HI studies of Low Surface Brightness Galaxies with the Nancay Radio Telescope

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1 HI studies of Low Surface Brightness Galaxies with the Nancay Radio Telescope Honey M Indian Institute of Astrophysics, Bangalore Collaborators Dr. Jean-Michel Martin Observatoire Paris-Site de Meudon, GEPI, France Dr. Mamta Pandey-Pommier CRAL, Observatoire de Lyon, France. Dr. Mousumi Das Indian Institute of Astrophysics, Bangalore

2 Low Surface Brightness Galaxies (LSBGs) They are optically dim, disk dominated systems. They usually have central disk brightness greater than 22 magnitude /arcsec2 in B- band (Sprayberry et al.1995) They are rich in HI, but have low star formation rates ( Impey and Bothun. 1994). Have large HI disks that extends far beyond the stellar disks. They are Dark matter dominated systems ( de Blok et al. 2002). Metal poor & have low dust content Image courtesy: SDSS DR12 Sprayberry et al,1995aj,109

3 They are extreme late type galaxies. They can be broadly divided into two groups (i)low surface brightness dwarfs and irregulars (ii) large spiral galaxies (Gaint LSB galaxies). The Giant LSB galaxies are rarer and usually seen in isolated environments. They are often found close to the edges of voids. Low Surface Brightness galaxies and the large scale structure of local universe. Green points mark Bright galaxies and black points represent GLSB galaxies Rosenbaum et al.2009, A&A 504

4 Giant Low Surface Brightness(GLSB) Galaxies A good fraction of GLSB galaxies have prominent bulges and some of them even show nuclear activity ( Sprayberry et al. 1995;Galaz et al. 2011, Ramya et al. 2011). They have low density stellar disks. They have weak spiral arms and bars are not common. They have massive HI disks that extend well beyond the stellar disks. Molecular hydrogen is rarely found UGC 6614 UM 163

5 Aim To check the HI profile of LSB galaxies Whether the HI mass is correlated with the Stellar mass & color of the galaxy Sample Used three LSB catalogs (Impey et al & Schombert et al. 1988, Schombert et al ) Visually examined HIPASS spectra of 842 LSB galaxies, and 100 of them found to have good HI emission line. 20 of them are not have earlier HI studies

6 Observations with Nancay Radio Telescope Location- Nançay, France Declination limit 39 Operating frequencies-1400 MHz(21 cm), 1660 MHz(18 cm), 3330 MHz(9 cm). Bandwidth MHz. Frequency resolution- 6.1 Khz Data Analysis Used CLASS (Continuum and Spectral-Line Analysis Software, from IRAM/Grenoble) Nançay radio telescope

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8 Calculation of HI mass from HI flux The HI fluxes were measured from their line spectra LSBC F Image courtesy : SDSS DR12

9 Calculation of Stellar mass We have used the SDSS DR12 archival data The I-band flux is used to determine the stellar luminosity The color (g-r) is converted to (B-V) using transformation equations( Jester et al.2005) (B-V)= 0.98 x (g-r) (B-V) is used to determine the (M/L) ( Bell & de Jong. 2001) Stellar mass is calculated using

10 Whether the HI mass & Stellar mass are correlated in LSBs?

11 Color of LSBs how related to M H /M stellar?

12 Magnitude Vs M H /M stellar

13 Results We have single dish HI observations of 15 LSB galaxies. Observations are still ongoing for the rest of the sample. Faint trend of increasing HI mass with stellar mass, we will compare this with normal galaxies and LSB dwarfs. Faint trend of increasing HI mass with (g-r) color, however these results are only tentative. There is no trend of R magnitude with M HI / M stellar In general, from the slopes of the curves it appears that these galaxies are evolving very slowly. Future work To look for the mass of dark matter content using the dynamical mass, M HI & M stellar and examine how the M HI is correlated with it.

14 References Impey, & Bothun, G. 1997, ARA&A, 35, 267 Pickering, T. E.; Impey, C. D.; van Gorkom, J. H.; Bothun, G. D. 1997, AJ, 114, 1858 de Blok, W. J. G.; Bosma, A.2002, A&A, 385, 816 McGaugh, Stacy S. 1994, ApJ, 426, 135 Rosenbaum et al.2009, A&A, 504 Impey, C. D.; Sprayberry, D.; Irwin, M. J.; Bothun, G. D. 1996, ApJS, 105, 209 Impey, C. D.; Sprayberry, D.; Irwin, M. J.; Bothun, G. D. 1996, ApJS, 105, 209 Schombert, James M.; Bothun, Gregory D.; Schneider, Stephen E.; McGaugh, Stacy S. 1992,AJ, 103, 1107 Jester et al. 2005, AJ, 130, 873 Bell, Eric F.; de Jong, Roelof S. 2001, ApJ, 550, 212

15 Thank you