Prevalence of Complex Organic Molecules in Prestellar Cores Within the Taurus Star Forming Region

Samantha Scibelli 3rd year Graduate Student and NSF Fellow Advised by Dr. Yancy Shirley

Steward Observatory, University of Arizona

Celebrating The First 40 Years Of Alexander Tielens’ Contribution To Science: The Physics And Chemistry Of The ISM Palais des Papes in Avignon, France. 2nd – 6th September 2019 Origins of Complex Molecules

+ - Gas: CH3OH2 + e à CH3OH + H only 3% yield … too SLOW (Geppert et al. 2006) Photo- Gas-phase Chemistry desorption d Ion-molecule Reactions UV/XUV à COM abundances several Silicate or Irradiation / of orders of magnitude lower than Carbonaceous & Cosmic observed grain Rays (Charnley & Tielens 1992) Chemical reactions How do complex organics form in Ion- radiation (Burke & Brown 2010) cold (10 K), UV- shielded environments? Origins of Complex Molecules

Solid: CO + H à HCO + H à H2CO + H à CH3O + H à CH3OH Chemical Chemical Reactive desorption Desorption d Neutral-Neutral Silicate or / Carbonaceous reactions of radicals grain

Chemical Models predict reactions abundances Ion- radiation (Minissale et al. 2016, which we can Vasyunin et al. 2017) constrain! COMs in Prestellar Cores

B68

Methanol When, where CH3OH and how are these molecules forming in Acetaldehyde prestellar CH3CHO cores?

Dimethyl Birthplace of low-mass stars Ether (M ≤ a few M¤) CH₃OCH₃ 4 5 -3 Dense (10 - 10 cm ) & cold (≤ 10K ) COMs in Prestellar Cores (K) mb T Δδ arcsec Δδ arcsec

V (km s-1) Δα arcsec Δα arcsec LSR L1498 L1517B Tafalla et al. 2006

TMC-1

CH3CHO CH3CHO (5-4) A (5-4) E

CH3OH (20,2 - 10,1 A ) C34S (J = 2 − 1)

Soma et al. 2015 L1689B Bacmann et al. 2012 COMs in Prestellar Cores

Methyl Formate L1544 Well Studied Very Methyl Isocyanide Evolved Core

Vinyl cyanide Ethynl Acetaldehyde isocyanide

(Bizzocchi et al. 2014, Jiménez-Serra et al. 2016, COMs observed in only a few (< 10) well- Spezzano et al. 2017, Chacón-Tanarro et al. 2017, known dense and evolved prestellar cores Chacón-Tanarro et al. 2019) L1521E: A “Young” Core

• Very low CO depletion 500 µm • No indication in kinematics of collapse • “Early-time” molecules (CCS, etc.) peak on core + • “Late-time” molecules (NH3, N2H ) very weak • Weak deuteration (chemically young)

Makiwa et al. 2004 CO Depletion

Tafalla et al. 2004 L1521E COM Line Survey

Arizona Radio Observatory (ARO) 12m dish COM Line Survey

Scibelli et al., in Prep L1521E COM Line Survey

Acetaldehyde (CH3CHO) Detections

Scibelli et al., in Prep L1521E COM Line Survey

Estimating true column density from source size: CH3OH 2 2 2 θIRAM_beam + θsource = θIRAM✪source Underestimates column density by factor of ~2.6 Nagy et al. 2019

Scibelli et al., in Prep L1521E COM Line Survey

Estimating true column density from source size: CH3OH 2 2 2 θIRAM_beam + θsource = θIRAM✪source Underestimates column density by factor of ~2.6 Nagy et al. 2019

Need for high resolution maps of COMs to lower systematic source size error

Scibelli et al., in Prep L1521E COM Line Survey

Dimethyl ether (CH3OCH3) & Vinyl Cyanide (CH2CHCN)

Organics Prevalent in L1521E! What about in a more representative sample of cores? Scibelli et al., in Prep Survey of Starless and Prestellar Cores in Taurus

B7 Taurus Molecular Cloud L1495-B218 2 4 CH3OH Beam radius 31’’ 5

B218 39 B10 7 6 11 8 10 9 37 12 15 B216 13 17 16 14 36 B213 B211

DEC (J2000) 35 32 30 20 27 2624 22 H2 Map 33 31 Marsh et al. 2016, Palmeirim et al. 2013 29 28 21

RA (J2000)

Conducted a large-sample systematic survey of 31 prestellar cores selected from NH3 mapping results (Seo et al. 2015) in the Taurus Star Forming region Scibelli et al., submitted to ApJ ARO 12m Observing

Detected methanol (CH3OH) in 100% of the cores targeted!

Scibelli et al., submitted to ApJ ARO 12m Observing

Detected methanol (CH3OH) in 100% of the cores targeted!

+ CH3OH A 20-10 CH3CHO A CH3CHO E Eu/k = 7 K! 5(0,5)-4(0.4) 5(0,5)-4(0.4) CH3OH E 2-1-1-1 Eu/k = 13.8 K! Eu/k = 13.9 K! Eu/k = 13 K!

CH3OH E 20-10

Eu/k = 20K!

Scibelli et al., submitted to ApJ ARO 12m Observing

Detected acetaldehyde (CH3CHO) in 68% of the cores targeted!

Scibelli et al., submitted to ApJ ARO 12m Observing

Detected acetaldehyde (CH3CHO) in 68% of the cores targeted!

+ CH3OH A 20-10 CH3CHO A CH3CHO E Eu/k = 7 K! 5(0,5)-4(0.4) 5(0,5)-4(0.4) CH3OH E 2-1-1-1 Eu/k = 13.8 K! Eu/k = 13.9 K! Eu/k = 13 K!

CH3OH E 20-10

Eu/k = 20K!

Scibelli et al., submitted to ApJ ARO 12m Observing

84 GHz CH3CHO 2-1 transition (Eup = 5 K) detected in 6 of the 21 cores for which the 96 GHz CH3CHO 5-4 transition was detected in

(K) mb T

Velocity (km/s) Scibelli et al., submitted to ApJ Constraining Column Densities and Abundances

CH3CHO: CTEX Method

Scibelli et al., submitted to ApJ Constraining Column Densities and Abundances

CH3CHO: CTEX Method

For Total Sample: N range: 1.2-5.8 +/- 0.068 – 0.035 (1012 cm−2 ) Tex range: 3.06-5.39 -/+ 0.13 – 0.28 (K) Scibelli et al., submitted to ApJ Constraining Column Densities and Abundances

CH3CHO: CTEX Method CH3OH: RADEX Method

For Total Sample: N range: 1.2-5.8 +/- 0.068 – 0.035 (1012 cm−2 ) Tex range: 3.06-5.39 -/+ 0.13 – 0.28 (K) Scibelli et al., submitted to ApJ Constraining Column Densities and Abundances

CH3CHO: CTEX Method CH3OH: RADEX Method

For Total Sample:

For Total Sample: N range: 0.26 – 1.68 N range: +/- 0.023 - 0.26 13 −2 1.2-5.8 (10 cm ) +/- 0.068 – 0.035 Tex range: 6.79 – 8.66 12 −2 (10 cm ) +/- 0.005 – 0.025 (K) Tex range: 3.06-5.39 -/+ 0.13 – 0.28 (K) Scibelli et al., submitted to ApJ Core Abundances

Scibelli et al., submitted to ApJ Methanol Abundances

Scibelli et al., submitted to ApJ ARO 12m OTF Mapping

Mapping helps us understand the distribution of methanol along the ﬁlaments

CH3OH detected at as low as Av ~ 3-4 mag!

Uncovering velocity structure in CH3OH which is tracing large-scale motions Scibelli et al., submitted to ApJ ARO 12m OTF Mapping

Mapping helps us understand the distribution of methanol along the ﬁlaments

CH3OH detected at as low as Av ~ 3-4 mag!

Core 21

Uncovering velocity Hacar et al. 2013 structure in CH3OH which is tracing large-scale motions Scibelli et al., submitted to ApJ Methanol Abundance Maps

Scibelli et al., submitted to ApJ Deuterated Methanol: Survey of B10 Region

• 75 % Detection Rate! • Deuteration fraction on average ~ 10% for reasonable excitation temperatures (> 4K)

B10 “Less-Evolved” Region Ambrose et al. in prep Next: Vinyl Cyanide Survey

4 Taurus Molecular Cloud L1495-B218 2 L1521E 6 5 7 11 39 8 37 9 10 15 12 13 17 16 14 36 35 30 32 H Map 27 26 22 20 2 33 21 31 24 Marsh et al. 2016, Palmeirim et al. 2013 29 28 Image: SDSS9

Lines Targeted (simultaneously):

Vinyl Cyanide: CH2CHCN 80,8 – 70,7 (75.6 GHz) Vinyl Cyanide: CH2CHCN 81,8 – 71,7 (73.98 GHz) Ethyl Cyanide: CH3CH2CN 81,8 – 71,7 (73.35 GHz) Methyl Cyanide: CH3CN 40 – 33 (73.59 GHz) Important Takeaways

1. The COMs acetaldehyde, dimethyl Ether and vinyl Cyanide have been detected in young core L1521E! 2. We have observed methanol in 100% of the 31 Taurus cores targeted and acetaldehyde in 68%! ² One of the ﬁrst survey’s to target a large, homogenous sample of cores, warranting a robust comparison between cores of similar environmental conditions 3. Abundance measurements of COMs will provide constraints for astrochemical models Complex Organics are forming early and often in prestellar cores! Important Takeaways

1. The COMs acetaldehyde, dimethyl Ether and vinylThanks Cyanide Xander have ! been detected in young core L1521E! 2. We have observed methanol in 100% of the 31 Taurus cores targeted and acetaldehyde in 68%! ² One of the ﬁrst survey’s to target a large, homogenous sample of cores, warranting a robust comparison between cores of similar environmental conditions 3. Abundance measurements of COMs will provide constraints for astrochemical models Complex Organics are forming early and often in prestellar cores!