Browsing by Author "Aalto, Susanne"

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    Extreme CO Isotopic Abundances in the ULIRG IRAS 13120-5453: An Extremely Young Starburst or Top-heavy Initial Mass Function
    (IOP PUBLISHING LTD, 2017) Sliwa, Kazimierz; Wilson, Christine D.; Aalto, Susanne; Privon, George C.
    We present ALMA (CO)-C-12 (J = 1-0, 3-2 and 6-5), (CO)-C-13(J = 1-0), and (CO)-O-18 (J = 1-0) observations of the local ultraluminous infrared galaxy (ULIRG) IRAS. 13120-5453. The morphologies of the three isotopic species differ, as (CO)-C-13 shows a hole in emission toward the center. We measure integrated brightness temperature line ratios of (CO)-C-12/(CO)-C-13 >= 60 (exceeding 200) and (CO)-C-13/(CO)-O-18 <= 1 in the central region. Assuming optical thin emission, (CO)-O-18 is more abundant than (CO)-C-13 in several regions. The abundances within the central 500 pc are consistent with the enrichment of the interstellar medium via a young starburst(<7 Myr), a top-heavy initial mass function, or a combination of both.
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    Fast, Collimated Outflow in the Western Nucleus of Arp 220
    (2018) Barcos-Munoz, Loreto; Aalto, Susanne; Thompson, Todd A.; Sakamoto, Kazushi; Martin, Sergio; Leroy, Adam K.; Privon, George C.; Evans, Aaron S.; Kepley, Amanda
    We present the first spatially and spectrally resolved image of the molecular outflow in the western nucleus of Arp 220. The outflow, seen in HCN (1-0) by the Atacama Large millimeter/sub-millimeter Array, is compact and collimated, with an extension less than or similar to 120 pc. Bipolar morphology emerges along the minor axis of the disk, with redshifted and blueshifted components reaching a maximum inclination-corrected velocity of similar to +/- 840 km s(-1). The outflow is also seen in CO and continuum emission, the latter implying that it carries significant dust. We estimate a total mass in the outflow of >= 10(6) M-circle dot, a dynamical time of similar to 10(5) yr, and mass outflow rates of >= 55 M-circle dot yr(-1) and >= 15 M-circle dot yr(-1) for the northern and southern lobes, respectively. Possible driving mechanisms include supernovae energy and momentum transfer, radiation pressure feedback, and a central AGN. The latter could explain the collimated morphology of the HCN outflow; however, we need more complex theoretical models, including contributions from supernovae and AGN, to pinpoint the driving mechanism of this outflow.