The emission line universe galactic sources of emission lines
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The Emission Line Universe: Galactic Sources of Emission Lines. Stephen S. Eikenberry University of Florida 22 November 2006. OUTLINE. Introduction Infrared Emission Lines Nebular Galactic Emission Line Sources Stellar Galactic Emission Line Sources Summary & Future Prospects.

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The emission line universe galactic sources of emission lines

The Emission Line Universe: Galactic Sources of Emission Lines

Stephen S. Eikenberry

University of Florida

22 November 2006


Outline

OUTLINE

  • Introduction

  • Infrared Emission Lines

  • Nebular Galactic Emission Line Sources

  • Stellar Galactic Emission Line Sources

  • Summary & Future Prospects


What are galactic sources

What are “Galactic” Sources?

  • Essentially all emission lines arise from discrete objects within a galaxy  almost all objects discussed in WS XVIII are fundamentally “Galactic”

  • But … others here will cover HII regions, AGN, integrated galaxy spectra, etc.

  • I’ll focus on “other” Galactic sources of emission


What are galactic sources1

What are “Galactic” Sources?


Ii why infrared emission lines

II. Why Infrared Emission Lines?

  • Infrared – why bother?

  • Hydrogen has transitions in the infrared (IR), but UV (Lyman) and optical (Balmer) are stronger

  • Then again … optical – why bother? Lyman >> Balmer …

  • But, the Universe is more transparent to Balmer lines than Lyman lines

  • Even though Lyman is intrinsically brighter, Balmer is often more useful


Ii why infrared emission lines1

II. Why Infrared Emission Lines?

  • The Galaxy is more transparent to IR than optical emission

  • Why? Because most dust grains are smaller than ~1 m

  • Thus, they do not absorb/scatter well at wavelengths  > 1 m

  • For instance, in the K-band (~2.2 m) AK ~ 0.1 AV (magnitudes!)

  • For many Galactic sources, IR is the ONLY waveband


Example the galactic center

Example: The Galactic Center

POSS-B

POSS-R

POSS “IR”


Example the galactic center1

Example: The Galactic Center

2MASS-J

2MASS-H

2MASS-K


Example the galactic center2

Example: The Galactic Center

  • AK ~ 3 mag (~6% transmission)

  • AV ~30 mag (~10-12 transmission!!)

POSS-R

2MASS-K


Ir optical difference detectors

IR/Optical Difference:Detectors

  • CCDs do not function well @  >1.0 m

  • The “bandgap” energy of silicon (~1.0 eV) corresponds to this wavelength (the “bandgap cutoff” of silicon)

  • Instead of silicon, We use other (poorer) semiconductor materials

    • HgCdTe (0.9-2.5 m)

    • InSb (1-5.5 m)

    • Si:As BIB (~5-28 m)


Current ir detectors

Current IR Detectors

  • HgCdTe: Current state-of-the art arrays

    • QE ~70% (1-2.5 m)

    • Read noise ~10 e-

    • 2048x2048-pixel format

  • InSb: Current state-of-the-art arrays

    • QE >90% (1-5.5m)

    • Read noise ~25 e-

    • 2048x2048-pixel format


Ir optical difference cryogenics

IR/Optical Difference: Cryogenics

  • For sensitive observations, we need kT  hc/ (why??)

  • (If not, thermal self-emission of the detector dominates over celestial sources)

  • 1-2.5 m  T < 70-80K (i.e. HgCdTe)

  • 1-5 m  T < 30-40K (i.e. InSb)

  • 5-30 m  T < 4-8K (i.e. Si:As BIB)


Implications of cryogenics

Implications of cryogenics

  • Vacuum systems (for thermal isolation)

  • Large cryostats

  • Cryogenic liquids:

    • LN2 77K

    • LHe  4K

  • Mechanical cryocoolers:

    • Ultra-pure He

    • Compressors

    • “Cold heads”


Ir obs atmospheric ir transmission

IR Obs: Atmospheric IR Transmission


Ir obs atmospheric ir transmission1

IR Obs: Atmospheric IR Transmission


Ir obs atmospheric ir transmission2

IR Obs: Atmospheric IR Transmission


Ir obs atmospheric ir emission

IR Obs: Atmospheric IR Emission


Atmospheric ir emission

Atmospheric IR Emission

  • Dominant source of in-band background


Important ir lines hydrogen

Important IR Lines: Hydrogen

Paschen Series

Brackett Series


Important ir lines hydrogen1

Important IR Lines: Hydrogen

Pfund Series


Ir hydrogen lines trouble

IR Hydrogen Lines: Trouble

Paschen Series

Brackett Series


Ir hydrogen lines trouble1

IR Hydrogen Lines: Trouble

Pfund Series


Ir hydrogen lines implications

IR Hydrogen Lines: Implications

  • None of the “IR” hydrogen series have (ground) observable “” transitions (!)

  • From the ground, we cannot observe the equivalent of the Balmer decrement

  • We can combine Pa/Br (two strongest easily-observable transitions of each series)

    • “IR decrement” of sorts

    • But … these two have no common energy levels

    • Greater physical uncertainty in parameters


Important ir lines molecules

Important IR Lines: Molecules

  • Not many molecular transitions are easily observed in the optical

  • “Hard” optical/UV radiation dissocates them (!)

  • Many molecular transitions observable in the IR from “cool” objects

  • Particularly strong are H2 ro-vibrational transitions (many from 1-3 m; strongest at 2.12 m)

  • Also, CO bandheads at 2.3-2.5 m

    • Mostly seen in absorption in cool giant stars

    • Also seen in emission occasionally (more later)


Iii nebular sources in the galaxy

III. Nebular Sources in the Galaxy

  • Galactic HII Regions

  • Planetary Nebulae

  • Supernova Remnants


Galactic hii regions

Galactic HII Regions

  • These are generally covered elsewhere in the Winter School lectures

  • Important point: hydrogen is dominant (why?)

  • One Milky Way –centric point: while most past work has been done in the optical/UV (even in our Galaxy), IR is still important for current/future work


Galactic hii regions why ir

Galactic HII Regions: Why IR?

Example: Cepheus A

POSS “IR”

POSS-B

2MASS-J


Planetary nebulae why

Planetary Nebulae: Why?

  • PNe are the (near-)final evolutionary phase for most stars in the Universe

  • The PNe phase is responsible for the return of chemically-enriched material to the ISM

  • They exhibit very interesting outflow physics

  • They are PRETTY!


Planetary nebulae why1

Planetary Nebulae: Why?


Planetary nebulae

Planetary Nebulae

  • What can PNe emission lines tell us?

    • Electron density

    • Electron temperature

    • Ionic abundance

    • H2 shows shock vs radiative excitation

    • [FeII] shows shocks

    • Kinematics of Outflows & Morphology


Pne electron density

PNe: Electron Density

  • Key transitions: 4S3/2-2D5/2 and 4S3/2-2D3/2 for [OII] and [SII]

  • Also [ClII] & [ArIV]

  • Why?

From Stanghellini & Kaler


Pne other basics

PNe: Other basics

  • Similar diagnostics for electron temperatures

  • Combine temperatures & densities with models  ionic abundances

  • Major sources of uncertainty for Planetary Nebulae diagnostics:

    • distance

    • internal extinction (throws off line ratios; less so in the IR)


Pne ir spectra

PNe: IR Spectra


Pne h 2 diagnostics

PNe: H2 Diagnostics

  • H2 lines can be excited by both fluorescence and by thermal (collisional/shock) mechanisms

  • At low densities, with UV excitation of cool (T ~100K) material have 2.12/2.25-micron ratio of ~1.7

  • These are 1-0 S(1) and 2-1 S(1) transitions

  • At higher densities (>104 cm-3), this ratio increases and becomes a good probe of temperature (up to ~1000K)


Pne feii diagnostics

PNe: [FeII] Diagnostics

  • Fe usually “depletes” onto dust grains in ISM

  • shocks break up dust  greatly increase Fe abundance in ISM (temporarily)

  • Thus, [FeII] provides excellent shock diagnostic (kinematics, density) for PNe

  • Typically only seen in the fastest-moving PNe shocks


Pne outflows morphology

PNe: Outflows & Morphology

  • Contrary to simple expectations, most PNe seem to be VERY non-spherical (!)

  • Most show very eye-catching aspheric symmetry

  • Strong indications of collimated outflows in some


The emission line universe galactic sources of emission lines

Collimation :

“mild” “high”


The emission line universe galactic sources of emission lines

Point-symmetry is pervasive…


Planetary nebulae1

Planetary Nebulae

Point-symmetry is usually associated with:

  • Bipolarity

    - A progressive variation in the direction of the outflows

  • episodic events of (collimated) mass-loss.

    Thus, point-symmetry indicates the presence of a

    Bipolar, Rotating, Episodic Jet or Collimated Outflow ( BRET).

    A few representative examples next …


The emission line universe galactic sources of emission lines

Point-symmetry  morphology--BRET  kinematicsIn a true BRET morphology is reflected in its kinematics


Possible models for morphologies

Possible Models for Morphologies


The emission line universe galactic sources of emission lines

There is a wide range of speeds in the COFsfrom a few tens to several hundred km/s….

MyCn18, first PN to break the ~500 km/s barrier…now other examples such as He 3-1475 and Mz 3…

However, their masses (~1028-29 g), kinetic energy (~1043-44 ergs) and mechanical power (~1033-34 ergs/s) still are poorly determined in most cases …


The emission line universe galactic sources of emission lines

MHD models with magnetic axis tilted with respect to bipolar wind axis…


The emission line universe galactic sources of emission lines

Mastrodemos & Morris 1999

Binary cores: COFs and axis-symmetry may be produced either by : -Wind accretion from AGB onto WD or MS companion

Wind accretion may produce bipolar COFs that explain plane – symmetry, such as in the case of M2-9 (Soker & Livio 2001)

Soker & Rappaport 2000


The emission line universe galactic sources of emission lines

…or via RLOF after a CE phase where low mass secondary is destroyed during an unstable mass transfer process, forming an accretion disk…

Some expected implications of binary core on COFs

Accretion through RLOF is short-lived at end of AGB .


Morpho kinematics conclusions

Morpho/Kinematics: Conclusions

  • COFs as BRETs (Poly-polar or P-S) are ubiquitous in PNe.

  • COFs develop since the very early stages of formation of the proto-PN.

  • Although their velocities are now well characterized, their masses, kinetic energy and luminosities need better determination to confront ionized, atomic and molecular parameters with stellar power input (radiative, gravitational, etc.)


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