Download High-z Universe – cont`d

WFC3 Science Themes
The WFC3 White Paper highlights a few science projects where one
may expects the contribution of WFC3 to be ground-breaking. We
have considered programs in each of the following themes:
High-z Universe (Sect. 4.2 and 5.1)
Nearby Galaxies (Sect. 6.1)
Resolved Stellar Populations (Sect. 4.1)
Stars and Interstellar Medium (Sect. 6.2)
Solar System (Sect. 5.2 and 6.3)
In the following we will review each of these themes individually and identify the
major science requirements which can be derived from them.
July 25th, 2000
WFC3 Critical Science Review
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WFC3 Unique Science
For each theme we will also indicate the relevant DRM programs
highlighting those which are enabled by WFC3 and would
otherwise be impossible from the ground or with other existing
space observatories.
This uniqueness can be due to either one or a combination of the
following factors:
• wavelength region inaccessible from the ground
• filters unavailable in other space instruments
• high angular resolution combined to a large FOV
• high sensitivity
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe
WFC3 can address a number of questions within the NASA Origins of
Galaxies theme:
 How do galaxies assemble?
 When and how is gas converted into stars?
 When is the Hubble sequence established?
 What are the first luminous objects in the Universe?
It is essential to efficiently identify high redshift galaxies in a range of
redshift as wide as possible. The panchromatic capabilities of WFC3
allow the exploration from redshift z=1 to 12 with the Lyman-break
technique or photometric redshifts.
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe – cont’d
 The most effective method to identify high-z galaxies is the so-called Lyman break
technique which relies on three filters to identify objects with:
 a relatively flat continuum longward of the Lyman a line and
 a strong reduction in flux shortwards of the Lyman break.
 The strong reduction in flux shortwards of the Lyman break is caused by
absorption due to intervening neutral hydrogen.
The Lyman break technique has been
applied extensively in the last five
years and it has proven both efficient
and reliable for finding high redshift
galaxies regardless of whether Lyman
a is present in emission or in
absorption.
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe – cont’d
Both the low and high z ends are unique to WFC3. The redshift interval z = 1-3 is
unexplored because a systematic study requires high sensitivity below 3000 A over a
large FOV.
The figure illustrates a color selection
criterion to isolate low redshift objects
through the Lyman break technique. Plotted
are about 4,000 models including a range of
metallicity, dust content, age, star formation
history as well as intergalactic opacity due to
neutral hydrogen clouds along the line of
sight. Galaxy models identified by red points
have redshift within the specified range. Blue
points represent models with a different
redshift.
Galaxies found within the red box would
have a high probability of being between
redshift z=1.3 and z=2.4
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe – cont’d
Redshifts above z=5 are unexplored because they require high sensitivity in the
near-IR over a large FOV.
The figure illustrates a color selection
criterion to isolate high redshift objects
through the Lyman break technique.
Plotted are about 4,000 models
including a range of metallicity, dust
content, age, star formation history as
well as intergalactic opacity due to
neutral hydrogen clouds along the line
of sight. Different colors correspond to
different redshifts. The dark green box
identifies objects with redshift z>7.4.
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe – cont’d
The sensitivity of the Lyman-break technique to high redshift galaxies is limited
by the depth of the shortest wavelength image, i.e. shortwards of the Lyman
break. The figure below illustrates the limiting magnitudes required to detect the
UV continuum of galaxies with various star formation rates.
Star formation rates and rest frame
fluxes for starburst galaxies at
different redshift. The calculation
requires Lyman break galaxy
candidates to show at least a 1.6
magnitudes jump at the Lyman
break.
The blue line and points represent the
expected performance of WFC3.
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe – cont’d
Summary of requirements (DRM225):
 assembly of galaxies at redshift 1-3
 large field of view
 requires sensitivity at 2000-4000 A
• point source limiting magnitude UAB = 27.5
 search for very high-redshift galaxies
 large field of view
 requires sensitivity in the near-IR
• point source limiting magnitude JAB = 28.5
July 25th, 2000
WFC3 Critical Science Review
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High-z Universe – cont’d
 Identifying the most distant galaxies
DRM218 - Grism survey for faint Compact Em. Line Objects
DRM225 - A WFC3 Study of Faint Galaxies at z=1-12.
DRM233 - Search for High-z Em. Line Objects with the IR grism
 Galaxy Evolution from high-z to the present
DRM102 - Ultra-deep Imaging
DRM208 - Evolution of Distant Cluster Galaxies in restframe UV
DRM210 - Tracing the evolution of Ellipticals: the UV-upturn
DRM222 - An Optical-Near IR Medium deep survey
DRM240 - UV Parallel Survey
Items in purple-red are unique science areas for WFC3
July 25th, 2000
WFC3 Critical Science Review
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Nearby Galaxies
Understanding the Origin of Galaxies requires also understanding
phenomena and processes in the local Universe. Namely:
 How universal are the processes of star formation in galaxies?
 What are the dust and gas properties of star forming galaxies in
the local Universe?
 What are the implications for observations of high-z galaxies?
Gas, dust, and stars of different ages display features at a variety of
ultraviolet, visible and near infrared wavelengths. A complete studies
of the complex environments in galaxies requires a panchromatic
approach.
July 25th, 2000
WFC3 Critical Science Review
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Nearby Galaxies – cont’d
An example of unique WFC3 science is the study of the 2175 A bump of the
extinction curve with narrow band imaging of distant galaxies through the disks
of nearby galaxies (DRM 219).
The shaded area represent the change in the
observed spectrum due to the 2175 A bump
July 25th, 2000
WFC3 Critical Science Review
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Nearby Galaxies – cont’d
Summary of requirements (DRM219 and DRM 232):
 panchromatic dissection of nearby-galaxies
 sensitivity in the UV and in the near-IR
• UV point source limiting magnitude U=27
• flux in IR iron lines = 1.5 x 10-16 erg s-1 cm-2 arcsec-2
([FeII]1.26mm and [FeII]1.64mm)
 high angular resolution
 large field of view
 narrow band filters
July 25th, 2000
WFC3 Critical Science Review
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Nearby Galaxies – cont’d
 Morphology and Evolution of Galaxies
DRM206 - Wide Field UV Imaging of nearby galaxies
DRM211 - UV color gradients in Elliptical Galaxies
DRM223 - The search for low surface brightness objects
 Starbursts and mergers
DRM103 - Multi-wavelength Observations of Merging Galaxies
DRM229 – Nearby starbursts and their connection with high-z gal.
DRM239 – Structure of Starburst Galaxies
 The interstellar medium in other galaxies
DRM219 – The universality of the 2175 A bump
DRM232 – Nature of the diffuse-ionized medium in local SF gal.
July 25th, 2000
WFC3 Critical Science Review
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Nearby Galaxies – cont’d
 Distance
scales
DRM101 - Cepheid Observations in Virgo cluster
DRM104 - Distance estimates from SB Fluctuations
DRM224 - Post-AGB stars in the Virgo Cluster
 Microlensing
DRM204 – Detection of Earth-like planets through microlensing
DRM231 - Pixel microlensing in M87
July 25th, 2000
WFC3 Critical Science Review
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Resolved Stellar Populations
The star formation history of a galaxy is locked into its stellar
population and can be revealed through stellar archeology:
 What is the baryonic content of galaxies?
 How much mass is locked into low mass stars?
 Is the Initial Mass Function universal?
 How old are globular clusters?
 What are the effects of age, abundances, and rotation on stellar
evolution?
One of the techniques to address these issues relies on studying colormagnitude diagrams using UV and near-IR bands.
July 25th, 2000
WFC3 Critical Science Review
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Resolved Stellar Populations – cont’d
The fraction of mass locked into low mass stars and the IMF universality can be
studied by deriving the lower end of the mass function in the galactic bulge
(DRM 227). The large field of view of WFC3 allows one to reduce the effect of
crowding by observing areas with lower densities of stars while still preserving
sufficient statistics.
Color-magnitude diagram of
low mass stars in the galactic
bulge. The NICMOS data
reach stars of mass twice the
hydrogen-burning limit.
NICMOS/CAM2
WFC3 will go 2 magnitudes
deeper thus pushing toward
the hydrogen-burning limit.
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WFC3 Critical Science Review
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Resolved Stellar Populations – cont’d
Summary of requirements (DRM 220 and 227):
 high precision photometry in a crowded field
 sensitivity in the UV and in the near-IR
• UV point source limiting magnitude U = 25 with S/N=20
• IR point source limiting magnitude J = 27
 high angular resolution at both UV and IR wavelengths
 large field of view
 stable PSF
July 25th, 2000
WFC3 Critical Science Review
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Resolved Stellar Populations – cont’d
 Ages and chemical evolution of stars
DRM202 - The Age of the LMC bar
DRM203 - Ages and abundances of M31 open clusters
DRM207 - Direct determination of metallicities in nearby galaxies
DRM228 - Near-IR Imaging of star forming regions in the LMC
 Evolution of globular clusters
DRM105 - Identifying globular cluster stars with proper motions
DRM214 - Ages of globular clusters from WD cooling sequence
DRM220 - Hot stars in globular clusters
DRM226 - Near-IR Lum. Function of G.C. main sequences
 Star formation in the Galactic bulge
DRM227 - The lower main sequence in the Galactic bulge
DRM235 - Star Formation History of the Galactic Center
July 25th, 2000
WFC3 Critical Science Review
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Stars and ISM
The origin of stars and planetary systems is another theme in the
NASA Origins program that can be addressed by WFC3. Namely:
 How does the star formation rate depend on the environmental
conditions?
 Do OB stars trigger or abort the star formation process?
 What is the frequency of brown dwarfs and super-jovian
companions?
 How frequent are the very low-mass stars?
 How do disks evolve and when are they dissipated?
 What is the interplay between accretion, outflows and final
properties (mass, rotation, multiplicity) of a stellar system
July 25th, 2000
WFC3 Critical Science Review
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Stars and ISM – cont’d
• Herbig-Haro objects are collimated mass outflows (jets) removing material
and angular momentum from the accreting protostars and energizing the
interstellar medium.
• The UVIS imaging capabilities of WFC3 allows to study with unparalled
accuracy the physics of the shock processes occurring when they interact
with the interstellar medium (Herbig-Haro objects, bow shocks).
• The IR capabilities of WFC3 will also allow to study ([FeII], Pab lines) the
outflows hidden within the dense molecular clouds, powered by
protostellar objects in an earlier evolutionary phase.
• HST image quality is constant
with time. Coupled with
spectroscopy (radial velocity),
proper motion measurements
allow to reconstruct the real
3-d kinematics of the outflows.
WFC3 extends the time baseline up to the NGST era.
July 25th, 2000
WFC3 Critical Science Review
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Stars and ISM – cont’d
Summary of requirements (DRM201):
 large filter set to study emission lines and high sensitivity
 requires strategically chosen filters
 sensitivity in the UV, visible, and near-IR
• UV extended source flux = 10-16 erg s-1 cm-2 arcsec-2
• visible extended source flux = 10-16 erg s-1 cm-2 arcsec-2
• IR extended source flux = 10-16 erg s-1 cm-2 arcsec-2
July 25th, 2000
WFC3 Critical Science Review
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Stars and ISM – cont’d
 Formation
DRM236 – Searches for Brown Dwarfs in SF regions
DRM237 – Very low mass luminosity function in young clusters
 The disk-planet connection
DRM106 – Search for disks around stars
DRM201 – WFC3 observations of Herbig-Haro objects
 Death and transfiguration
DRM205 – Origin of Elements: Ejecta-dominated SN remnants
DRM212 – Survey of the Crab nebula
DRM216, 217 – Ejecta from Old Stellar Objects
July 25th, 2000
WFC3 Critical Science Review
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Solar System
Studying our own solar system and its evolution is a required step
in addressing the origin of planetary systems and their evolution
as well as understanding whether and how the habilitability of a
planet evolves.
 what is the water cycle on Mars?
 what are the atmospheric cycles of the giant planets?
 what are the properties of the relic remnants of the early
solar system?
July 25th, 2000
WFC3 Critical Science Review
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Solar System – cont’d
Summary of requirements:
 ices of outer planetary satellites
 near-IR sensitivity and suitable filters
 meteorology of the outer planets
 requires UV, visible and near-IR sensitivity
 requires suitable filters never flown on HST
July 25th, 2000
WFC3 Critical Science Review
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Solar System – cont’d
 Planetary atmospheres
DRM215 – Atmospheric structure of the Outer Planets
DRM238 – Mars Surface and Atmospheric studies using WFC3
 Minor planets and comets
DRM230 – Determination of cometary and KBO sizes using WFC3
DRM234 – Determination of Asteroid Size and Surface Composition
July 25th, 2000
WFC3 Critical Science Review
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