Héctor G. Arce Yale University Image Credit: ESO/ALMA/H. Arce/ B. Reipurth Shocks and Molecules in Protostellar Outflows

Molecules in Space part of recycling of ISM Images courtesy of NRAO/AUI

Importance of multi-line observations in star-forming region / ISM Needed to constraining chemical models. Detection and identification of complex molecules in different environment (e.g., cold clouds, PDRs, diffuse clouds, etc.) provides critical information for understanding the possible formation (and destruction) pathways of these molecules Some of the complex molecules found in the ISM are large organic molecules, thought to be important for the formation of molecules important for life. It is possible that chemical processes in the interstellar medium provide the essential material that allowed the emergence of life. Link to astrobiology Chemistry Astrophysics Can be used to study evolution of clouds and the star formation process. Different species trace different density and “kinematic” regimes

Zooming in on star-forming core Figure from Herbst & van Dishoeck (2009)

Shocks trigger physical processes (e.g., ice sputtering, grain destruction) and chemical reactions (i.e., warm/high-temp. gas-phase chemistry) not present in quiescent gas, affecting the chemical abundance of different molecules in cloud, and helping in formation of other molecules (e.g., Bachiller et al. 2001; Herbst & van Dishoeck 2009). Can use shocks to probe dust composition and warm chemistry probably existent close to forming star/planets disk envelope outflow Protostellar outflows: great lab for studying shock physics and chemistry Images courtesy of NRAO/AUI

Protostellar Jets and Molecular Outflow 1 pc L1551 Optical emission (shock excited atomic lines) Contours: CO outflow emission (  ~ mm ) Bally et al.; Stojimirovic et al. (2006) Looney et al. (2007); Bachiller et al. (2001) (both trace recently shocked gas) low-J CO (mostly) trace entrained gas IR emission (mostly shock-heated H 2 lines) L pc Zinnecker et al. (1998) HH 212 IR image 10 4 AU

IRAC 2 (4.5µm) Outflows in Protostellar Cluster Green image: IRAC 2 (4.5µm) emission (Gutermuth et al. 2008) NGC 1333 protostellar cluster Red and Blue contours: Red- and blue-shifted CO outflow using CARMA (Plunkett et al. 2013) Example: NGC 1333

Water in outflow dominated by: High-temperature gas-phase chemistry: O + H 2 —> OH +H OH + H 2 —> H 2 O + H Ice sputtering: H 2 O (solid) —> H 2 O (gas) Possible path for increase of HCO + in outflows 1) Release of water and CO ice from dust due to shock heating: CO (solid) —> CO (gas) H 2 O (solid) —> H 2 O (gas) 2) CO may be photo dissociated in shock, and C can be photoionized hv + CO —> C + O hv + C —> C + + e - 3) Reaction of C + with water results in HCO+ C + + H 2 O —> HCO + + H Green image: IRAC 2 (4.5µm) emission (Gutermuth et al. 2008) Red: redshifted H 2 O ( ) Blue: blueshifted H 2 O ( ) [~ 557 GHz] Orange: redshifted HCO + (1-0) Cyan: blueshifted HCO + (1-0) [~ 89 GHz] Water and HCO + in outflows Water typically traces recently shocked gas H 2 O observed with Herschel (Arce et al., in prep.), HCO+ observed with CARMA (CLASSy data, Mundy et al., in prep.) SVS 13 IRAS 2A NGC 1333 protostellar cluster

Multi-line observations of SVS 13 (HH7-11) outflow different species and shock chemistry can help understand outflow entrainment mechanism spectrum towards source position CO (1-0) HCO + (1-0) H 2 O ( ) CO (1-0) outflow CO (1-0) & HCO + (1-0) CO (1-0) & H 2 O ( ) HCO + (1-0) & H 2 O ( ) CO from Plunkett et al. (2013) HCO + from CLASSy (Mundy et al., in prep.) H 2 O observed with Herschel (Arce et al., in prep.)

HCN In warm temperatures HCN is produced more than HNC HCN in outflows HCN seems to trace young shocks HCN observed with CARMA (CLASSy data, Mundy et al., in prep.) Magenta: redshifted HCN(1-0) Light blue: blueshifted HCN(1-0) [~ 89 GHz] Green image: IRAC 2 (4.5µm) emission (Gutermuth et al. 2008)

Comparing distribution and kinematics HCN(1-0) + HCO + (1-0) H 2 O ( ) + HCO + (1-0) H 2 O ( )HCO + (1-0)HCN(1-0) spectra at peak position

Comparing distribution and kinematics in IRAS 2A CO (1-0) & HCO + (1-0) CO (1-0) & HNC (1-0) distribution using integrated intensity maps kinematics using position-velocity diagrams CO (1-0) HCO + (1-0) HCN (1-0) CO from Plunkett et al. (2013) HCN and HCO + from CLASSy (Mundy et al., in prep.) p-v cut

Complex Organic Molecules (COMs) in outflows IRAM 30m observations of IRAS 2A-E1 Arce et al., in prep. NGC1333-IRAS2A redshifted

Looney et al. (2007) Arce et al. (2008); see also Yamaguchi et al. (2012) Arce et al., in prep. Arce et al., in prep. B1 B2 L1157 L1157-B1 L1157-B2 COMs in outflows: L1157 IRAM 30m observations of L1157 B1 and B2  shock ~ 10 3 yr indicates that complex species formed in the surface of grains and were then ejected from the grain mantles by the shock. Formation of COMs on grains in low-mass star forming regions must be relatively efficient.

Commonly detected COMs: HCOOCH 3, HCOOH, C 2 H 5 OH, CH 3 CHO Detected Complex Organic Molecules in Outflows Other common COMs: CH 3 OCH 3, CH 3 CN,C 3 H 2 Less common COMs: HCCCH, NH 2 CHO, CH 3 CCH E1 * * C 2 H 5 OH X + + HCOOCH 3 CH 3 CHO CH 3 OCH 3 Low Mass High Mass Abundances of most common COMs (preliminary results) Comparing abundances with other sources of COMs Figure from Öberg et al. (2011) + some data from Arce et al. in prep. COMs in different SF environments seem to have formed in similar way

Reaction scheme of CH 3 OH-based ice photochemistry Öberg et al. (2010) = HCO-bearing complex species = only produced abundantly at lukewarm temp. (> 30 K in lab) Molecules (and abundances) consistent with formation on (CO-dominated) ice surface aided by UV and CR Evolution of ices in star-forming core = CO-dominated ice = H 2 O-dominated ice COMs found in outflows likely formed on dust ice surface Commonly detected COMs: HCOOCH 3, HCOOH, C 2 H 5 OH, CH 3 CHO Other common COMs: CH 3 OCH 3, CH 3 CN,C 3 H 2 Less common COMs: HCCCH, NH 2 CHO, CH 3 CCH

Looney et al. (2007) L1157 Benedettini et al. (2013) PdBI observations of L1157 B1 Future ALMA observations Investigate spatial distribution of COMs with respect to other species B1 ~3000 AU

COMs in solar system comets Plot from Bockelée-Morvan et al. (2000) with additional data from Arce et al. (2008) (comparing comet Hale-Bopp with ISM) The abundance ratios in the cometary ices present strong similarities with those measured in ISM (i.e., hot cores, outflows, etc.). This seems to be consistent with formation of the cometary molecules in the protosolar cloud, or at least in processes very similar to those met in the interstellar medium. Further comparison should be made with observations of COMs in inner circumstellar envelope and disks with ALMA Image courtesy of NRAO/AUI

Summary Outflows trigger chemical enrichment in the surrounding gaseous environment - Herschel shows H 2 O abundant in recently shocked regions - CARMA data show overabundance of HCO+ and HCN towards outflows - Multi-line observations help constrain shock models and entrainment mechanism Detection of Complex Organic Molecules in young protostellar outflows - Formation of complex molecules on grain is relatively efficient - Abundances seem to be consistent with formation on UV-exposed CO-dominated ice Results indicate that radiation from protostar is not sole mechanism that can liberate COMs onto gas phase near low-mass protostars - impact from outflow/shocks needs to be considered when studying COMs in circumstellar environment