Transcript 13 billion years

Brian Smith
CS 491B
June 2006
Recap
How big are stars?
How old are they?
How far away are other stars and galaxies?
How hot are they and how does this affect their color?
Earth is the largest of the inner planets…
Earth: 8,000 miles
…but is dwarfed by the gas giants…
Jupiter: 89,000 miles
…and none can compare to our star, the Sun.
870,000 miles
Earliest fossils (cyanobacteria)
3.5 billion years
Our solar system
4.6 billion years
The Milky Way galaxy
13 billion years
The Milky Way galaxy
200-400 billion stars
100,000 ly across
Local supercluster
200 million ly
As far as we can see
13 billion ly
Ivy Mike fusion bomb
18 million°F
Sun’s core
27 million°F
The color and
spectral type of a
star are indicators
of its temperature.
Blue = hot
Red = cool
Observation
What do we see from stars?
What can we determine from their light?
Electromagnetic Spectrum
The full spectrum of radiation in our universe is
very broad compared to the light we can observe
with our eyes. Stars emit energy throughout this
range but at some wavelengths more than others.
Blackbody radiation curve
Betelgeuse
Red supergiant
diameter is twice
Mar’s orbit
Rigel
Blue supergiant
40,000 times as
bright as the Sun
1
.
Spitzer
4 IRAC bands and MIPS 24
Log [ Fn ( Jy ) ]
0.1
2MASS
J H K
Typical SEDs
from SWIRE survey
0.01
Spatial
indexes
0.001
SWIRE Star SED
Typical Flat Galaxy SEDs fro m SWIRE
Star with S24 excess
1mJy cuto ff
SWIRE Saturatio n Limits
SWIRE Sensitivity Limits
0.0001
1
10
Log [ l ( mm ) ]
100
Data
What parts of the sky did we cover?
What astronomical catalogs are available?
How are the catalogs matched?
The six fields of the SWIRE survey covering about fifty
square degrees of the sky at high galactic latitudes. The
fields were selected for the best infrared viewing outside
the Milky Way galaxy.
Catalogs
Spitzer 5 band merge …………………. 3,144,184
Spitzer 70 micron …………………………….. 10,035
Spitzer 160 micron ……………………..……… 4,198
2MASS …………………………………………… 124,962
Guide Star Catalog II ……………….……… 228,305
Hipparcos …………………………………….……….. 432
Tycho ……………………………….………………… 2,467
IRAS Point Sources ……………………………….. 133
IRAS Faint Sources ……………………………….. 430
SIMBAD ……………………………………………… 8,467
3,523,613
The largest tables were partitioned into parent and
child tables. This keeps indexes to a manageable
size and improves efficiency by using constraint
exclusion during queries.
2MASS - Chandra South field only
2MASS Catalog
create table catalogs.twomass_chs (
CHECK ( field = 'chs' ) ) INHERITS
(catalogs.twomass);
Parent table,
All columns defined here,
No records stored in this table
2MASS - ELAIS N1 field only
2MASS - ELAIS N2 field only
2MASS - ELAIS S1 field only
2MASS - Lockman Hole field only
2MASS - XMM-LSS field only
The objects were matched based on their positions
in the sky. Objects within a specified distance can be
considered the same object. This matching was
made possible by PostgreSQL’s geometric data types
and functions and its spatial indexes.
Interface
How does the web application interact with the backend?
How does the site remember a user’s choices?
What is the general user flow?
Index.jsp
Simple intro, proceed to first step
Fields Controller
fields.jsp
Step 1: Choose field/spatial consts
Catalogs Controller
catalogs.jsp
Step 2: Choose catalogs
Properties Controller
properties.jsp
Step 3: Choose properties
Results Controller
results.jsp
Final page, give user results file
The site consists of a large form spread over several steps.
The model-view-controller architecture makes this very easy
to handle. Each controller handles requests from the previous
and next steps allowing the user to back up and make changes.
The user’s choices are stored in a session scope Java bean. It has
variables and methods to handle the field, spatial constraints,
catalogs and properties selected by the user. The contents of this
bean are displayed in the left-hand sidebar on each step.
[the user flow demo]
Results
What are you going to do with all that junk?
When a star is newly formed
it is surrounded by a flat
sheet of gas and dust called
a debris disk.
Searching for Debris Disks
The goal of the program is to search for
stars that have an excess in the long
infrared wavelengths to find debris disks.
Over 15% of nearby main sequence stars
have infrared excesses.
The Spitzer Space Telescope has
unprecedented sensitivity allowing us to
detect debris disks at hundreds or even
thousands of parsecs, and it did an
unbiased survey (meaning no selection
based on star characteristics).
Search Criteria
2. MIPS 24 flux ≥ 1 mJy
3. Spitzer sources must
match to 2MASS
objects w/in 2”
.
0.01
Log [ Fn ( Jy ) ]
1. Sources with non-null
flux values in all first
five Spitzer bands
(IRAC 3.6, 4.5, 5.8,
8.0 mm, and MIPS
24 mm).
0.1
0.001
Lockman_tile32_1228
SWIRE Saturation Limits
SWIRE Sensitivity Levels
0.0001
K1 V Kurucz
0.00001
4. in the range:
0.3 < Ks-[24] < 3.0
1
10
100
Log [ l ( mm ) ]
One of a handful of debris disk candidates
found through this search.
The seven images are:
IRAC3.6, IRAC4.5, IRAC5.8
IRAC8.0, MIPS24, MIPS70
MIPS160
Once candidates were found the Spitzer
astonomers examined the original
images for confirmation. Some were
unreliable but several proved to be valid
discoveries, like this one in the Lockman
Hole field. Note the absence of the other
stars in the MIPS images while the
candidate still has a strong infrared flux.
The End