Towards an HI census of the Local Universe: further adventures in NIBLES Tana Joseph

Overview  What is NIBLES?  The HI data  The optical data Some curious results Some curious results Re-analysis of the photometry Re-analysis of the photometry  Implications

What is NIBLES?  NIBLES: Nançay Interstellar Baryonic Legacy Extragalactic Survey  Quantify HI content of galaxies in the Local Universe  4000 SDSS galaxies with 900< cz < km/s (Local Universe) 900< cz < km/s (Local Universe) -10 m > M z > -24 m -10 m > M z > -24 m All morphological types All morphological types

The HI data  Preliminary HI data for 600 galaxies  Compared to NHICAT data (Wong et al., 2006) Velocities agree well with NHICAT data Velocities agree well with NHICAT data  HI data reliable

Some curious results  Preliminary results: very high mass to light ratios

What could the problem be?  Are these data points real? No other systems found with such high M HI /L (Warren et al., 2006, van Zee, 2001) No other systems found with such high M HI /L (Warren et al., 2006, van Zee, 2001) Highest: M HI /L B = 22 M  /L  Highest: M HI /L B = 22 M  /L   Since HI data ok, photometry probably at fault Incorrect magnitudes due to circular aperture? Incorrect magnitudes due to circular aperture? But Strauss et al., 2002 find no problems for highly inclined systems But Strauss et al., 2002 find no problems for highly inclined systems

What could the problem be?  Optical “confusion” sources? E.g. SDSS and SDSS (M B =-13 m,M HI /L B = 367 M  /L  ) E.g. SDSS and SDSS (M B =-13 m,M HI /L B = 367 M  /L  ) are part of NGC0493 (M B =-20 m,M HI /L B = 0.5 M  /L  ) Not enough to account for all high M HI /L values Not enough to account for all high M HI /L values

Re-analysis of the photometric data  Individual photometry performed on a subsample of 403 galaxies out of 1385 (g band) a subsample of 403 galaxies out of 1385 (g band) All galaxies in range -10 m > M z > -14 m (i band) All galaxies in range -10 m > M z > -14 m (i band) Using Source Extractor and JPK’s pipeline Using Source Extractor and JPK’s pipeline

 m SE - m SDSS vs. Petrosian radius The g band photometry  g band magnitude comparison

 m SE - m SDSS vs. Petrosian radius The I band photometry  i band magnitude comparison

Re-analysis of the photometric data  Galaxies with R P < 8’’ have underestimated magnitudes in both g and i bands  Excising sources with R P < 8” gives much better agreement between SDSS and SE data

Re-analysis of the photometric data  M HI /L g re-determined using SDSS magnitudes for R P > 8” and SE magnitudes for R P 8” and SE magnitudes for R P < 8”

Re-analysis of the photometric data  M HI /L i re-determined using SDSS magnitudes for R P > 8” and SE magnitudes for R P 8” and SE magnitudes for R P < 8”

Implications  No galaxies with M g > -13 m and M i > -12 m remain when using SE data for sources with R P -13 m and M i > -12 m remain when using SE data for sources with R P < 8” !  Implications for various studies using SDSS photometry: The Luminosity function of the Local Universe The Luminosity function of the Local Universe Galaxy formation and evolution theories and models Galaxy formation and evolution theories and models

Thank you