Brian SmithCS 491B

June 2006

RecapHow 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 system4.6 billion years

The Milky Way galaxy13 billion years

The Milky Way galaxy200-400 billion stars100,000 ly across

Local supercluster 200 million ly

As far as we can see13 billion ly

Ivy Mike fusion bomb 18 million°F

Sun’s core27 million°FSun’s core27 million°F

The color and spectral type of astar are indicators of its temperature.

Blue = hotRed = cool

ObservationWhat do we see from stars?

What can we determine from their light?

Electromagnetic SpectrumThe 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

BetelgeuseRed supergiantdiameter is twice

Mar’s orbit

RigelBlue supergiant40,000 times asbright as the Sun

0.0001

0.001

0.01

0.1

1

1 10 100

Log [ l ( mm ) ]

Log [ F

n ( J

y ) ] .

SWIRE Star SEDTypical Flat Galaxy SEDs from SWIREStar with S24 excess1 mJy cutoffSWIRE Saturation LimitsSWIRE Sensitivity Limits

Typical SEDs from SWIRE survey

Spatial indexes

2MASSJ H

K

Spitzer4 IRAC bands and MIPS

24

DataWhat 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. Thefields were selected for the best infrared viewing outsidethe Milky Way galaxy.

CatalogsSpitzer 5 band merge ………………….Spitzer 70 micron ……………………………..Spitzer 160 micron ……………………..………2MASS ……………………………………………Guide Star Catalog II ……………….………Hipparcos …………………………………….………..Tycho ……………………………….…………………IRAS Point Sources ………………………………..IRAS Faint Sources ………………………………..SIMBAD ………………………………………………

3,144,18410,035

4,198124,962228,305

4322,467

133430

8,4673,523,613

The largest tables were partitioned into parent andchild tables. This keeps indexes to a manageablesize and improves efficiency by using constraint exclusion during queries.

2MASS Catalog

Parent table, All columns defined here,No records stored in this table

2MASS - Chandra South field onlycreate table catalogs.twomass_chs ( CHECK ( field = 'chs' ) ) INHERITS (catalogs.twomass);

2MASS - ELAIS N1 field only

2MASS - ELAIS N2 field only

2MASS - ELAIS S1 field only

2MASS - Lockman Hole field only2MASS - 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.

InterfaceHow does the web application interact with the backend?

How does the site remember a user’s choices?

What is the general user flow?

The site consists of a large form spread over several steps. The model-view-controller architecture makes this very easyto handle. Each controller handles requests from the previousand next steps allowing the user to back up and make changes.

Index.jspSimple intro, proceed to first

stepFields Controller

fields.jspStep 1: Choose field/spatial

consts

catalogs.jspStep 2: Choose catalogs

Catalogs Controller

Properties Controller properties.jsp

Step 3: Choose properties

Results Controller results.jsp

Final page, give user results file

The user’s choices are stored in a session scope Java bean. It hasvariables and methods to handle the field, spatial constraints, catalogs and properties selected by the user. The contents of thisbean are displayed in the left-hand sidebar on each step.

[the user flow demo]

ResultsWhat 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).

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).

2. MIPS 24 flux ≥ 1 mJy

3. Spitzer sources must match to 2MASS objects w/in 2”

4. in the range: 0.3 < Ks-[24] < 3.0

Search Criteria

0.00001

0.0001

0.001

0.01

0.1

1 10 100

Log [ l ( mm ) ]

Log [ F

n ( J

y ) ]

.

Lockman_tile32_1228

SWIRE Saturation Limits

SWIRE Sensitivity Levels

K1 V Kurucz

One of a handful of debris disk candidatesfound through this search.

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 seven images are:IRAC3.6, IRAC4.5, IRAC5.8IRAC8.0, MIPS24, MIPS70MIPS160

The End