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Dr Sarah Ragan
Cyfarwyddwr Astudiaethau Israddedig
- RaganSE@caerdydd.ac.uk
- +44 29208 74289
- Adeiladau'r Frenhines - Adeilad y Gogledd, Ystafell N/1.24, 5 The Parade, Heol Casnewydd, Caerdydd, CF24 3AA
- Ar gael fel goruchwyliwr ôl-raddedig
Trosolwyg
Rwyf wedi bod yn aelod o staff yr Ysgol Ffiseg a Seryddiaeth ers 2016, ac ar hyn o bryd rwy'n Uwch-ddarlithydd ac yn Gyfarwyddwr Astudiaethau Israddedig. Ers ennill fy PhD yn 2009 ym Mhrifysgol Michigan, Ann Arbor, rwyf wedi dal swyddi ymchwil yn Sefydliad Max Planck ar gyfer Seryddiaeth yn Heidelberg, Prifysgol Leeds a Phrifysgol Caerdydd. Dechreuais ar swydd academaidd yn 2018.
Mae fy ymchwil ar gamau cynnar ffurfio sêr, ac rwy'n defnyddio cyfuniad o dechnegau arsylwi a modelu i ddeall pa amodau mewn cymylau moleciwlaidd sy'n angenrheidiol ar gyfer ffurfio sêr, sydd o'r amodau hynny'n hyrwyddo ffurfio sêr màs uchel yn benodol, a beth sy'n achosi ffurfio'r cymylau moleciwlaidd yn y lle cyntaf. Mae ein hymchwil wedi dangos bod y pynciau hyn i gyd yn gysylltiedig, ac yn gysylltiedig â'r amgylchedd ehangach yn y Galaxy hefyd!
Cyhoeddiad
2024
- Fehér, O., Ragan, S. E., Priestley, F. D., Clark, P. C. and Moore, T. J. T. 2024. N2H+(1–0) as a tracer of dense gas in and between spiral arms. Monthly Notices of the Royal Astronomical Society 530(2), pp. 1311–1327. (10.1093/mnras/stae918)
- Rigby, A. J. et al. 2024. The dynamic centres of infrared-dark clouds and the formation of cores. Monthly Notices of the Royal Astronomical Society 528(2), pp. 1172–1197. (10.1093/mnras/stae030)
2023
- Priestley, F. D., Clark, P. C., Glover, S. C. O., Ragan, S. E., Feher, O., Prole, L. R. and Klessen, R. S. 2023. NEATH – II. N2H+ as a tracer of imminent star formation in quiescent high-density gas. Monthly Notices of the Royal Astronomical Society 526(4), pp. 4952–4960. (10.1093/mnras/stad3089)
- Priestley, F. D., Clark, P. C., Glover, S. C. O., Ragan, S. E., Feher, O., Prole, L. R. and Klessen, R. S. 2023. Non-equilibrium abundances treated holistically (NEATH): the molecular composition of star-forming clouds. Monthly Notices of the Royal Astronomical Society 524(4), pp. 5971–5983. (10.1093/mnras/stad2278)
- Ahmadi, A. et al. 2023. Kinematics and stability of high-mass protostellar disk candidates at sub-arcsecond resolution. Astronomy & Astrophysics 677, article number: A171. (10.1051/0004-6361/202245580)
2022
- Wells, M. R. A. et al. 2022. ATLASGAL - star forming efficiencies and the Galactic star formation rate. Monthly Notices of the Royal Astronomical Society 516(3), pp. 4245–4255. (10.1093/mnras/stac2420)
- Neralwar, K. R. et al. 2022. The SEDIGISM survey: Molecular cloud morphology II. Integrated source properties. Astronomy & Astrophysics 664(2022), article number: A84. (10.1051/0004-6361/202142513)
- Neralwar, K. R. et al. 2022. The SEDIGISM survey: Molecular cloud morphology. Astronomy & Astrophysics 663, article number: A56. (10.1051/0004-6361/202142428)
- Urquhart, J. S. et al. 2022. ATLASGAL - evolutionary trends in high-mass star formation. Monthly Notices of the Royal Astronomical Society 510(3), pp. 3389–3407. (10.1093/mnras/stab3511)
- Colombo, D. et al. 2022. The SEDIGISM survey: the influence of spiral arms on the molecular gas distribution of the inner Milky Way. Astronomy & Astrophysics 658, pp. 1-38., article number: A54. (10.1051/0004-6361/202141287)
2021
- Anderson, M. et al. 2021. An ALMA study of hub-filament systems - I. On the clump mass concentration within the most massive cores. Monthly Notices of the Royal Astronomical Society 508(2), pp. 2964–2978. (10.1093/mnras/stab2674)
- Smith, M. W. L. et al. 2021. The HASHTAG project: The first submillimeter images of the Andromeda Galaxy from the ground.. Astrophysical Journal Supplement Series 257, article number: 52. (10.3847/1538-4365/ac23d0)
- Elia, D. et al. 2021. The Hi-GAL compact source catalogue - II. The 360° catalogue of clump physical properties. Monthly Notices of the Royal Astronomical Society 504(2), pp. 2742–2766. (10.1093/mnras/stab1038)
- Duarte Cabral, A. et al. 2021. The SEDIGISM survey: molecular clouds in the inner galaxy. Monthly Notices of the Royal Astronomical Society 500(3), pp. 3027-3049. (10.1093/mnras/staa2480)
- Urquhart, J. S. et al. 2021. SEDIGISM-ATLASGAL: dense gas fraction and star formation efficiency across the galactic disk. Monthly Notices of the Royal Astronomical Society 500(3), article number: staa2512. (10.1093/mnras/staa2512)
- Eden, D. J. et al. 2021. Characteristic scale of star formation. I. Clump formation efficiency on local scales. Monthly Notices of the Royal Astronomical Society 500(1), pp. 191-210. (10.1093/mnras/staa3188)
- Schuller, F. et al. 2021. The SEDIGISM survey: first data release and overview of the Galactic structure*. Monthly Notices of the Royal Astronomical Society 500(3), article number: staa2369. (10.1093/mnras/staa2369)
2020
- Henshaw, J. D. et al. 2020. Ubiquitous velocity fluctuations throughout the molecular interstellar medium. Nature Astronomy 4, pp. 1064-1071. (10.1038/s41550-020-1126-z)
- Eden, D. J. et al. 2020. CHIMPS2: survey description and 12CO emission in the Galactic centre. Monthly Notices of the Royal Astronomical Society 498(4), pp. 5936-5951. (10.1093/mnras/staa2734)
- Syed, J. et al. 2020. Atomic and molecular gas properties during cloud formation. Astronomy and Astrophysics 642, article number: A68. (10.1051/0004-6361/202038449)
- Wang, Y. et al. 2020. Dense gas in a giant molecular filament. Astronomy and Astrophysics 641, article number: A53. (10.1051/0004-6361/202037928)
- Beuther, H. et al. 2020. Dynamical cloud formation traced by atomic and molecular gas. Astronomy and Astrophysics 638, article number: A44. (10.1051/0004-6361/202037950)
- Mottram, J. C. et al. 2020. From clump to disc scales in W3 IRS4. Astronomy and Astrophysics 636, article number: A118. (10.1051/0004-6361/201834152)
- Li, Z. et al. 2020. The HASHTAG project I. A survey of CO(3–2) emission from the star forming disc of M31. Monthly Notices of the Royal Astronomical Society 492(1), pp. 195-290. (10.1093/mnras/stz3409)
- Wang, Y. et al. 2020. Cloud formation in the atomic and molecular phase: HI self absorption (HISA) towards a giant molecular filament. Astronomy and Astrophysics 634, article number: A139. (10.1051/0004-6361/201935866)
- Pettitt, A. R., Ragan, S. E. and Smith, M. C. 2020. Young stars as tracers of a barred-spiral Milky Way. Monthly Notices of the Royal Astronomical Society 4914(2), pp. 2162-2179. (10.1093/mnras/stz3155)
2019
- Rigby, A. J. et al. 2019. CHIMPS: physical properties of molecular clumps across the inner Galaxy. Astronomy and Astrophysics 632, article number: A58. (10.1051/0004-6361/201935236)
- Clark, P. C., Glover, S. C. O., Ragan, S. E. and Cabral, A. 2019. Tracing the formation of molecular clouds via [CII], [CI] and CO emission. Monthly Notices of the Royal Astronomical Society 486(4), pp. 4622-4637. (10.1093/mnras/stz1119)
- Henshaw, J. D. et al. 2019. ‘The Brick’ is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016. Monthly Notices of the Royal Astronomical Society 485(2), pp. 2457-2485. (10.1093/mnras/stz471)
- Rugel, M. R. et al. 2019. Feedback in W49A diagnosed with radio recombination lines and models. Astronomy and Astrophysics 622, article number: A48. (10.1051/0004-6361/201834068)
- Soler, J. D. et al. 2019. Histogram of oriented gradients: a technique for the study of molecular cloud formation. Astronomy and Astrophysics 622, article number: A166. (10.1051/0004-6361/201834300)
2018
- Rugel, M. et al. 2018. OH absorption in the first quadrant of the Milky Way as seen by THOR. Astronomy and Astrophysics 618, article number: A159. (10.1051/0004-6361/201731872)
- Ahmadi, A. et al. 2018. Core fragmentation and Toomre stability analysis of W3(H20): A case study of the IRAM NOEMA large program CORE. Astronomy and Astrophysics 618(46), article number: A46. (10.1051/0004-6361/201732548)
- Beuther, H. et al. 2018. Fragmentation and disk formation during high-mass star formation: the IRAM NOEMA (Northern Extended Millimeter Array) large program CORE. Astronomy and Astrophysics 617, article number: A100. (10.1051/0004-6361/201833021)
- Ragan, S. E., Moore, T. J. T., Eden, D. J., Hoare, M. G., Urquhart, J. S., Elia, D. and Molinari, S. 2018. The role of spiral arms in Milky Way star formation. Monthly Notices of the Royal Astronomical Society 479(2), pp. 2361-2373. (10.1093/mnras/sty1672)
- Barnes, A. T. et al. 2018. Similar complex kinematics within two massive, filamentary infrared dark clouds?. Monthly Notices of the Royal Astronomical Society 475(4), pp. 5268-5289. (10.1093/mnras/sty173)
2017
- Marsh, K. et al. 2017. Multi-temperature mapping of dust structures throughout the Galactic Plane using the PPMAP tool with Herschel Hi-GAL data. Monthly Notices of the Royal Astronomical Society 471(3), pp. 2730-2742. (10.1093/mnras/stx1723)
- Elia, D. et al. 2017. The Hi-GAL compact source catalogue. I. The physical properties of the clumps in the inner Galaxy (−71.0 ◦ < ` < 67.0◦). Monthly Notices of the Royal Astronomical Society 471(1), pp. 100-143. (10.1093/mnras/stx1357)
2016
- Ragan, S. E., Moore, T. J. T., Eden, D. J., Hoare, M. G., Elia, D. and Molinari, S. 2016. The prevalence of star formation as a function of Galactocentric radius. Monthly Notices of the Royal Astronomical Society 462(3), pp. 3123-3129. (10.1093/mnras/stw1870)
- Beuther, H. et al. 2016. The HI/OH/Recombination line survey of the inner Milky Way (THOR). Survey overview and data release 1. Astronomy and Astrophysics -Berlin then Les Ulis- 595, article number: A32. (10.1051/0004-6361/201629143)
- Marsh, K., Ragan, S., Whitworth, A. P. and Clark, P. 2016. Evidence that widespread star formation may be underway in G0.253+016, 'The Brick'. Monthly Notices of the Royal Astronomical Society 461(1), pp. L16-L20. (10.1093/mnrasl/slw080)
- Lippok, N. et al. 2016. Earliest phases of star formation (EPoS). Dust temperature distributions in isolated starless cores. Astronomy and Astrophysics -Berlin then Les Ulis- 592, article number: A61. (10.1051/0004-6361/201525792)
- Feng, S., Beuther, H., Zhang, Q., Henning, T., Linz, H., Ragan, S. and Smith, R. 2016. Are infrared dark clouds really quiescent?. Astronomy and Astrophysics -Berlin then Les Ulis- 592, article number: A21. (10.1051/0004-6361/201526864)
- Abreu-Vicente, J., Ragan, S., Kainulainen, J., Henning, T., Beuther, H. and Johnston, K. 2016. Giant molecular filaments in the Milky Way II. the fourth Galactic quadrant. Astronomy and Astrophysics 590, article number: A131. (10.1051/0004-6361/201527674)
- Bertram, E., Glover, S., Clark, P., Ragan, S. and Klessen, R. 2016. Synthetic observations of molecular clouds in a galactic centre environment - I. Studying maps of column density and integrated intensity. Monthly Notices of the Royal Astronomical Society 455(4), pp. 3763-3778. (10.1093/mnras/stv2619)
2015
- Beuther, H., Ragan, S. E., Johnston, K., Henning, T., Hacar, A. and Kainulainen, J. T. 2015. Filament fragmentation in high-mass star formation. Astronomy and Astrophysics 584, article number: A67. (10.1051/0004-6361/201527108)
- Walsh, A. et al. 2015. A survey for hydroxyl in the THOR pilot region around W43. Monthly Notices of the Royal Astronomical Society 455(4), pp. 3494-3510. (10.1093/mnras/stv2446)
- Beuther, H. et al. 2015. Hierarchical fragmentation and collapse signatures in a high-mass starless region. Astronomy and Astrophysics 581, article number: A119. (10.1051/0004-6361/201526759)
- Bihr, S. et al. 2015. THOR: The H i, OH, Recombination line survey of the Milky Way. The pilot study: H i observations of the giant molecular cloud W43. Astronomy and Astrophysics 580, article number: A112. (10.1051/0004-6361/201425370)
- Bihr, S. et al. 2015. Kinematic and thermal structure at the onset of high-mass star formation. Astronomy and Astrophysics 579, article number: A51. (10.1051/0004-6361/201321269)
- Ragan, S. E., Henning, T., Beuther, H., Linz, H. and Zahorecz, S. 2015. Fragmentation and kinematics of dense molecular cores in the filamentary infrared-dark cloud G011.11–0.12. Astronomy and Astrophysics 573, article number: A119. (10.1051/0004-6361/201424948)
- Tobin, J. et al. 2015. Characterizing the youngest Herschel-detected protostars. I. envelope structure revealed by CARMA dust continuum observations. Astrophysical Journal 798(2), article number: 128. (10.1088/0004-637X/798/2/128)
2014
- Beuther, H. et al. 2014. Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: cloud formation signatures and carbon gas fractions. Astronomy and Astrophysics 571, article number: A53. (10.1051/0004-6361/201424757)
- Ragan, S. E., Henning, T., Tackenberg, J., Beuther, H., Johnston, K. G., Kainulainen, J. and Linz, H. 2014. Giant molecular filaments in the Milky Way. Astronomy and Astrophysics 568, article number: A73. (10.1051/0004-6361/201423401)
- Johnston, K., Beuther, H., Linz, H., Schmiedeke, A., Ragan, S. and Henning, T. 2014. The dynamics and star-forming potential of the massive Galactic centre cloud G0.253+0.016. Astronomy and Astrophysics 568, article number: A56. (10.1051/0004-6361/201423943)
- Tackenberg, J. et al. 2014. Kinematic structure of massive star-forming regions. I. accretion along filaments. Astronomy and Astrophysics 565, article number: A101. (10.1051/0004-6361/201321555)
- Wang, K. et al. 2014. Hierarchical fragmentation and differential star formation in the Galactic `Snake': infrared dark cloud G11.11-0.12. Monthly Notices of the Royal Astronomical Society 439(4), pp. 3275-3293. (10.1093/mnras/stu127)
2013
- Ragan, S., Henning, T. and Beuther, H. 2013. APEX/SABOCA observations of small-scale structure of infrared-dark clouds I. early evolutionary stages of star-forming cores. Astronomy and Astrophysics 559(Novemb), article number: A79. (10.1051/0004-6361/201321869)
- Kainulainen, J., Ragan, S., Henning, T. and Stutz, A. 2013. High-fidelity view of the structure and fragmentation of the high-mass, filamentary IRDC G11.11-0.12. Astronomy and Astrophysics 557(Septem), article number: A120. (10.1051/0004-6361/201321760)
- Beuther, H. et al. 2013. Fragmentation and dynamical collapse of the starless high-mass star-forming region IRDC 18310-4. Astronomy and Astrophysics 553(May), pp. 115., article number: A115. (10.1051/0004-6361/201220475)
- Clark, P., Glover, S. C. O., Ragan, S., Shetty, R. and Klessen, R. S. 2013. On the temperature structure of the galactic center cloud G0.253+0.016. Astrophysical Journal Letters 768(2), article number: L34. (10.1088/2041-8205/768/2/L34)
- Pitann, J. et al. 2013. G048.66-0.29: physical state of an isolated site of massive star formation. Astrophysical Journal 766(2), article number: 68. (10.1088/0004-637X/766/2/68)
- Launhardt, R. et al. 2013. The Earliest Phases of Star Formation (EPoS): a Herschel key project: the thermal structure of low-mass molecular cloud cores. Astronomy and Astrophysics 551(March), article number: A98. (10.1051/0004-6361/201220477)
2012
- Nielbock, M. et al. 2012. The Earliest Phases of Star formation (EPoS) observed with Herschel: the dust temperature and density distributions of B68. Astronomy and Astrophysics 547(Novemb), article number: A11. (10.1051/0004-6361/201219139)
- Ragan, S. et al. 2012. The Earliest Phases of Star Formation (EPoS): a Herschel key program: the precursors to high-mass stars and clusters. Astronomy and Astrophysics 547(Novemb), article number: A49. (10.1051/0004-6361/201219232)
- Ragan, S., Heitsch, F., Bergin, E. and Wilner, D. 2012. Very large array observations of ammonia in infrared-dark clouds. II. internal kinematics. Astrophysical Journal 746(2), article number: 174. (10.1088/0004-637X/746/2/174)
- Beuther, H. et al. 2012. The onset of high-mass star formation in the direct vicinity of the Galactic mini-starburst W43. Astronomy and Astrophysics 538(Februa), article number: A11. (10.1051/0004-6361/201117850)
2011
- Ragan, S., Bergin, E. and Wilner, D. 2011. Very large array observations of ammonia in infrared-dark clouds. I. column density and temperature structure. Astrophysical Journal 736(2), article number: 163. (10.1088/0004-637X/736/2/163)
2010
- Henning, T. et al. 2010. The seeds of star formation in the filamentary infrared-dark cloud G011.11-0.12. Astronomy and Astrophysics 518, article number: A95. (10.1051/0004-6361/201014635)
2009
- Gibson, D., Plume, R., Bergin, E., Ragan, S. and Evans, N. 2009. Molecular line observations of infrared dark clouds. II. physical conditions. Astrophysical Journal 705(1), pp. 123-134. (10.1088/0004-637X/705/1/123)
- Ragan, S., Bergin, E. A. and Gutermuth, R. A. 2009. Detection of structure in infrared-dark clouds with Spitzer: characterizing star formation in the molecular ring. Astrophysical Journal 698(1), pp. 324-349. (10.1088/0004-637X/698/1/324)
2006
- Ragan, S., Bergin, E., Plume, R., Gibson, D., Wilner, D., O'Brien, S. and Hails, E. 2006. Molecular line observations of infrared dark clouds: seeking the precursors to intermediate and massive star formation. Astrophysical Journal Supplement 166(2), pp. 567-584. (10.1086/506594)
Erthyglau
- Fehér, O., Ragan, S. E., Priestley, F. D., Clark, P. C. and Moore, T. J. T. 2024. N2H+(1–0) as a tracer of dense gas in and between spiral arms. Monthly Notices of the Royal Astronomical Society 530(2), pp. 1311–1327. (10.1093/mnras/stae918)
- Rigby, A. J. et al. 2024. The dynamic centres of infrared-dark clouds and the formation of cores. Monthly Notices of the Royal Astronomical Society 528(2), pp. 1172–1197. (10.1093/mnras/stae030)
- Priestley, F. D., Clark, P. C., Glover, S. C. O., Ragan, S. E., Feher, O., Prole, L. R. and Klessen, R. S. 2023. NEATH – II. N2H+ as a tracer of imminent star formation in quiescent high-density gas. Monthly Notices of the Royal Astronomical Society 526(4), pp. 4952–4960. (10.1093/mnras/stad3089)
- Priestley, F. D., Clark, P. C., Glover, S. C. O., Ragan, S. E., Feher, O., Prole, L. R. and Klessen, R. S. 2023. Non-equilibrium abundances treated holistically (NEATH): the molecular composition of star-forming clouds. Monthly Notices of the Royal Astronomical Society 524(4), pp. 5971–5983. (10.1093/mnras/stad2278)
- Ahmadi, A. et al. 2023. Kinematics and stability of high-mass protostellar disk candidates at sub-arcsecond resolution. Astronomy & Astrophysics 677, article number: A171. (10.1051/0004-6361/202245580)
- Wells, M. R. A. et al. 2022. ATLASGAL - star forming efficiencies and the Galactic star formation rate. Monthly Notices of the Royal Astronomical Society 516(3), pp. 4245–4255. (10.1093/mnras/stac2420)
- Neralwar, K. R. et al. 2022. The SEDIGISM survey: Molecular cloud morphology II. Integrated source properties. Astronomy & Astrophysics 664(2022), article number: A84. (10.1051/0004-6361/202142513)
- Neralwar, K. R. et al. 2022. The SEDIGISM survey: Molecular cloud morphology. Astronomy & Astrophysics 663, article number: A56. (10.1051/0004-6361/202142428)
- Urquhart, J. S. et al. 2022. ATLASGAL - evolutionary trends in high-mass star formation. Monthly Notices of the Royal Astronomical Society 510(3), pp. 3389–3407. (10.1093/mnras/stab3511)
- Colombo, D. et al. 2022. The SEDIGISM survey: the influence of spiral arms on the molecular gas distribution of the inner Milky Way. Astronomy & Astrophysics 658, pp. 1-38., article number: A54. (10.1051/0004-6361/202141287)
- Anderson, M. et al. 2021. An ALMA study of hub-filament systems - I. On the clump mass concentration within the most massive cores. Monthly Notices of the Royal Astronomical Society 508(2), pp. 2964–2978. (10.1093/mnras/stab2674)
- Smith, M. W. L. et al. 2021. The HASHTAG project: The first submillimeter images of the Andromeda Galaxy from the ground.. Astrophysical Journal Supplement Series 257, article number: 52. (10.3847/1538-4365/ac23d0)
- Elia, D. et al. 2021. The Hi-GAL compact source catalogue - II. The 360° catalogue of clump physical properties. Monthly Notices of the Royal Astronomical Society 504(2), pp. 2742–2766. (10.1093/mnras/stab1038)
- Duarte Cabral, A. et al. 2021. The SEDIGISM survey: molecular clouds in the inner galaxy. Monthly Notices of the Royal Astronomical Society 500(3), pp. 3027-3049. (10.1093/mnras/staa2480)
- Urquhart, J. S. et al. 2021. SEDIGISM-ATLASGAL: dense gas fraction and star formation efficiency across the galactic disk. Monthly Notices of the Royal Astronomical Society 500(3), article number: staa2512. (10.1093/mnras/staa2512)
- Eden, D. J. et al. 2021. Characteristic scale of star formation. I. Clump formation efficiency on local scales. Monthly Notices of the Royal Astronomical Society 500(1), pp. 191-210. (10.1093/mnras/staa3188)
- Schuller, F. et al. 2021. The SEDIGISM survey: first data release and overview of the Galactic structure*. Monthly Notices of the Royal Astronomical Society 500(3), article number: staa2369. (10.1093/mnras/staa2369)
- Henshaw, J. D. et al. 2020. Ubiquitous velocity fluctuations throughout the molecular interstellar medium. Nature Astronomy 4, pp. 1064-1071. (10.1038/s41550-020-1126-z)
- Eden, D. J. et al. 2020. CHIMPS2: survey description and 12CO emission in the Galactic centre. Monthly Notices of the Royal Astronomical Society 498(4), pp. 5936-5951. (10.1093/mnras/staa2734)
- Syed, J. et al. 2020. Atomic and molecular gas properties during cloud formation. Astronomy and Astrophysics 642, article number: A68. (10.1051/0004-6361/202038449)
- Wang, Y. et al. 2020. Dense gas in a giant molecular filament. Astronomy and Astrophysics 641, article number: A53. (10.1051/0004-6361/202037928)
- Beuther, H. et al. 2020. Dynamical cloud formation traced by atomic and molecular gas. Astronomy and Astrophysics 638, article number: A44. (10.1051/0004-6361/202037950)
- Mottram, J. C. et al. 2020. From clump to disc scales in W3 IRS4. Astronomy and Astrophysics 636, article number: A118. (10.1051/0004-6361/201834152)
- Li, Z. et al. 2020. The HASHTAG project I. A survey of CO(3–2) emission from the star forming disc of M31. Monthly Notices of the Royal Astronomical Society 492(1), pp. 195-290. (10.1093/mnras/stz3409)
- Wang, Y. et al. 2020. Cloud formation in the atomic and molecular phase: HI self absorption (HISA) towards a giant molecular filament. Astronomy and Astrophysics 634, article number: A139. (10.1051/0004-6361/201935866)
- Pettitt, A. R., Ragan, S. E. and Smith, M. C. 2020. Young stars as tracers of a barred-spiral Milky Way. Monthly Notices of the Royal Astronomical Society 4914(2), pp. 2162-2179. (10.1093/mnras/stz3155)
- Rigby, A. J. et al. 2019. CHIMPS: physical properties of molecular clumps across the inner Galaxy. Astronomy and Astrophysics 632, article number: A58. (10.1051/0004-6361/201935236)
- Clark, P. C., Glover, S. C. O., Ragan, S. E. and Cabral, A. 2019. Tracing the formation of molecular clouds via [CII], [CI] and CO emission. Monthly Notices of the Royal Astronomical Society 486(4), pp. 4622-4637. (10.1093/mnras/stz1119)
- Henshaw, J. D. et al. 2019. ‘The Brick’ is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016. Monthly Notices of the Royal Astronomical Society 485(2), pp. 2457-2485. (10.1093/mnras/stz471)
- Rugel, M. R. et al. 2019. Feedback in W49A diagnosed with radio recombination lines and models. Astronomy and Astrophysics 622, article number: A48. (10.1051/0004-6361/201834068)
- Soler, J. D. et al. 2019. Histogram of oriented gradients: a technique for the study of molecular cloud formation. Astronomy and Astrophysics 622, article number: A166. (10.1051/0004-6361/201834300)
- Rugel, M. et al. 2018. OH absorption in the first quadrant of the Milky Way as seen by THOR. Astronomy and Astrophysics 618, article number: A159. (10.1051/0004-6361/201731872)
- Ahmadi, A. et al. 2018. Core fragmentation and Toomre stability analysis of W3(H20): A case study of the IRAM NOEMA large program CORE. Astronomy and Astrophysics 618(46), article number: A46. (10.1051/0004-6361/201732548)
- Beuther, H. et al. 2018. Fragmentation and disk formation during high-mass star formation: the IRAM NOEMA (Northern Extended Millimeter Array) large program CORE. Astronomy and Astrophysics 617, article number: A100. (10.1051/0004-6361/201833021)
- Ragan, S. E., Moore, T. J. T., Eden, D. J., Hoare, M. G., Urquhart, J. S., Elia, D. and Molinari, S. 2018. The role of spiral arms in Milky Way star formation. Monthly Notices of the Royal Astronomical Society 479(2), pp. 2361-2373. (10.1093/mnras/sty1672)
- Barnes, A. T. et al. 2018. Similar complex kinematics within two massive, filamentary infrared dark clouds?. Monthly Notices of the Royal Astronomical Society 475(4), pp. 5268-5289. (10.1093/mnras/sty173)
- Marsh, K. et al. 2017. Multi-temperature mapping of dust structures throughout the Galactic Plane using the PPMAP tool with Herschel Hi-GAL data. Monthly Notices of the Royal Astronomical Society 471(3), pp. 2730-2742. (10.1093/mnras/stx1723)
- Elia, D. et al. 2017. The Hi-GAL compact source catalogue. I. The physical properties of the clumps in the inner Galaxy (−71.0 ◦ < ` < 67.0◦). Monthly Notices of the Royal Astronomical Society 471(1), pp. 100-143. (10.1093/mnras/stx1357)
- Ragan, S. E., Moore, T. J. T., Eden, D. J., Hoare, M. G., Elia, D. and Molinari, S. 2016. The prevalence of star formation as a function of Galactocentric radius. Monthly Notices of the Royal Astronomical Society 462(3), pp. 3123-3129. (10.1093/mnras/stw1870)
- Beuther, H. et al. 2016. The HI/OH/Recombination line survey of the inner Milky Way (THOR). Survey overview and data release 1. Astronomy and Astrophysics -Berlin then Les Ulis- 595, article number: A32. (10.1051/0004-6361/201629143)
- Marsh, K., Ragan, S., Whitworth, A. P. and Clark, P. 2016. Evidence that widespread star formation may be underway in G0.253+016, 'The Brick'. Monthly Notices of the Royal Astronomical Society 461(1), pp. L16-L20. (10.1093/mnrasl/slw080)
- Lippok, N. et al. 2016. Earliest phases of star formation (EPoS). Dust temperature distributions in isolated starless cores. Astronomy and Astrophysics -Berlin then Les Ulis- 592, article number: A61. (10.1051/0004-6361/201525792)
- Feng, S., Beuther, H., Zhang, Q., Henning, T., Linz, H., Ragan, S. and Smith, R. 2016. Are infrared dark clouds really quiescent?. Astronomy and Astrophysics -Berlin then Les Ulis- 592, article number: A21. (10.1051/0004-6361/201526864)
- Abreu-Vicente, J., Ragan, S., Kainulainen, J., Henning, T., Beuther, H. and Johnston, K. 2016. Giant molecular filaments in the Milky Way II. the fourth Galactic quadrant. Astronomy and Astrophysics 590, article number: A131. (10.1051/0004-6361/201527674)
- Bertram, E., Glover, S., Clark, P., Ragan, S. and Klessen, R. 2016. Synthetic observations of molecular clouds in a galactic centre environment - I. Studying maps of column density and integrated intensity. Monthly Notices of the Royal Astronomical Society 455(4), pp. 3763-3778. (10.1093/mnras/stv2619)
- Beuther, H., Ragan, S. E., Johnston, K., Henning, T., Hacar, A. and Kainulainen, J. T. 2015. Filament fragmentation in high-mass star formation. Astronomy and Astrophysics 584, article number: A67. (10.1051/0004-6361/201527108)
- Walsh, A. et al. 2015. A survey for hydroxyl in the THOR pilot region around W43. Monthly Notices of the Royal Astronomical Society 455(4), pp. 3494-3510. (10.1093/mnras/stv2446)
- Beuther, H. et al. 2015. Hierarchical fragmentation and collapse signatures in a high-mass starless region. Astronomy and Astrophysics 581, article number: A119. (10.1051/0004-6361/201526759)
- Bihr, S. et al. 2015. THOR: The H i, OH, Recombination line survey of the Milky Way. The pilot study: H i observations of the giant molecular cloud W43. Astronomy and Astrophysics 580, article number: A112. (10.1051/0004-6361/201425370)
- Bihr, S. et al. 2015. Kinematic and thermal structure at the onset of high-mass star formation. Astronomy and Astrophysics 579, article number: A51. (10.1051/0004-6361/201321269)
- Ragan, S. E., Henning, T., Beuther, H., Linz, H. and Zahorecz, S. 2015. Fragmentation and kinematics of dense molecular cores in the filamentary infrared-dark cloud G011.11–0.12. Astronomy and Astrophysics 573, article number: A119. (10.1051/0004-6361/201424948)
- Tobin, J. et al. 2015. Characterizing the youngest Herschel-detected protostars. I. envelope structure revealed by CARMA dust continuum observations. Astrophysical Journal 798(2), article number: 128. (10.1088/0004-637X/798/2/128)
- Beuther, H. et al. 2014. Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: cloud formation signatures and carbon gas fractions. Astronomy and Astrophysics 571, article number: A53. (10.1051/0004-6361/201424757)
- Ragan, S. E., Henning, T., Tackenberg, J., Beuther, H., Johnston, K. G., Kainulainen, J. and Linz, H. 2014. Giant molecular filaments in the Milky Way. Astronomy and Astrophysics 568, article number: A73. (10.1051/0004-6361/201423401)
- Johnston, K., Beuther, H., Linz, H., Schmiedeke, A., Ragan, S. and Henning, T. 2014. The dynamics and star-forming potential of the massive Galactic centre cloud G0.253+0.016. Astronomy and Astrophysics 568, article number: A56. (10.1051/0004-6361/201423943)
- Tackenberg, J. et al. 2014. Kinematic structure of massive star-forming regions. I. accretion along filaments. Astronomy and Astrophysics 565, article number: A101. (10.1051/0004-6361/201321555)
- Wang, K. et al. 2014. Hierarchical fragmentation and differential star formation in the Galactic `Snake': infrared dark cloud G11.11-0.12. Monthly Notices of the Royal Astronomical Society 439(4), pp. 3275-3293. (10.1093/mnras/stu127)
- Ragan, S., Henning, T. and Beuther, H. 2013. APEX/SABOCA observations of small-scale structure of infrared-dark clouds I. early evolutionary stages of star-forming cores. Astronomy and Astrophysics 559(Novemb), article number: A79. (10.1051/0004-6361/201321869)
- Kainulainen, J., Ragan, S., Henning, T. and Stutz, A. 2013. High-fidelity view of the structure and fragmentation of the high-mass, filamentary IRDC G11.11-0.12. Astronomy and Astrophysics 557(Septem), article number: A120. (10.1051/0004-6361/201321760)
- Beuther, H. et al. 2013. Fragmentation and dynamical collapse of the starless high-mass star-forming region IRDC 18310-4. Astronomy and Astrophysics 553(May), pp. 115., article number: A115. (10.1051/0004-6361/201220475)
- Clark, P., Glover, S. C. O., Ragan, S., Shetty, R. and Klessen, R. S. 2013. On the temperature structure of the galactic center cloud G0.253+0.016. Astrophysical Journal Letters 768(2), article number: L34. (10.1088/2041-8205/768/2/L34)
- Pitann, J. et al. 2013. G048.66-0.29: physical state of an isolated site of massive star formation. Astrophysical Journal 766(2), article number: 68. (10.1088/0004-637X/766/2/68)
- Launhardt, R. et al. 2013. The Earliest Phases of Star Formation (EPoS): a Herschel key project: the thermal structure of low-mass molecular cloud cores. Astronomy and Astrophysics 551(March), article number: A98. (10.1051/0004-6361/201220477)
- Nielbock, M. et al. 2012. The Earliest Phases of Star formation (EPoS) observed with Herschel: the dust temperature and density distributions of B68. Astronomy and Astrophysics 547(Novemb), article number: A11. (10.1051/0004-6361/201219139)
- Ragan, S. et al. 2012. The Earliest Phases of Star Formation (EPoS): a Herschel key program: the precursors to high-mass stars and clusters. Astronomy and Astrophysics 547(Novemb), article number: A49. (10.1051/0004-6361/201219232)
- Ragan, S., Heitsch, F., Bergin, E. and Wilner, D. 2012. Very large array observations of ammonia in infrared-dark clouds. II. internal kinematics. Astrophysical Journal 746(2), article number: 174. (10.1088/0004-637X/746/2/174)
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Ymchwil
Fy ymchwil: arsylwi ffurfiant sêr Galactig
Mae fy mhrif ddiddordebau ymchwil yn yr amodau sy'n angenrheidiol ar gyfer ffurfio sêr. Rwy'n cymryd rhan mewn nifer o brosiectau gyda llawer o gydweithwyr rhyngwladol. Rwy'n tynnu sylw at y prosiectau rydw i wedi bod yn eu harwain yn ddiweddar. Cysylltwch â mi os oes gennych ddiddordeb neu os hoffech holi am brosiectau posibl!
Ffurfiant seren graddfa alaeth
Mae arolygon awyrennau galactig yn ein galluogi i astudio natur ffurfiant sêr ledled y Llwybr Llaethog dros raddfeydd ciloparsec. Mae Arsyllfa Ofod Herschel wedi cynnal arolwg o'r awyren Llwybr Llaethog gyfan yn y gyfundrefn tonfedd is-goch bell. Mae'r tonfeddi hyn yn cwmpasu brig y dosbarthiad egni ysblennydd o allyriadau thermol o rawn llwch oer. Mae ffynonellau cryno ar y tonfeddi hyn yn cynrychioli'r rhanbarthau yn y Galaxy sydd â'r amodau oer, trwchus sy'n angenrheidiol ar gyfer ffurfio sêr.
Yn Ragan et al. (2016), rydym yn cyflwyno tueddiadau ar raddfa fawr yn y dosbarthiad o wrthrychau sy'n ffurfio sêr a ddatgelwyd gan yr arolwg Hi-GAL. Fel metrig syml sy'n treiddio i fynychder ffurfiant sêr mewn ffynonellau Hi-GAL, rydym yn diffinio ffracsiwn cyfanswm nifer y ffynonellau Hi-GAL gyda chymar 70 μm fel y 'ffracsiwn sy'n ffurfio sêr' neu SFF. Y SFF cymedrig yn y ddisg galactig fewnol (3.1 kpc < RGC < 8.6 kpc) yw 25 y cant. Er gwaethaf pentwr ymddangosiadol o rifau ffynhonnell ar radii sy'n gysylltiedig â breichiau troellog, nid yw'r SFF yn dangos unrhyw wyriadau sylweddol ar y radii hyn, gan nodi nad yw'r breichiau'n effeithio ar gynhyrchiant sêr clumps trwchus naill ai trwy brosesau sbarduno corfforol neu drwy effeithiau ystadegol samplau ffynhonnell fwy sy'n gysylltiedig â'r breichiau. O fewn yr ystod hon o radiws Galactocentric, gwelwn fod y SFF yn dirywio gydag RGC ar gyfradd o −0.026 ± 0.002 y ciloparsec, er gwaethaf y ffracsiwn màs nwy trwchus y gwelwyd ei fod yn gyson yn yr Galaxy fewnol. Mae hyn yn awgrymu y gallai'r SFF fod yn ddibynnol gwan ar un neu fwy o briodweddau ffisegol ar raddfa fawr yr Alaeth, megis meteleg, maes ymbelydredd, pwysau neu gneifio, fel bod is-strwythurau trwchus cymylau moleciwlaidd yn caffael rhai eiddo mewnol a etifeddwyd o'u hamgylchedd.
Ffilamentau enfawr yn y Llwybr Llaethog
Trwy gydol y Llwybr Llaethog, mae cymylau moleciwlaidd fel arfer yn ymddangos yn ffilamentaraidd mewn morffoleg ar yr hyn sy'n ymddangos fel pob graddfa bosibl. Gan ddefnyddio'r cyfoeth o ddata arolwg awyren Galactic, rydym wedi nodi ffilamentau cydlynol cyflymder ar hyd at raddfeydd maint 100-pc. Mae'r darganfyddiad hwn yn ein galluogi i ddechrau cysylltu'r cymylau ffilamentaidd hollbresennol â strwythur Galateg. Yn Ragan et al. (2014 ) rydym yn nodi ac yn nodweddu'r sampl gyntaf o ffilamentau moleciwlaidd enfawr (GMFs) yn y Galaeth. Mae llawer o GMFs wedi'u halinio'n glir â breichiau troellog ond mae rhai yn sgwâr mewn rhanbarthau rhyng-fraich o'r awyren Galateg. Rydyn ni'n gweld bod gan y GMFs yn y breichiau troellog ffracsiwn uwch o'u màs yn y strwythurau dwysaf, fel y'u gelwir yn "clymau". Mae GMFs yn labordy newydd pwysig lle gallwn gael gwell dealltwriaeth o sut mae cwmwl moleciwlaidd a ffurfiant sêr yn dibynnu ar eu hamgylchedd Galasig.
Oeri llinell strwythur cain mewn cymylau tywyll Galactig
Mae sêr yn cael eu geni yn rhanbarthau dwysaf MCs, ond mae'n ymddangos bod y broses yn aneffeithlon iawn, gyda MCs yn trosi dim ond ychydig y cant o'u cyllideb nwy yn sêr fesul amser deinamig. Mae'r prosesau ffisegol sylfaenol sy'n rheoleiddio'r gyfradd ffurfio sêr (SFR) yn yr ISM yn dal i fod yn anhysbys ac yn cael eu dadlau'n boeth, gydag ymgeiswyr yn amrywio o gythrwfl a meysydd magnetig i adborth serol. Mae dadl bellach yn deillio o'r dystiolaeth arsylwadol, er ei bod yn ymddangos bod y rhanbarthau "dwys" yn MCs yng nghymdogaeth yr haul yn esbonio'r cysylltiadau ffurfio sêr galactig a arsylwyd, mae'r un dull yn methu ag esbonio'r SFR tuag at barth moleciwlaidd canolog (CMZ) y Llwybr Llaethog. Y prif reswm dros y ddadl hon yw nad ydym yn dal i ddeall sut mae MCs yn cael eu cydosod a'u dinistrio — y ddwy broses a osododd yn y pen draw yr amserlen y gall cwmwl ffurfio sêr drosti. Y broblem yw bod carbon monocsid (CO), prif olrheiniwr strwythur a dynameg MC, ond yn sensitif i du mewn oer MCs ac nid eu hamenni, ac mae modelau yn dangos y gall CO ffurfio'n gymharol hwyr yn y broses cynulliad. Felly, mae angen tracwyr amgen a all ymchwilio i nwy yn absenoldeb CO - nwy "CO-dark" fel y'u gelwir - i wneud cynnydd pellach wrth ddeall ffurfiad a dinistr MC.
Tracwyr llinell strwythur mân (FSL) megis carbon ïoneiddio ac atomig ([CII] a [CI]) ac ocsigen atomig ([OI]) yw chwiliedydd allweddol camau cynharaf cynulliad cwmwl. Mae'r llinellau hyn yn bwysig am sawl rheswm. Yn gyntaf, gallant olrhain y trosglwyddiad dwysedd isel o nwy atomig i foleciwlaidd sy'n nodi'r ffin o'r ISM cynnes i'r cronfeydd dŵr oer y mae sêr yn ffurfio ynddynt. Yn ail, maent yn brif oeryddion ISM yn ystod y cyfnod pontio hwn, gan ddarparu ffordd i fesur egni'r ISM. Yn olaf, oherwydd gwahanol briodweddau cyffroi'r llinellau, maent yn caniatáu inni wahaniaethu rhwng gwahanol gyfundrefnau tymheredd a dwysedd yn yr ISM.
Yn Beuther, Ragan et al. (2014), rydym yn cynnal astudiaeth beilot o sampl o gymylau moleciwlaidd quiescent mewn tracwyr o bob cam carbon. Datgelodd ein hastudiaeth fod y swyddogion olrhain yn dangos amrywiaeth o ymddygiadau yn dibynnu ar eu hamgylchedd. Mewn un cwmwl (gweler y ffigur) mae'r allyriad [CII] yn dangos arwyddion diddorol o ffurfio cwmwl deinamig, gydag allyriadau cryf ar y naill ochr i'r nwy trwchus a brofir gyda CO. Gallai hyn fod yn ffurfiad cwmwl "wedi'i ddal yn y ddeddf"! Bydd ein harsylwadau SOFIA dilynol o ardal fwy yn ein helpu i ddatgysylltu'r darlun ymhellach... Cadwch tiwnio!
Addysgu
Trefnydd modiwl Technegau Arsylwadol PX2155 mewn Seryddiaeth, modiwl labordy seryddiaeth israddedig ail flwyddyn.
Bywgraffiad
Rwyf wedi bod yn aelod o staff yr Ysgol Ffiseg a Seryddiaeth ers 2016, ac ar hyn o bryd rwy'n Uwch-ddarlithydd ac yn Gyfarwyddwr Astudiaethau Israddedig. Ers ennill fy PhD yn 2009 ym Mhrifysgol Michigan, Ann Arbor, rwyf wedi dal swyddi ymchwil yn Sefydliad Max Planck ar gyfer Seryddiaeth yn Heidelberg, Prifysgol Leeds a Phrifysgol Caerdydd. Dechreuais ar swydd academaidd yn 2018.
Mae fy ymchwil ar gamau cynnar ffurfio sêr, ac rwy'n defnyddio cyfuniad o dechnegau arsylwi a modelu i ddeall pa amodau mewn cymylau moleciwlaidd sy'n angenrheidiol ar gyfer ffurfio sêr, sydd o'r amodau hynny'n hyrwyddo ffurfio sêr màs uchel yn benodol, a beth sy'n achosi ffurfio'r cymylau moleciwlaidd yn y lle cyntaf. Mae ein hymchwil wedi dangos bod y pynciau hyn i gyd yn gysylltiedig, ac yn gysylltiedig â'r amgylchedd ehangach yn y Galaxy hefyd!
Anrhydeddau a dyfarniadau
- 2016 Marie Skłodowska-Curie Research Fellowship (Cardiff University, 2 years funding)
- 2011 Deutsche Forschungsgemeinschaft Grant (Max Planck Institut für Astronomie, 3 years funding)
- 2009 Ralph Baldwin dissertation award (University of Michigan, prize)
- 2007 Spitzer Space Telescope archival research grant (1 year funding)
- 2006 Green Bank Telescope student support grant (1 year funding)
Safleoedd academaidd blaenorol
Academic positions
- 2021 - present: Senior Lecturer, Cardiff University, School of Physics and Astronomy, Cardiff, UK
- 2018 - 2021 : Lecturer, Cardiff University, School of Physics and Astronomy, Cardiff, UK
- 2016 - 2018: Marie Skłodowska-Curie Fellow, Cardiff University, School of Physics and Astronomy, Cardiff, UK
- 2014 - 2016: Postdoctoral Research Assistant, University of Leeds, School of Physics and Astronomy, Leeds, UK
- 2011 - 2014: Deutsche Forschungsgemeinschaft (self-funded) Postdoctoral fellow, Max Planck Insitut für Astronomie, Heidelberg, Germany
- 2010 - 2011: Star and Planet formation postoctoral fellow, Max Planck Institut für Astornomie, Heidelberg, Germany
Education
- 2009: PhD (Astronomy & Astrophysics) University of Michigan, Ann Arbor, MI, USA
- 2003: BSc ( [1] Astronomy, [2] Physics and [3] Mathematics ) Drake University, Des Moines, IA, USA
Pwyllgorau ac adolygu
- Cyfarwyddwr Astudiaethau Israddedig, Ysgol Ffiseg a Seryddiaeth, Prifysgol Caerdydd
- Cadeirydd y Bwrdd Arholi, yr holl raglenni israddedig, Ysgol Ffiseg a Seryddiaeth, Prifysgol Caerdydd
- Aelod o'r pwyllgor Tegwch, Amrywiaeth a Chynhwysiant, Ysgol Ffiseg a Seryddiaeth, Prifysgol Caerdydd
- adolygydd grant, STFC
- Canolwr cyfnodolion, ApJ, A&A, MNRAS
Themâu ymchwil
Arbenigeddau
- Gwyddor data
- Gwyddorau seryddol
- Offeryniaeth seryddol
- Seryddiaeth galactig