The Distribution of Astronomical

Aldehydes – The Case for Extended Emission

of Acetaldehyde (CH3CHO).Andrew Burkhardt1,2

Ryan Loomis3, Niklaus Dollhopf1,2, Joanna Corby1,2, Anthony Remijan2

1 University of Virginia

2 NRAO

3 Harvard University

Distribution Implies Formation Routes

Extended vs compact emissionHot vs coldGas vs grain formation

Distribution of different transitions can map out different components of molecular transitionsALMA gives us unprecedented capabilities to study

the spatial distribution with incredible sensitivity

Why Aldehydes?

Formaldehyde was the first organic polyatomic molecule detected in the ISM by Snyder et al. (1969)

Formaldehydes and other simple aldehydes can, through formose reactions, produce sugars and ultimately ribose, the basis of RNA

Aldehydes as seen in Sgr B2(N)

In Sgr B2(N), observed to have extended emission and potentially no compact emission (Chengalur and Kanekar, 2003)

The extended distribution is also inferred for other aldehydes toward Sgr B2(N) including glycolaldehyde (Hollis et al., ApJ, 2001) and propynal.

It is thought that there is an underlying formation mechanism to produce aldehydes in cold regions

Is this unique to Sgr B2(N) or should we see this in other massive star forming regions (Orion KL)?

Acetaldehyde (CH3CHO)

Has been detected in numerous sources, and multiple times in Orion KL with single dish (Turner 1989, 1991, PRIMOS survey at cv.nrao.edu/~aremijan/PRIMOS)

Conflicting results from interferometric dataLiu 2005 reports spatially coincident with

HCOOH with BIMAFriedel 2008 reports a non-detection of

HCOOH and CH3CHO with CARMA, implying extended emission is resolved out

Multiple Components

Turner (1989, 1981) & Nummelin et al (2000) observed highly elevated b-type transitions in Orion KL compared to a-type, proposing radiative pumping of the low-lying vibrational states

The ‘a’ dipole moment is 2.5 times larger than the ‘b’. In a given frequency range, the ‘b’-type transitions will have higher upper-state transitions

Postulate that there could be multiple components (cold extended and hot compact).

Need to map over multiple transitions and spatial scales

Orion KL Structure

Friedel et al., 2008

ALMA/CARMA Observations

Science Verification Band-6 Survey data of Orion KL 20x1.9 GHz spectral windows each with ~3800

channelsHigh resolution/sensitivityCan map out all relevant transitionsSee TF04 by Remijan for more information

CARMA B/E Array7x62 MHz narrow band and 1x500 MHz wideband

windowsE Array (Max baseline 240 m)B Array (Max baseline 2395 m)

a-type transitions

a-type transitions

Emission is seen as compact

Both along the compact ridge and surrounding (but not in) the hot core

b-type transitions

More compact emission, surround the hot core and at the compact ridge

CARMA E-Array

Low-energy, cold extended emission (a-type transition)

SW region seen in extended emission (E Array)

Not seen in SV data due to loss of sensitivity in beam

CARMA E-Array

b-type transitions (seen as compact in SV) unresolved in E-Array

CARMA B-Array

Cold, extended emission is resolved out

Very weak compact emission detected for these low energy transitions

t-HCOOH vs CH3CHO

As predicted by Liu, cold extended emission of t-HCOOH is cospatial with CH3CHO, excluding SW region

CH3OH vs CH3CHO

CH3OH and CH3OH are cospatial for the compact emission seen in SV data, with agreement with Friedel et al. (2011,2012)

Unlike CH3CHO, CH3OH is abundant in the hot core due to not being fully destroyed during gas-grain warm up

CH3OH vs CH3CHO

In addition to compact emission, CARMA E-Array detected cold- extended emission

Futhermore, the SW region seen in CH3CHO are found for CH3OH emission

Conclusions

ALMA:

High-J transitions occur in compact emission

CH3CHO is destroyed in hot core during grain-warm up

CARMA:

E-Array detects extended, cold emission

B-Array detects limited compact emission surrounding the hot core

Thanks

National Radio Astronomy Observatory Summer Student Program

ALMA Science Verification Team

Virginia Space Grant Consortium

Collaborators and Peers