This project is conducted in Fall 2014.
I use GALFIT to model the galaxies to better detect the faint objects around them (especially GCs). Normally I use sérsic model or double sérsic model for inner part and outer part.
First I select the galaxies that I am interested
NGC4531, IC3540, IC3586, M89
Then I use models to fit them with some varying parameters (elongation, position angle, etc. ) , here's an example.
Left: IC3586 in g band. Right: Residue image
This project is ongoing, for more, see the preprint paper (still working on it, or the Google Drive file)
Globular culsters (GC) are the tracers of galaxy evolution, richness and other properties of GC
systems can help make clear formation history and constrain models.
Thanks to the deep image from Next Generation Virgo Cluster Survey (NGVS), we have calculated specific frequency (SN, scale of richness normalized to luminosity) for 20 nucleated dwarf ellipticals (dE,Ns) in Virgo cluster, all of which are fainter than MV = -16.5, and found that their SN is significantly larger and scattered than massive galaxies and the trend shows SN increases monotonically with MV at MV > -16.5 (see fig.1). We also studied GC color distribution and the influence of environment on GC richness of galaxies.
We confirmed the U-shape in SN MV relationship at low luminosity end. Our result favors the stripping model (or intrinsically quenching model?).
for more, see the undergoing paper
This project is conducted in Spring 2015
Using python package aplpy, I combine the u,g,z band image from NGVS to create a colored image, the examples are following:
This project is conducted in Fall 2014
It is important to investigate the high-redshift galaxies through spectroscopy or photometry because they trace the early universe. I utilized the Lyman break to obtain the redshift value. It can roughly estimate the photometric redshift through color-color diagrams and we successfully selected redshift around 3,4 and 5.
Instead of looking for featured spectral lines, we look for the dropout of flux in some of the bands that we call Lyman Break@912Å, which is caused by the absorption of gas.
At z=3, Lyman Break is at about 4000Å, so the dropout should be in U band (center wavelength=3660 Å). So magnitude in B band and U band should be large compared to the difference in B band and bands with larger center wavelength.