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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20210617T103000
DTEND;TZID=Atlantic/Canary:20210617T113000
UID:iactalks-1487
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/1487
CREATED:2021-06-17T10:30:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Photoionized Herbig-Haro objects in the Orion Nebula. Laboratories 
 to better understand ionized nebulae.
DESCRIPTION:Photoionized Herbig-Haro objects in the Orion Nebula. Laborator
 ies to better understand ionized nebulae.\nJosé Eduardo Méndez Delgado\n
 \nWe present some results on a project based on high-resolution UVES@
 VLT spectroscopy and HST imaging of photoionized Herbig-Haro (HH) obj
 ects in the Orion Nebula. We study physical conditions, chemical abundance
 s and other properties such as proper motions and the origin of the drivin
 g jets. Our study will include at least 9 HH objets, of which we will focu
 s on HH529II, HH529III and HH204 in this talk. Our data allow us to separa
 te the spectrum of the outflows from the main nebular emission, studying e
 ach object with an unprecedented detail. The HHs are located at different 
 distances from the main ionization source of the Orion Nebula, with differ
 ent ionization/physical conditions and flow velocities. In all objects, th
 e electronic density (ne) is substantially higher than in the surrounding 
 Orion Nebula, while the electronic temperature (Te) is maintained under ph
 otoionization equilibrium for the most abundant ion stages. In HH204 we ob
 serve a Te([OIII]) gradient due to the contribution of [OIII] emission fro
 m the cooling layer behind the bow shock, which is also detected in the HS
 T imaging. The ionization degree of the gas in the different HH objects is
  very different, allowing us to determine the chemical composition of the 
 Orion Nebula under both ionization conditions, avoiding the use of ionizat
 ion correction factors (ICFs) for many elements. HH204 shows an abundance 
 discrepancy  -the difference between abundances derived from recombin
 ation and collisionally excited lines- thas is actually zero. We find dire
 ct evidence of dust destruction in the bow shock in all objects. This incr
 eases the gaseous abundances of Fe, Ni and Cr with respect to the Orion Ne
 bula ones. We show that a failure to resolve the different kinematic compo
 nents -as in a low spectral resolution spectrum- can lead to significant e
 rror in the determination of chemical abundances -40% underestimate of O i
 n the case of HH204-, mainly due to incorrect estimation of the electron d
 ensity.
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