Interstellar Carbodiimide (HNCNH) - A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features

In this work, we identify carbodiimide (HNCNH), which is an isomer of the well-known interstellar species cyanamide (NH2CN), in weak maser emission, using data from the GBT PRIMOS survey toward Sgr B2(N). All spectral lines observed are in emission and have energy levels in excess of 170 K, indicating that the molecule likely resides in relatively hot gas that characterizes the denser regions of this star forming region. The anticipated abundance of this molecule from ice mantle experiments is ~10% of the abundance of NH2CN, which in Sgr B2(N) corresponds to ~2 x 10^13 cm-2. Such an abundance results in transition intensities well below the detection limit of any current astronomical facility and, as such, HNCNH could only be detected by those transitions which are amplified by masing.Comment: Accepted in The Astrophysical Journal Letters, 13 pages, 2 figures, generated using AAS LaTeX Macros v 5.

CSO and CARMA Observations of L1157. I. A Deep Search for Hydroxylamine (NH2_2OH)

A deep search for the potential glycine precursor hydroxylamine (NH$_2$OH) using the Caltech Submillimeter Observatory (CSO) at $\lambda = 1.3$ mm and the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at $\lambda = 3$ mm is presented toward the molecular outflow L1157, targeting the B1 and B2 shocked regions. We report non-detections of NH$_2$OH in both sources. We a perform non-LTE analysis of CH$_3$OH observed in our CSO spectra to derive kinetic temperatures and densities in the shocked regions. Using these parameters, we derive upper limit column densities of NH$_2$OH of $\leq1.4 \times 10^{13}$~cm$^{-2}$ and $\leq1.5 \times 10^{13}$~cm$^{-2}$ toward the B1 and B2 shocks, respectively, and upper limit relative abundances of $N_{NH_2OH}/N_{H_2} \leq1.4 \times 10^{-8}$ and $\leq1.5 \times 10^{-8}$, respectively.Comment: Accepted in the Astrophysical Journa

CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow

L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000 years ago, respectively. Prior to these shock events, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse, evidenced by prior observations of SiO and multiple grain mantle species commonly associated with shocks. Grain species, such as OCS, CH3OH, and HNCO, all peak at different positions relative to species that are preferably formed in higher velocity shocks or repeatedly-shocked material, such as SiO and HCN. Here, we present high spatial resolution (~3") maps of CH3OH, HNCO, HCN, and HCO+ in the southern portion of the outflow containing B1 and B2, as observed with CARMA. The HNCO maps are the first interferometric observations of this species in L1157. The maps show distinct differences in the chemistry within the various shocked regions in L1157B. This is further supported through constraints of the molecular abundances using the non-LTE code RADEX (Van der Tak et al. 2007). We find the east/west chemical differentiation in C2 may be explained by the contrast of the shock's interaction with either cold, pristine material or warm, previously-shocked gas, as seen in enhanced HCN abundances. In addition, the enhancement of the HNCO abundance toward the the older shock, B2, suggests the importance of high-temperature O-chemistry in shocked regions.Comment: Accepted for publication in the Astrophysical Journa

CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow

L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000 years ago, respectively. Prior to these shock events, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse, evidenced by prior observations of SiO and multiple grain mantle species commonly associated with shocks. Grain species, such as OCS, CH_3OH, and HNCO, all peak at different positions relative to species that are preferably formed in higher-velocity shocks or repeatedly shocked material, such as SiO and HCN. Here, we present high spatial resolution (~3") maps of CH_3OH, HNCO, HCN, and HCO^+ in the southern portion of the outflow containing B1 and B2, as observed with Combined Array for Research in Millimeter-Wave Astronomy. The HNCO maps are the first interferometric observations of this species in L1157. The maps show distinct differences in the chemistry within the various shocked regions in L1157B. This is further supported through constraints of the molecular abundances using the non-LTE code radex. We find that the east/west chemical differentiation in C2 may be explained by the contrast of the shock's interaction with either cold, pristine material or warm, previously shocked gas, as seen in enhanced HCN abundances. In addition, the enhancement of the HNCO abundance toward the the older shock, B2, suggests the importance of high-temperature O-chemistry in shocked regions

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Methanimine At High Spatial Resolution In Sgr B2: Implications For The Formation Of Cyanomethanimine

Two transitions of methanimine (CH2NH) have been mapped towards Sgr B2 using the Jansky Very Large Array (VLA) with 1.5 arcsecond resolution. The two targeted transitions are both between low-lying energy states at similar frequencies, yet one appears in absorption whereas the other is in emission with the same line profile. The VLA data reveals that the spatial distributions of the two transitions match and that they are NOT associated with the hot core toward Sgr B2(N). As compared to other molecular lines observed towards Sgr B2 at centimeter wavelengths, the CH2NH emission line is highly uncharacteristic, and the transitions exhibits non-thermal effects implying a population inversion. We discuss the non-thermal excitation of CH2NH, observed spatial distributions, and implications for the chemistry in Sgr B2. Specifically, CH2NH may be important for the formation of the recently detected species E-cyanomethanimine [1] and of the Z- and N- conformers of cyanomethanimine. Laboratory work by Balucani et al [2] indicates that reactions between the CN radical and olefins (with a carbon-carbon double bond) may proceed without a barrier, potentially making the reaction CH2NH + CN $\rightarrow$ HCNHCN viable in the interstellar medium. 1 Zaleski, D.P., et al. 2013, ApJL, 765, L10 2 Balucani, N., et al. 2000, ApJ, 545, 89

The Gbt Primos Program: 7 Years Of Astronomical Discovery

The GBT PRebiotic Interstellar MOlecule Survey (PRIMOS) towards Sgr B2N is the deepest, most complete spectral line survey in the range of 300MHz - 49 GHz. PRIMOS enables astronomers, chemists, and biologists to test theories of molecular formation, the origins of organic chemistry and the molecular complexity and physical and kinematic structure of material in our Galaxy. To date, PRIMOS data have resulted in 14 refereed publications since 2007, demonstrating the power of centimeter wave spectroscopy for detecting new organic species and revealing the significance of non-LTE effects including maser amplification in the cm-wave spectra of organic molecules. The survey has additionally advertised molecular astrophysics in public lectures, summer undergraduate diversity programs, and high school student projects. While the GBT is the only telescope in the world capable of conducting the PRIMOS Survey, PRIMOS data couples with newly available broad-bandwidth telescopes including the Jansky Very Large Array and ALMA. Synergistic observations with ALMA will be necessary to fully characterize the spectra of molecular material and determine excitation mechanisms leading to observed line radiation. This presentation provides an overview of the PRIMOS program, highlights PRIMOS science, and describes how the entire astronomical community can obtain the data for their own research

SgrB2

Sagittarius B2 (Sgr B2) is an exceptionally massive (3 × 10^6 M⊙; de Vicente et al. 1996) giant molecular cloud located ~130 pc (Reid et al. 2009) from Sgr A* – the Milky Way Galaxy’s central supermassive black hole – which is at a distance of ~8.5 kpc from Earth (Genzel et al. 2010). Sgr B2 is within the Central Molecular Zone (CMZ) of the Galaxy, a ~300 pc radius region around Sgr A* that exhibits widespread emission from complex organic molecules (COMs), with Sgr B2 containing the most complex identified to date. The Sgr B2 cloud is highly heterogeneous and composed of both compact (hot) and extended (cold) molecular material, molecular maser regions, and ultracompact continuum sources (Remijan et al. 2014)

INTERSTELLAR NITRILE CHEMISTRY AS REVEALED BY CHIRPED-PULSE FTMW SPECTROSCOPY

Author Institution: Department of Chemistry, University of Virginia, McCormick Rd., P.O. Box 400319, Charlottesville, VA 22904.; Department of Astronomy, University of Virginia, McCormick Rd., P.O. Box 400325, Charlottesville, VA 22904.; Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, and School of Engineering and Applied Sciences, Harvard University, 29 Oxford St., Cambridge MA 02138.; National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22904-2475.Nitriles make up a significant fraction of the known interstellar species, in part because their large dipole moments allow for easier detection. The presence of several nitriles in rich interstellar sources makes them a class of molecules that can be used to test proposal for molecule formation in the interstellar medium. We have performed a screening of the laboratory nitrile chemistry produced in a pulsed discharge source using the high abundance interstellar species CH$_3$CN and H$_2$S. The reaction products are identified by broadband rotational spectroscopy in a chirped-pulse FTMW spectrometer. We compare laboratory yields with column densities in Sagittarius B2(N) for several nitriles. We also describe the common lineshapes. So far 25 discharge-induced species, of which 18 are known interstellar molecules, have been identified in the laboratory spectrum. Because the column densities found in the GBT PRIMOS survey of Sgr B2(N) are similar to what is seen in laboratory relative population analysis, it seems to suggest the conditions created by the discharge nozzle may be similar to those found in the interstellar medium. Radicals of CH$_3$CN and H$_2$S are produced in high abundances and can explain many of the observed product species. These comparisons suggest that radical chemistry may dominate nitrile formation in some interstellar sources