|   | 
				
					
	
		  | 
	 
	
		| Paper: | 
		New Constraints on Dark Matter Substructure from Weak Gravitational Flexion | 
	 
	
		| Volume: | 
		379, Cosmic Frontiers | 
	 
	
		| Page: | 
		338 | 
	 
	
		| Authors: | 
		Rowe, B.; Bacon, D.; Heymans, C.; Taylor, A.; Massey, R.; Barden, M.; Caldwell, J.A.R. | 
	 
	
	
		| Abstract: | 
		We place a first weak lensing constraint on the degree of substructure present in the Universe using a determination of the width of the measured flexion distribution for galaxies in the HST-GEMS survey. This then places a robust upper limit on the gravitational flexion variance at the angular scales of the GEMS galaxy images themselves. The sensitivity of flexion to small-scale power allows this measurement to restrict the substructure mass fraction in this field to a value fm < 0.4, for a mass variance σ8 = 0.9. We briefly discuss the potential for this method to further improve upon this constraint. | 
	 
	
		| 
			
			
		 | 
	 
	
		  | 
	 
 
					 
				 | 
				  |