14 Sep 2006NVO Summer School 2006 1

THE US NATIONAL VIRTUAL OBSERVATORY

Shape of Galaxy Rotation Curves A multiwavelength study using the VO

Barbara Catinella, Arecibo Obs.Luca Cortese, Cardiff Univ.

Chris Springob, Naval Research Lab.

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Rotation Curves (RCs)

pepe0pe rrα1 rr- exp1 V(r)V

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SFI++ RC sample

• SFI++ I-band photometry+ Hi/H spectroscopy sample, collected by Cornell Univ. ExtraGalactic Group (EGG) to study the peculiar velocity field in the local universe using the Tully-Fisher relation (TFR)

• Largest sample of RCs to date (N~3000)

Red: early type galaxies (≤ Sb )Blue: late type galaxies (≥ Sbc)

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Our Project

• Make the RC dataset available through the VO– Convert the RC files into VOTable format– Make a MySQL database– Make a web interface to access and query the data

• Cross-match our dataset with others available through the NVO

• Study the dependence of RC parameters on galaxy properties at different wavelengths

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Making the data available to the VO

• Made VOTables using VOConvert

• MySQL database

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Web interface (HTML/PHP)

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Cross-match with other datasets using the VO

• Springob et al. 2005 HI archive -> VO (B. Kent)• SDSS DR5 -> SDSS website• 2MASS XSC -> OpenSkyQuery

Used topcat to x-match datasets and look for correlations between RC parameters and photometric quantities

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Results: TFR in K band

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Results: TFR at different ’s

TFR is steeper at redder ’s

• holds true for both SDSS and 2MASS

• consistent with results from the literature (Sakai et al. 2000; Pizagno et al. 2006)

• Dependence is consistent with expectations, as dimmer galaxies tend to be bluer, which means shallower slope at blue ’s

• Scatter is relatively independent of waveband for 2MASS, but increases for bluer bands in SDSS. In contrast, Pizagno et al. 2006 says SDSS TF scatter is independent of waveband

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Results: SB’s vs. RC widths

• Brighter galaxies have larger widths, as expected

• Scatter in the SB relations is larger than in the L relations

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Results: SB’s vs. RC widths

• Brighter galaxies have larger widths, as expected

• Scatter in the SB relations is larger than in the L relations

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Scientific conclusions

• We find no significant relationship between the outer slope of the RCs and optical/NIR photometric parameters.

• On the other hand, rotational widths are strongly correlated with photometric parameters.

• Those correlations show that: – more massive galaxies are brighter and redder--no surprises– TF scatter is greater at bluer wavelengths (at least for SDSS

bands) – All other things being equal, TFR should be a better distance

indicator in redder bands – in contradiction with the results of Pizagno et al. 2006

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Future work

• Publish the RC data set to the VO• Refine the analysis presented here, applying

corrections to the photometric quantities (e.g., extinction)

• Obtain average RCs in SB intervals at different ’s using 2MASS and SDSS data

• Present these fantastic results at the AAS meeting in Seattle using the NVO’s $500 check

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Conclusions: what we learned from the NVO SS

We learned and demonstrated how to:• make VOTables, MySQL databases, and

web interface to access our data set• cross-match our RC database with 3

large datasets• Use the power of the VO to obtain

science results… at light speed!!!