unraveling the mysteries of complex interstellar organic chemistry using hifi line surveys susanna...
TRANSCRIPT
Unraveling the Mysteries of Complex Interstellar Organic Chemistry Using
HIFI Line Surveys
Susanna L. Widicus Weaver, Mary L. Radhuber, Jay A. Kroll, Brett A. McGuire, and Jacob C.
LaasDepartment of Chemistry, Emory University
Darek C. LisCalifornia Institute of Technology
Eric HerbstOhio State University
^ Observational Spectral
Why Molecular Line Surveys?
Our Goals:• Conduct surveys for many different types of sources• Achieve high spectral sensitivity (for new molecule
ID)• Obtain full picture of chemical, physical conditions
for each source• Compare results to astrochemical models
• New astrochemical models attempt to explain formation of complex organics
• Models require complete chemical, physical picture for input/comparison
• Physical parameters, abundances often educated guesses
• Few surveys access differing chemical, physical environments
Garrod, Widicus Weaver, & Herbst, ApJ 682, 2008
Tracing Chemical Pathways in the ISMH2O + hn OH + H
H2 + O
CH3OH + hn CH3 + OHCH3O + HCH2OH + H
NH3 + hn NH2 + H
H2CO + hn HCO + H
HCO + CH2OH HOCH2CHO (glycolaldehyde)HCO + CH3O CH3OCHO (methyl formate)HCO + OH HCOOH (formic acid)HCO + CH3 CH3CHO (acetaldehyde)HCO + NH2 H2NCHO (formamide)CH3 + CH3O CH3OCH3 (dimethyl ether)CH3 + NH2 CH3NH2 (methyl amine)CH3 + CH2OH CH3CH2OH (ethanol)CH2OH + CH2OH HOCH2CH2OH (ethylene glycol)
hn
H2O, CO, CH3OH, NH3 , H2CO Ice mantle
Garrod, Widicus Weaver, & Herbst, ApJ 682, 2008
CSO Orion Spectrum
3018 >3-s lines observed
59% of the lines are unassigned!
See talk FA05 (Radhuber et al.) for more information.
Results of Spectral Analysis
Residual = incomplete modeling of complex lineshapes + unassigned lines of known molecules + very weak lines from COMs
CSO Line Surveys
Full surveys complete for 8 sources, partial surveys complete for 5 more.
CH3OH HCOOCH3
& CH3OHCH3OCH3 CH3OH
& CH3CNCH3OH
Ta*
(K)
HCOOCH3
THz Observational Astronomy
480 GHz -1.2 THz
1.4 – 1.9 THz
Herschel Space
Observatory
Launched in 2009
Stratospheric Observatory for
Infrared AstronomyScience observations began
in 2010500 GHz – 2.1 THz
Atacama Large Millimeter Array
Early science observations to begin in 201180 GHz – 950 GHz
ESO/José Francisco Salgado
ESA / AOES Medialab background: HST, NASA/ ESA/ STScI
NASA / DLR
Upcoming Herschel Observations
The Importance of Follow-Up Imaging Studies
Friedel and Widicus Weaver, in preparation.
Orion-KL l = 3 mm continuum observations with CARMA
Revealing Chemistry Through Imaging
Different COMs have very different spatial distributions.
Neill et al., J. Phys. Chem., in press.
CARMA+
MF1
Methanol Formic acid Dimethyl ether
Friedel and Widicus Weaver, CARMA, 2008NRAO EVLA Demonstration 2009
Comparison of Methyl Formate in Orion-KL to other COMs
http://amandabauer.blogspot.com/2009/08/carma-telescopes.html
Proposed CARMA Observations
CSO Survey of Orion-KLRMS = 30 mK
Integration Time ~ 4 Nights
Full ALMA Capability Similar coverage on Orion-KL
RMS = 30 mKIntegration Time ~ 1 Minute
OVRO Survey of Orion-KLRMS = 150 mK
Integration Time ~ 27 Nights
eVLA Demonstration ScienceImage courtesy of NRAO https://science.nrao.edu/facilities/evla/earlyscience/demoscience
Blake et al. 1987, ApJ 315, 621
Radhuber et al., in preparation.
ALMA Changes Everything
• CSO surveys at 230 GHz8 GHz spectrometer = More sources in less time
• HIFI line surveys at 680 GHz & 1.2 THzOT-1 observations 2011/2012OT-2 proposals due September 15
• CARMA imaging at 230 GHzProposal review this week
• ALMA imaging at 680 GHzCycle-0 proposals due June 30
• Comparison to modelsID molecules that trace gas-phase or grain-surface
chemistryCompare relative abundances of isomers,
conformers
• Future observationsCSO 345 GHz receiver + 8 GHz spectrometerSOFIA
Future Work
http://www.nasa.gov/centers/jpl/images/content/391019main_herschel-b-20091002-full.jpg
AcknowledgementsThe Widicus Weaver Group:Brian Hays, Le Zhong, Cate Levey, Jay Kroll, Jake Laas, Brett McGuire, Mary Radhuber, Brandon Carroll, Sophie Lang, Anne Carroll
CSO/Caltech: Jonas Zmuidzinas, Tom Phillips, Geoffrey Blake, CSO Staff & TAC
HIFI/HEXOS: Ted Bergin, Nathan Crockett, Claudia Comito, Peter Schilke, Martin Emprechtinger, Steve Lord
UIUC/CARMA: Doug Friedel
NRAO/ALMA: Anthony Remijan