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 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 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

Typical SEDs from SWIRE survey Spatial indexes 2MASS J H K Spitzer 4 IRAC bands and MIPS 24

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 …………………. Spitzer 70 micron …………………………….. Spitzer 160 micron ……………………..……… 2MASS …………………………………………… Guide Star Catalog II ……………….……… Hipparcos …………………………………….……….. Tycho ……………………………….………………… IRAS Point Sources ……………………………….. IRAS Faint Sources ……………………………….. SIMBAD ……………………………………………… 3,144,184 10,035 4, , , , ,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 Catalog Parent table, All columns defined here, No records stored in this table 2MASS - Chandra South field only create 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 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?

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. Index.jsp Simple intro, proceed to first step Fields Controller fields.jsp Step 1: Choose field/spatial consts catalogs.jsp Step 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 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).

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 One of a handful of debris disk candidates found 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, IRAC5.8 IRAC8.0, MIPS24, MIPS70 MIPS160

The End