Timescale of Stellar Feedback-Driven Turbulence in the ISM: A Deep Dive into UGC 4305

Understanding the interplay of stellar feedback and turbulence in the interstellar medium (ISM) is essential to modeling the evolution of galaxies. To determine the timescales over which stellar feedback drives turbulence in the ISM, we performed a spatially resolved, multi-wavelength study of the nearby star-forming dwarf galaxy UGC 4305 (aka Holmberg II). As indicators of turbulence on local scales (400 pc), we utilized ionized gas velocity dispersion derived from IFU H$\alpha$ observations and atomic gas velocity dispersion and energy surface densities derived from HI synthesis observations with the Very Large Array. These indicators of turbulence were tested against star formation histories over the past 560 Myr derived from Color-Magnitude Diagrams (CMD) using Spearman's rank correlation coefficient. The strongest correlation identified at the 400 pc scale is between measures of HI turbulence and star formation 70-140 Myr ago. We repeated our analysis of UGC 4305's current turbulence and past star formation activity on multiple physical scales ($\sim$560, and 800 pc) to determine if there are indications of changes in the correlation timescale with changes to the physical scale. No notable correlations were found at larger physical scales emphasizing the importance of analyzing star formation driven turbulence as a local phenomenon.Comment: 17 pages, 9 figure, accepted to A

Case Reports1. A Late Presentation of Loeys-Dietz Syndrome: Beware of TGFβ Receptor Mutations in Benign Joint Hypermobility

Background: Thoracic aortic aneurysms (TAA) and dissections are not uncommon causes of sudden death in young adults. Loeys-Dietz syndrome (LDS) is a rare, recently described, autosomal dominant, connective tissue disease characterized by aggressive arterial aneurysms, resulting from mutations in the transforming growth factor beta (TGFβ) receptor genes TGFBR1 and TGFBR2. Mean age at death is 26.1 years, most often due to aortic dissection. We report an unusually late presentation of LDS, diagnosed following elective surgery in a female with a long history of joint hypermobility. Methods: A 51-year-old Caucasian lady complained of chest pain and headache following a dural leak from spinal anaesthesia for an elective ankle arthroscopy. CT scan and echocardiography demonstrated a dilated aortic root and significant aortic regurgitation. MRA demonstrated aortic tortuosity, an infrarenal aortic aneurysm and aneurysms in the left renal and right internal mammary arteries. She underwent aortic root repair and aortic valve replacement. She had a background of long-standing joint pains secondary to hypermobility, easy bruising, unusual fracture susceptibility and mild bronchiectasis. She had one healthy child age 32, after which she suffered a uterine prolapse. Examination revealed mild Marfanoid features. Uvula, skin and ophthalmological examination was normal. Results: Fibrillin-1 testing for Marfan syndrome (MFS) was negative. Detection of a c.1270G > C (p.Gly424Arg) TGFBR2 mutation confirmed the diagnosis of LDS. Losartan was started for vascular protection. Conclusions: LDS is a severe inherited vasculopathy that usually presents in childhood. It is characterized by aortic root dilatation and ascending aneurysms. There is a higher risk of aortic dissection compared with MFS. Clinical features overlap with MFS and Ehlers Danlos syndrome Type IV, but differentiating dysmorphogenic features include ocular hypertelorism, bifid uvula and cleft palate. Echocardiography and MRA or CT scanning from head to pelvis is recommended to establish the extent of vascular involvement. Management involves early surgical intervention, including early valve-sparing aortic root replacement, genetic counselling and close monitoring in pregnancy. Despite being caused by loss of function mutations in either TGFβ receptor, paradoxical activation of TGFβ signalling is seen, suggesting that TGFβ antagonism may confer disease modifying effects similar to those observed in MFS. TGFβ antagonism can be achieved with angiotensin antagonists, such as Losartan, which is able to delay aortic aneurysm development in preclinical models and in patients with MFS. Our case emphasizes the importance of timely recognition of vasculopathy syndromes in patients with hypermobility and the need for early surgical intervention. It also highlights their heterogeneity and the potential for late presentation. Disclosures: The authors have declared no conflicts of interes

Timescale of Stellar Feedback-driven Turbulence in the ISM: A Deep Dive into UGC 4305

Understanding the interplay of stellar feedback and turbulence in the interstellar medium (ISM) is essential to modeling the evolution of galaxies. To determine the timescales over which stellar feedback drives turbulence in the ISM, we performed a spatially resolved, multiwavelength study of the nearby star-forming dwarf galaxy UGC 4305. As indicators of turbulence on local scales (400 pc), we utilized ionized gas velocity dispersion derived from IFU H α observations and atomic gas velocity dispersion and energy surface densities derived from H i synthesis observations with the Very Large Array. These indicators of turbulence were tested against star formation histories over the past 560 Myr derived from color–magnitude diagrams using Spearman’s rank correlation coefficient. The strongest correlation identified at the 400 pc scale is between measures of H i turbulence and star formation 70–140 Myr ago. We repeated our analysis of UGC 4305's current turbulence and past star formation activity on multiple physical scales (∼560 and 800 pc) to determine whether there are indications of changes in the correlation timescale with changes to the physical scale. No notable correlations were found at larger physical scales, emphasizing the importance of analyzing star formation-driven turbulence as a local phenomenon