Seeing Stars with Radio Eyes

Christopher G. De PreeRARE CATSGreen Bank, WVJune 2002

Overview

Why study star formation? Some unanswered questions in star

formation Successes and limitations of optical

wavelength studies Advantages of radio wavelength

studies Recent discoveries in star formation Conclusions

Why study Star Formation? We are made of star stuff

Nucleosynthesis creates elements through iron (Fe)

Supernovae create everything else The death and birth of stars may

be linked (triggered star formation) Complex molecules can form on

dust grains near young stars Young stars “stir up” clouds of gas

Why study Star Formation (cont.)? Stars have a “life process”

Star Formation Stellar Evolution Supernovae, planetary nebulae

Where there are stars, there are planets

Effect on galactic evolution The Antennae (Arp 224) Andromeda HST with CO (BIMA)

Giant Molecular

Clouds in

Andromeda

The Process of Star Formation Collapsing molecular cloud core Inside-out collapse produces a

protostar plus accretion disk Bipolar molecular outflow carries away

angular momentum What do we look for to see the earliest

stages? Dense cloud cores Infalling molecular material Molecular disks/outflows

Jet Example: Core of NGC 2071

Open questions in star formation Do all stars form planets? Are accretion disks common to all

star masses? Do all young stars have outflows?

For how long? Do massive stars (>5 solar mass)

form differently than low mass stars? Do massive star outflows “stir up”

molecular clouds?

Optical wavelength studies Best for studying

Source of ionization (stars) Ionized gas (if unobscured, e.g. Orion)

Potential problems Star forming regions are often highly

obscured (e.g. NGC 253) The early stages of star formation are not

optically visible (radio, infrared) Molecular material (fuel tank) best

detected at radio frequencies Deeply embedded ionized material best

detected at radio frequencies

Radio wavelength studies (star formation) Molecular gas (the fuel tank)

Molecular clouds Protostellar disks Molecular outflows Complex molecules

Molecules and Outflows

Molecules in Orion Distribution of molecules Abundance of molecules Source motions (rotations

and outflows) Presence of complex

molecules Potential for pre-life

chemistry

Viewing the Milky Way Galaxy 90 cm image A different view Young stars Dying stars Magnetic fields Ted LaRosa

(Kennesaw)

My Interests in this Puzzle HII Regions (regions of ionized gas

around massive stars) High resolution imaging of the

ionized gas Kinematics (motions) of the ionized

gas Understanding the earliest stages

of massive star formation

Radio wavelength studies of HII Regions Obscured ionized gas

High density gas (young regions) Gas velocities (ionized outflows)

Ionized shells at the centers of outflows (e.g. G5.89 Observed with the VLA)

Disadvantage: resolution Very Large Array (VLA) Berkeley Illinois Maryland Association Owens Valley Radio Observatory But: VLA at 7 mm—same resolution as

the Hubble Space Telescope

Observing with the Very Large Array

W49 Observed with the VLA(2000)

W49A Star Forming Region at 600 A.U. Resolution (2002)

“Bipolar Outflow”

Spectral Lines/Bohr Model of the Atom

“Imaging Spectroscopy”

Recent Discoveries Optical

Extrasolar planets (Doppler shift) Protoplanetary disks (Orion) Bipolar outflows (HH objects)

Recent Discoveries Radio

Rotating protoplanetary disks Ionized and molecular outflows High density regions Outflows may support clouds

What have we learned?

Some HII regions are much smaller and far brighter than previously thought

“Typical” HII regions were thought to be ~1 pc in diameter

“Typical ultracompact” HII regions that we study are ~0.01 pc in diameter

These new sources are younger and brighter—give us insight into an earlier phase of star formation

Spectral line detections—we see rotation and outflow in many sources

Conclusions Star formation studies tell us

about... Chemical evolution of the universe Structure and evolution of galaxies Enrichment of the space between

the stars (the ISM) Abundance of elements Prevalence of planets

Radio observations reveal... Embedded protostars Rotating molecular disks Molecular outflows Complex organic molecules

Future developments

The Millimeter Array (MMA) 36 10-meter antennas Llano de Chajnantor, Chile Elevatation-16,400 feet

VLA Upgrade (EVLA) Increased resolution New correlator (spectral line &

sensitivity) Fully equipped at 7 mm