Strong Gravitational Lensing as a Probe of Cosmology and Galaxy Evolution at Sub-Galactic Scales

strong lensing;galaxy evolution;sub-galactic structure;Physics

Xu, BingxiaoNorman, Colin ;

Johns Hopkins University

关键词: strong lensing;    galaxy evolution;    sub-galactic structure;    Physics;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/60233/XU-DISSERTATION-2017.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

The main aim of my thesis work is to understand galaxy evolution at higher spatial resolution awarded by strong lensing. To achieve that, I have performed systematic studies focusing on three different aspects of the strongly lensed galaxies (giant arcs) in CLASH survey. In the first, I study the abundance of the strongly lensed galaxies in CLASH survey. I have devised an automated arcfinder to search giant arcs in CLASH images. After correcting the incompleteness and false positive rate, I find that at least for a sample of 20 clusters, the predicted arc abundance based on $Lambda$CDM is remarkably consistent with the observed abundance, which is $sim m 4 pm 1$. I also have performed extensive simulations to test the sensitivity of arc abundance to different physical parameters. I find that the arc abundance is more sensitive to the inner mass profile of galaxy clusters than the redshift distribution of background galaxies. The second part is to study the physical properties of thelensed galaxies including the stellar mass, star formation rate (SFR), specific star formation rate (sSFR), color, etc. The strong lensing generally selects galaxies that have lower mass than those from field survey. Majority of CLASH lensed galaxies have mild star formation rate with median value $sim m 4M_{odot}yr^{-1}$. I reconstruct the images of CLASH giant arcs in their source plane based on CLASH mass models and study the morphology of the galaxies in the source plane. Most of them lie in the irregular region in the Gini-M20 plane, which is consistent with that the low-mass galaxies at high-z typically have clumpy and irregular morphology. In the third study, I explore the sub-galactic structures (clumps) identified in the source plane reconstructed images. I study various physical properties of the sub-galactic structures (clumps) such as stellar mass, SFR, sSFR, color, size and compactness. I also have quantified therest-frame UV luminosity function (LF) and stellar mass function (SMF) of clumps at different redshifts. The main results are: the clumps at high-z are typically more massive and compact; the high-z clumps have very similar structural properties to the dwarf spheroidals at low-z, which implies possible evolutionary link between two species; the faint end and low mass end slopes of rest-frame UV LF and SMF are flatter than those of galaxy at similar redshifts; the high mass end of clumps SMF at high-z is very well consistent with the SMF of bulge in late-type disk galaxies with similar abundance, which suggests the massive clumps at high-z are likely progenitors of today;;s bulge; intriguingly, the most massive clumps at high-z are also rest-frame UV brightest, which implies that the mass assembly of bulges proceeds mainly via some dissipative process rather than the ``dry;; growth which is predicted by the some theoretical models; the spatial distribution of clumps and its evolution are consistent with that the clumps do not migrate towards the galactocenter or migrate very slowly in low-mass galaxies. Combining the above evidence, I propose a brand new picture of galaxy evolution to simultaneously explain the formation of the today;;s Hubble sequence, formation of the galactic bulges and origin of the dwarf spheroids in dense environments.