full spectral analysis of galaxies - are we there yet? ben panter, edinburgh [email protected]
TRANSCRIPT
![Page 2: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/2.jpg)
Full Spectral Analysis?Emission lines give information on current star formation, but tell us nothing about the history.Good for redshifts too!
Continuum shape can reveal generics of populations, and perhaps a mass to light ratio.
Spectral features can help reveal the average metallicity when stars formed, and perhaps their mean age
=
+
+
![Page 3: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/3.jpg)
Pixels vs. Parameters
Models
Observations
Comparison Method3000 pixels
Need a clever way to perform this analysis for any non-trivial
parameterisation
![Page 4: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/4.jpg)
How does MOPED solve this?
Short version:• Pick the pixels which tell you most about the parameters you
wish to extract from the data• Create a weighting vector, b, for each parameter which gives
a projection y (scalar) of the dataset x.
• ym=bm.x
• If model is good, then these y numbers encapsulate all the information about the parameters – the compression is lossless
• Can use these y values to determine likelihood of a parameter set, rather than x – hence computation time nparams not npixels
Long version: Heavens et al. 2000, Reichardt et al. 2001, Panter 2005.
Massively Optimized Parameter Estimation and Data Compression
![Page 5: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/5.jpg)
MOPED2 (Mathis 06)
STARLIGHT (Cid Fernandez 05)
BLV (Nolan 06)MOPED (Panter 03)
VEPSA (Tojeiro 07) STECMAP (Ocvirk 03)
Not the only show in town…
![Page 6: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/6.jpg)
So why bother?
z
High redshift sources• Limited to bright galaxies• Subject to IMF (high end)• Dependent on models• Uncertain dust correction
Low redshift sources• Subject to IMF (low end)• Dependence on models• Dust correction easier to manage• Many, many more galaxies...
z
![Page 7: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/7.jpg)
Cosmic SFR to z~2 from z~0.1 sources (DR3)
![Page 8: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/8.jpg)
Downsizing – Not Offset!
![Page 9: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/9.jpg)
DownsizingDownsizing
![Page 10: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/10.jpg)
Build up of Stellar Mass
![Page 11: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/11.jpg)
Metallicity History Maps
Preliminary result, please do not redistribute
![Page 12: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/12.jpg)
So are we there yet?
Lots of results that reassuringly agree with other indicators
Lots of information still to be untangled…
![Page 13: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/13.jpg)
Looking at the modelsMissing Ingredients:• Alpha enhancement
– Models available
• Variable abundances– Infancy
• UV Continuum• IR Continuum
• Need to separate…
Models
Observations
Comparison Method
![Page 14: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/14.jpg)
How can we differentiate features?• Two groups of high signal to noise
galaxies:– Telescope features fixed in observed frame,
Modelling features fixed in rest frame.– Very tight redshift range for clear observed
frame (W)– Wider range of redshift to smooth observed
frame (T)– Subtract residuals of W from T
![Page 15: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/15.jpg)
Where do the models fail?
Average
Tight z
Wide z
T - W
![Page 16: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/16.jpg)
Incorporating Alpha
Panter / Coelho in prep.
Preliminary result, please do not redistribute
![Page 17: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/17.jpg)
How different are the models?
![Page 18: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/18.jpg)
Modelling all the way - UV to IR
Nolan et al. 06
![Page 19: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/19.jpg)
Future Surveys – what is needed?
Models
Observations
Comparison Method
• S/N in sloan is good, but other problems appear to dominate– Spectrophotometry
• Redshift range– Moderately higher
redshift helps a lot
• Database methods essential– GAVO
![Page 20: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/20.jpg)
2SLAQ/DEEP2/GDDS/GOODS...
Higher redshift allows us to probe early epoch populations
High z SF from mid-z sources
Present data does not support reliable analysis (?)
![Page 21: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/21.jpg)
Wish list for higher z FSA
• Resolution of ~ 1A• UV + Visible + IR with overlap• SDSS or better S/N • 10,000 galaxy spectra• z ~ 1• Accurate calibration of
spectrophotometry– Better than sloan?
![Page 22: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/22.jpg)
Conclusions• Methods are in
place and tested• Models need
– Wider range at high res (observations!)
/ Var. Abundances– Uniform format
• Data needed– Moderately higher z– Spectrophotometry
(more important than numbers?)
Models
Observations
Comparison Method
![Page 23: Full Spectral Analysis of Galaxies - Are we there yet? Ben Panter, Edinburgh bdp@roe.ac.uk](https://reader035.vdocument.in/reader035/viewer/2022062423/56649ec55503460f94bcfaa9/html5/thumbnails/23.jpg)