Lecture 6 Summary and Perspectives

Lecture 6 Summary and Perspectives
Matthew Hayes Stockholm University, department of astronomy Oskar Klein Centre for Cosmoparticle Physics

Lecture 6 Overview 6.1. Putting it all together: how does Ly-alpha escape galaxies 6.2. Is there an evolutionary sequence? 6.3. What we need to know next

The local universe is the only place you can put all this together
Quantity soup Stellar mass, stellar age, compactness, Ha EW, colour, dust content, metallicity, ionizing field, HI mass, outflow velocity, HI covering fraction, HI column density, halo size, turbulent/ordered velocity The local universe is the only place you can put all this together Lyman alpha regulation in galaxies is a multi-parametric problem with a wide variety of possible outcomes

Warning: Exercises Stellar mass, stellar age, compactness, Ha EW, colour, dust content, metallicity, ionizing field, HI mass, outflow velocity, HI covering fraction, HI column density, halo size, turbulent/ordered velocity Sort into those that characterize A. the scattering medium and B. the intrinsic production How can we reduce this list into something more manageable? Keep in mind throughout the difference between effects that ease transfer/enhance Lya and those that relate to Lya production

Evolutionary sequence of a cluster
Tenorio-Tagle+1999, based upon hydro simulations of Silich+1998 Star formation episode starts Lya produced, but gas is static – no Lya emission O Star winds and first supernovae – feedback, and winds turn on Outflow – Lya emitted. Asymmetric PCygni- like line Run out of ionizing stars. Lya turns off CLUSTER MODEL IS SIMPLE STELLAR POPULATION (SSP): all stars form at the same time, and all have the same age = ‘Instantaneous burst’.

Ionizing budget vs time for SSP
Key moments on the timeline: 0 Myr: star-formation starts Ionizing budget high Winds from O stars only 3 Myr: first supernovae Ionizing budget down by 0.5 dex SNe explode + O stars winds 8 Myr: last ionizing stars explode No more ionizing stars Winds from SNe only 30 Myr: last SNe explode No more mechanical energy Leitherer+1999 Ionizing photons produced only over ~8 Myr. Bulk of the mechanical feedback from SNe comes afterwards. Wasted in the SSP approximation.

Galaxy superwind cartoons
‘Blowout’ phase Heckman+1990 ‘Snowplough’ phase Starburst  Many SN explosions  ejecta thermalize  shock heat  expand  sweeps up material  multi-phase superwind SN blow out winds, orientation effects, RT instabilities

Galaxies are not spherically symmetric or SSPs
Generalized the star cluster scenario to disk galaxies Mas Hesse+2003 Observed spectral line profiles represent different phases along this sequence.

Galaxies are not spherically symmetric or SSPs
Generalized the star cluster scenario to disk galaxies Mas Hesse+2003 Kunth et al 1998 Dwarf galaxies so young that they have not yet driven outflows?

Putting it all together

Terrible fit in the red wing, BTW

Terrible fit in the red wing, BTW OK, no – it tells us something is missing from the model

Part 1: A little game about identifying spectral regions in quasar spectra

Part 1: A little game about identifying spectral regions in quasar spectra 

Part 1: The first person to shout the wavelength region in the full spectrum wins a prize

Part 1: The first person to shout the wavelength region in the full spectrum wins a prize 3…

Part 1: The first person to shout the wavelength region in the full spectrum wins a prize

Part 1: The first person to shout the wavelength region in the full spectrum wins a prize 

GO! GO! GO!

Part 2: Identify the object?

Part 2: Identify the object? 3C 273

Part 3: Which telescope first observed the Lya spectrum of 3C 273? Part 2: Identify the object? 3C 273

Part 3: Which telescope first observed the Lya spectrum of 3C 273? HINT! Part 2: Identify the object? 3C 273

Part 3: Which telescope first observed the Lya spectrum of 3C 273? HINT! FOT ! Part 2: Identify the object? 3C 273

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies And the dwarf starbursts (e.g. I Zw 18) do not

Two questions What makes the escape fraction high? What properties govern the escape in astrophysical environments? What makes a Lya emitter?

Two questions What makes the escape fraction high? What properties govern the escape in astrophysical environments? Properties of the ‘transfer medium’: dust abundance + distribution, HI kinematics + geometry … What makes a Lya emitter? Intrinsic Lya properties: stellar evolutionary phase, star-forming environment, metallicity, rotation…? combined with Properties of the ‘transfer medium’: dust abundance + distribution, HI kinematics + geometry …

And then you can make stuff up
Initial mass function Number of X-ray binaries Accreting stellar binaries Composition of dust …

TASK Lyman alpha emitting galaxies are/have: lower stellar mass
Divide these into intrinsic quantities that relate to production and escape Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies Mass-metallicity relation

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies Scattering related

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies Dust related

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies Evolution related

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies Feedback related

Lyman alpha emitting galaxies are/have: lower stellar mass younger more compact higher Ha EW bluer less dusty lower metallicity more strongly ionizing lower in HI mass faster outflows lower HI covering fractions lower HI column densities larger halos more turbulent velocity fields than non Lya emitting galaxies Mass-metallicity relation Evolution related Scattering related Dust related Feedback related

Stellar mass, stellar age, compactness, Ha EW, colour, dust content, metallicity, ionizing field, HI mass, outflow velocity, HI covering fraction, HI column density, halo size, turbulent/ordered velocity DM halo mass drives stellar mass Halo mass drives gas mass, and makes stars Star formation produces dust, metals, and supernovae Supernovae drive outflows, disrupt + fragment the ISM, reduce the covering fraction  channels of lower column density Evolutionary scenario should emerge I do not claim this is correct – if it were this easy it would be done Proper statistical analyses needed to make these more manageable. E.g. fundamental plane, or fundamental metallicity relation.

Group work What more observations do you want?
Saying 108 galaxies is not an acceptable answer

What more we want to know?
True atomic gas distribution on ISM scales: Wait for the SKA Bring the Lya samples very much closer How is the spectral Lya profile built as a function of {x,y}? Can we predict the Lya observable properties? Statistical tests to reduce the parameter space in the previous lists. Fully exploit the samples, and ‘homogenize’ the datasets.

Thank you! Anne, Myriam, Pierre, Sebastiano, and Hakim!
Mark, X(avier), and Masami! Everyone who came, asked questions, talked, contributed, …

Lecture 6 Summary and Perspectives

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