The
traditional Salpeter IMF, assumed for convenience by many authors, is
known to be a poor representation at low stellar masses (<~1 Msolar), and
we show that recently favored IMFs are also constrained. (...) To resolve
the outstanding issues, improved data are called for on the supernova
rate density evolution, the ranges of stellar masses leading to corecollapse and type Ia supernovae, and the antineutrino and neutrino
backgrounds from core-collapse supernovae.
Top 5 citation
 Le Floc'h et al. 2005, ApJ, Infrared Luminosity Functions from the
Chandra Deep Field-South: The Spitzer View on the History of Dusty
Star Formation at 0 <~ z <~ 1 (405)

We analyze a sample of ~2600 Spitzer MIPS 24 μm sources brighter than
~80 μJy and located in the Chandra Deep Field-South to characterize the
evolution of the comoving infrared (IR) energy density of the universe up
to z~1. (...) We then determine an estimate of their total IR luminosities
using various libraries of IR spectral energy distributions. We find that the
24 μm population at 0.5<~z<~1 is dominated by ``luminous infrared
galaxies'' (i.e., 1011 Lsolar<=LIR<=1012 Lsolar) (...) we find very strong
evolution of the contribution of the IR-selected population with lookback time. (…) we find considerable degeneracy between strict evolution
in luminosity and a combination of increases in both density and
luminosity [L*IR~(1+z)3.2+0.7-0.2, φ*IR~(1+z)0.7+0.2-0.6]. (...) Our results imply
that the comoving IR energy density of the universe evolves as (1+z)3.9+/0.4 up to z~1 and that galaxies luminous in the infrared (i.e., L >=1011
IR
Lsolar) are responsible for 70%+/-15% of this energy density at z~1. Taking
into account the contribution of the UV luminosity evolving as (1+z)~2.5,
we infer that these IR-luminous sources dominate the star-forming
activity beyond z~0.7. (…)
Top 5 citation
 Faber et al. 2007, ApJ, Galaxy Luminosity Functions to z~1 from
DEEP2 and COMBO-17: Implications for Red Galaxy Formation
(431)

The DEEP2 and COMBO-17 surveys are compared to study luminosity
functions of red and blue galaxies to z~1. (...) After z~1, M*B has dimmed
by 1.2-1.3 mag for all colors of galaxies, φ* for blue galaxies has hardly
changed, and φ* for red galaxies has at least doubled (our formal value is
~0.5 dex). Luminosity density jB has fallen by 0.6 dex for blue galaxies
but has remained nearly constant for red galaxies. These results imply
that the number and total stellar mass of blue galaxies have been
substantially constant since z~1, whereas those of red galaxies (near L*)
have been significantly rising. To explain the new red galaxies, a ``mixed''
scenario is proposed in which star formation in blue cloud galaxies is
quenched, causing them to migrate to the red sequence, where they
merge further in a small number of stellar mergers. (…) The red
sequence therefore likely builds up in different ways at different times
and masses, and the concept of a single process that is ``downsizing'' (or
upsizing) probably does not apply. Our claim in this paper of a rise in the
number of red galaxies applies to galaxies near L*. Accurate counts of
brighter galaxies on the steep part of the Schechter function require
more accurate photometry than is currently available.
Top 5 citation
 Pérez-González et al. 2005, ApJ, Spitzer View on the
Evolution of Star-forming Galaxies from z = 0 to z ~ 3 (288)
 We use a 24 μm-selected sample containing more than 8000
sources to study the evolution of star-forming galaxies in the
redshift range from z=0 to z~3. (...) The derived redshift
distribution of the sources detected by our survey peaks at
around z=0.6-1.0 (the location of the peak being affected by
cosmic variance) and decays monotonically from z~1 to z~3. (...)
The cosmic star formation rate (SFR) density goes as (1+z)4.0+/-0.2
from z=0 to 0.8. From z=0.8 to z~1.2, the SFR density continues
rising with a smaller slope. At 1.2<z<~3, the cosmic SFR density
remains roughly constant. The SFR density is dominated at low
redshift (z<~0.5) by galaxies that are not very luminous in the
infrared (LTIR<1011 Lsolar, where LTIR is the total infrared luminosity,
integrated from 8 to 1000 μm). The contribution from luminous
and ultraluminous infrared galaxies (LTIR>1011 Lsolar) to the total
SFR density increases steadily from z~0 up to z~2.5, forming at
least half of the newly born stars by z~1.5. Ultraluminous infrared
galaxies (LTIR>1012 Lsolar) play a rapidly increasing role for z>~1.3.