Authors: Sarah Parker, Alyssa Likeness Faculty Mentor: Adriana Durbala Abstract: We explore the properties of lenticular galaxies in different environments (isolated galaxies versus crowded environments, i.e., groups with 4-10 galaxy members). Using a Fortran code (BUDDA – Bulge Disk Decomposition Analysis), we model the photometric parameters that describe each lenticular galaxy in terms of size and light profile. We then compare the derived model-dependent measures between the two samples of galaxies to test if they are statistically different, which would hint at gravitational influences of the neighbors. This process would allow us to gain more insight into the formation and evolution of lenticular galaxies. Sample: N=12 CIG (isolated) & N=28 LGG (group) S0 galaxies available images in SDSS DR8 CIG – Catalog of Isolated Galaxies 1500 < V Recession < 5500 km/s inclination < 70 LGG – Lyon Group of Galaxies Hubble image; Drory & Fisher 2007 Hubble image; Drory & Fisher 2007 PSEUDO BULGE CLASSICAL BULGE Acknowledgements This research was made possible due to the support of the Wisconsin Space Grant Consortium. Funds were provided by the Undergraduate Research Award and the Undergraduate Spring Scholarship Award under NASA Training Grant #NNX15AJ12H. 1. It has been proposed that galaxies with bulge contribution L bulge /L total < 0.1 (10%) contain pseudobulges. None of our galaxies meet this criterion. 2. A less restrictive criterion contains the proposal that all bulges characterized by n bulge < 2.5 and L bulge /L total < 0.45 (45%) are pseudobulges; our CIG (isolated) galaxy sample then contains 42% and our LGG (group) sample 68% pseudobulges. For SOa/Sa/Sab galaxies the CIG (isolated) sample contains 48% and the LGG (group) sample 28% pseudobulges. An isolated sample of Sb/Sbc/Sc galaxies contains 94 % pseudobulges using criterion 2. For E galaxies, both the LGG (group) sample and CIG (isolated) sample contain 0% pseudobulges. R h / r o e I ) r ( I ] 1 n / 1 ) e r / r [( n b e 10 I ) r ( I BUDDA Fortran Code (BUlge/Disk Decomposition Analysis)- de Souza et al. 2004 Disk: (Exponential profile) Bulge and Bar: (Sérsic profile) Bulge/Disk /Bar Image Decomposition I o – central intensity h R – radial scalelength I e - effective intensity r e – effective radius n – Sérsic index 3 out of 12 (25%) of CIG galaxies have bars. 12 out of 28 (43%) of LGG galaxies have bars. • Left Histograms: The LGG (group) sample and CIG (isolated) sample have similar disk scalelengths overall. However, galaxies without bars have larger disk scalelengths than barred galaxies. • Right Histograms: The LGG (group) sample galaxies are similar to the CIG (isolated) sample overall. Additionally, the non-barred galaxies for each sample are larger than their barred counterparts. 0 2 4 6 8 10 12 14 16 0 4 8 12 16 Mean: 2.79 0.21 Median: 2.66 LGG bar Disk Radial Scalelength (kpc) 0 2 4 6 8 10 12 14 16 0 1 2 3 4 5 Mean: 5.38 1.31 Median: 3.32 LGG 0 2 4 6 8 10 12 14 16 0 1 2 3 4 5 Mean: 2.25 0.09 Median: 2.27 Number of Galaxies CIG bar Comparison of Disk Radial Scalelength for Barred and Non-Barred Galaxies 0 2 4 6 8 10 12 14 16 0 1 2 3 4 5 Mean: 4.71 1.15 Median: 4.26 CIG 0.1 0.2 0.3 0.4 0.5 0.6 0.7 1 2 3 4 5 6 LGG (group galaxies) CIG (isolated galaxies) Sersic Index of Bulge (n bulge ) Luminosity Ratio (L bulge /L Total ) Sersic Index vs Luminosity Ratio 5 10 15 20 25 30 35 40 45 50 -19 -20 -21 -22 -23 -24 LGG (group galaxies) CIG (isolated galaxies) Absolute Magnitude Diameter (kpc) Absolute Magnitude vs Diameter 0.1 0.2 0.3 0.4 0.5 0.6 0 2 4 6 8 Mean: 0.26 0.02 Median: 0.25 Luminosity Ratio L bulge /L Total LGG barred 0.1 0.2 0.3 0.4 0.5 0.6 0 2 4 6 8 Mean: 0.42 0.03 Median: 0.41 Number of Galaxies LGG 0.1 0.2 0.3 0.4 0.5 0.6 0 1 2 Mean: 0.39 0.12 Median: 0.39 CIG barred Comparison of Luminosity Ratio for Barred and Non-Barred Galaxies 0.1 0.2 0.3 0.4 0.5 0.6 0 1 2 3 4 Mean: 0.44 0.05 Median: 0.41 CIG 0 10 20 30 40 50 0 2 4 6 8 Mean: 17.34 1.87 Median: 15.40 Galaxy Diameter (kpc) LGG barred 0 10 20 30 40 50 0 1 2 3 4 5 Mean: 22.75 2.97 Median: 21.77 LGG Comparison of Galaxy Diameter for Barred and Non-Barred Galaxies 0 10 20 30 40 50 0 1 2 3 Mean: 11.01 3.90 Median: 7.96 Number of Galaxies CIG barred 0 10 20 30 40 50 0 2 4 6 Mean: 20.62 3.04 Median: 17.70 CIG 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 4 8 12 Mean: 0.54 0.05 Median: 0.52 Effective Radius of Bulge, r e (kpc) LGG barred Comparison of Effective Radius of Bulge for Barred and Non-Barred Galaxies 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 2 4 6 8 Mean: 1.17 0.26 Median: 0.90 LGG 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 1 2 3 Mean: 0.87 0.12 Median: 0.80 Number of Galaxies CIG barred 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 2 4 6 8 Mean: 0.98 0.12 Median: 0.92 CIG Conclusions and Future Work • Lenticular galaxies in group (nurtured) environments tend to have smaller bulges and a higher percentage of pseudobulges than those in isolated environments. This difference is not noticeable for spiral morphological types. This might suggest that lenticular galaxies in group environments are more likely to form secularly than isolated galaxies. Typically, galaxies in group environments form by mergers and isolated form by secular evolution. This suggests that isolated lenticulars more likely have consumed all of their neighbors more recently. Another possibility is that pseudobulges could also be formed by mergers for lenticular morphological types. • Non-barred galaxies are larger and have more luminous bulges than barred galaxies, suggesting that bars take away material from the bulge during the galaxy’s formation. • The color of the galaxies correlates with the absolute magnitude. • In the future, we could perform bulge-disk-bar decomposition of each galaxy in the g-band, and compare the colors for the bulges. • Left Histograms: Compared to CIG (isolated) galaxies, the LGG (group) galaxy bulges tend to be smaller overall. Galaxies without bars have larger bulges than barred galaxies. This effect is more prominent in the LGG (group) sample. • Right Histograms: The luminosity ratio is smaller overall for LGG (group) galaxies compared to CIG (isolated) galaxies. Galaxies without bars have more luminous bulges compared to barred galaxies. In the CIG (isolated) sample it is unclear whether this is meaningful, due to poor statistics. • Top Right Graph: Larger galaxies tend to be more luminous, while smaller galaxies tend to be less luminous. • Middle Right Graph: More luminous galaxies are slightly bluer than less luminous galaxies. Isolated Galaxy (CIG) Galaxy in the Loose Group Sample (LGG) Residual Image Original Image - i band Total Model PGC 5766 Bulge Model No Bar Disk Model Bar Model Disk Model Bulge Model Residual Image Original Image - i band Total Model PGC 53201 Pseudobulges are shaped more like a disk, similar to a miniature spiral galaxy. Typically, galaxies with pseudobulges form through secular evolution. Classical bulges are more ellipsoidal in shape, similar to a miniature elliptical galaxy. Typically, galaxies with classical bulges are formed by mergers. -19 -20 -21 -22 -23 -24 0.0 0.5 1.0 1.5 Color vs. Absolute Magnitude LGG (group galaxies) CIG (isolated galaxies) Color (g-i) Absolute Magnitude