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Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Thijs van der Hulst
Kapteyn Astronomical InstituteUniversity of Groningen
Galaxies in Voids:special or not?
and the Void Gang:
Kathryn Kreckel (Heidelberg), Burcu Beygu (Groningen), Rien van de Weygaert (Groningen), Jacqueline van Gorkom (New York), Miguel Aragon Calvo (Baltimore), Tom Jarrett (Cape Town), Reynier Peletier (Groningen), ...
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Thijs van der Hulst
Kapteyn Astronomical InstituteUniversity of Groningen
Galaxies in Voids:special of not?
and the Void Gang:
Kathryn Kreckel (Heidelberg), Burcu Beygu (Groningen), Rien van de Weygaert (Groningen), Jacqueline van Gorkom (New York), Miguel Aragon Calvo (Baltimore), Tom Jarrett (Cape Town), Reynier Peletier (Groningen), ...
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Why Voids?
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
- Voids are the most empty regions in the universe
- Voids do still have fine structure: filaments, walls
- Voids evolve and merge
- Substructure in voids expected to form galaxies
- Expect galaxies to evolve ‘quietly’, no harrasment
distribution of local galaxies from SDSS
but: finding voids is not trivial !
Sunday, October 6, 2013
Different void finders give different results:
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Geometric void selectionDTFE (Schaap & van de Weygaert 2000) plus Watershed Void Finder (Platen et al. 2007)
Sunday, October 6, 2013
• red gals., g-r > 0.6 • blue gals., g-r < 0.6
the galaxy environment of VGS_58, selected from SDSS
An example: VGS_58
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
- multiwavelength survey of 60 void galaxies SDSS u, g, r, i, z; deep B imaging, Halpha imaging GALEX NUV, Spitzer 3.6 and 4.5 micron, WSRT HI
- probe morphology, gas content, star formation properties, stellar masses, colours, etc.
- voids selected using pure geometrical methods- galaxies and voids selected from SDSS DR7- no a priori assumption about the shape of the voids- no a priori assumption about the scale of the voids- galaxy selection independent of their properties
The Void Galaxy Survey (Kreckel et al. AJ 144, 16, 2012)
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
● Void galaxies are blue (Grogin & Geller 1999, Rojas et al. 2004, Croton et al. 2005).
● They have high SFR (Grogin & Geller 1999, Rojas et al. 2004, Gonzales & Padilla 2009).
● They have mostly late – type morphologies (Dressler 1980, Postman& Geller 1984, Croton et al. 2005, Hoyle et al. 2005).
● Their stellar population is young (Grogin & Geller 2000, Kauffmann et al. 2004, Rojas et al. 2005).
● They have low stellar mass (Croton et al. 2005, Goldberg et al. 2005).
Previous results on Void galaxies
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
HI results
- 41 detections and 14 non-detections - HI mass range 2 x 107 to 6 x 109 Msun
- mostly small disk galaxies, three early type galaxies- many have signs of interactions, asymmetries- HI contents are normal- stellar masses all less than 3 x 1010 Msun
Kreckel et al. AJ 144, 16, 2012
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
ALFALFA galaxies at δ + 1 < 1Void galaxies
HI contentcomparison with control sample from ALFALFA
selected to be at densities δ + 1 < 10
Kreckel et al. AJ 144, 16, 2012
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
ALFALFA galaxies at δ + 1 < 1Void galaxies
HI contentcomparison with control sample from ALFALFA
selected to be at densities δ + 1 < 10
Kreckel et al. AJ 144, 16, 2012
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Remarkable galaxiesVGS _ 12
Huge polar disk in thin wall: accretion in action from the neighbouring voids?
Interacting group inside a void, aligned along LSS filament?
Galaxies not very different from galaxies elsewhere: but have systematically small stellar mass
VGS_31(Stanonik et al. 2009)
(Beygu et al. 2013)
(Kreckel et al. 2012)
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
- MDM Halpha imaging, GALEX NUV, Spitzer 3.6 and 4.5 micron- stellar masses from MPA-JHU catalog based on SDSS- HI masses from WSRT 21cm imaging
Examine: Star Formation Rate Specific Star Formation Rate Star Formation efficiency
- comparison samples: Halpha survey of galaxies from ALFALFA (Gavazzi et al 2013) Local Volume galaxies (Karachentsev et al. 2013) JCMT field galaxies (Sanchez - Gallego et al. 2012)
Star Formation properties (Beygu et al. in preparation)
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Star Formation Efficiency and Specific SFR
Sunday, October 6, 2013
Galaxy Evolution Over Five Decades, Cambridge 3 - 6 September 2013
Conclusions
- void galaxies very similar to galaxies in other, moderate density environments
- local environment more important than global environment?
- void galaxies are in general small disks
- SF properties normal, except for a few high HI mass systems
work in progress: stay tuned
Sunday, October 6, 2013