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 arcsec T arcsec "$ "$ V (km s-1)! "# arcsec! "# 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, ! Jime%nez-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 ß 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! &IRAM_beam + &source = &IRAM✪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! &IRAM_beam + &source = &IRAM✪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 2 -1 0 0 CH CHO A CH CHO E 3 3 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 2 -1 0 0 CH CHO A CH CHO E 3 3 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! .