Detection of the linear radical HC4N in IRC+10216

We report the detection of the linear radical HC4N in the C-rich envelope of IRC+10216. After HCCN, HC4N is the second member of the allenic chain family HC_(2n)N observed in space. The column density of HC4N is found to be 1.5 10**12 cm**(-2). The abundance ratio HC2N/HC4N is 9, a factor of two larger than the decrement observed for the cyanopolyynes HC$_(2n+1)N/HC_(2n+3)N. Linear HC_4N has a 3-Sigma electronic ground state and is one of the 3 low-energy isomeric forms of this molecule. We have searched for the bent and ringed HC4N isomers, but could only derive an upper limit to their column densities of about 3 10**(12) cm**(-2).Comment: Preprint of 10 page

Isotopic ratios at z=0.68 from molecular absorption lines toward B 0218+357

Isotopic ratios of heavy elements are a key signature of the nucleosynthesis processes in stellar interiors. The contribution of successive generations of stars to the metal enrichment of the Universe is imprinted on the evolution of isotopic ratios over time. We investigate the isotopic ratios of carbon, nitrogen, oxygen, and sulfur through millimeter molecular absorption lines arising in the z=0.68 absorber toward the blazar B 0218+357. We find that these ratios differ from those observed in the Galactic interstellar medium, but are remarkably close to those in the only other source at intermediate redshift for which isotopic ratios have been measured to date, the z=0.89 absorber in front of PKS1830-211. The isotopic ratios in these two absorbers should reflect enrichment mostly from massive stars, and they are indeed close to the values observed toward local starburst galaxies. Our measurements set constraints on nucleosynthesis and chemical evolution models.Comment: Accepted for publication in Astronomy & Astrophysics; 10 pages, 9 figure

Detection of CO in the inner part of M31's bulge

We report the first detection of CO in M31's bulge. The 12CO (1-0) and (2-1) lines are both detected in the dust complex D395A/393/384, at 1.3" (~0.35 kpc) from the centre. From these data and from visual extinction data, we derive a CO-luminosity to reddening ratio (and a CO-luminosity to H_2 column density ratio) quite similar to that observed in the local Galactic clouds. The (2-1) to (1-0) line intensity ratio points to a CO rotational temperature and a gas kinetic temperature > 10 K. The molecular mass of the complex, inside a 25' (100 pc) region, is 1.5 10^4 Mo.Comment: 5 pages including 4 figures (2 in colour

A new infrared band in the Interstellar and Circumstellar Clouds: C_4 or C_4H?

We report on the detection with the Infrared Space Observatory (ISO) of a molecular band at 57.5 microns (174 cm^{-1}) in carbon-rich evolved stars and in Sgr B2. Taking into account the chemistry of these objects the most likelihood carrier is a carbon chain. We tentatively assign the band to the nu_5 bending mode of C_4 for which a wavenumber of 170-172.4 cm^{-1} has been derived in matrix experiments (Withey et al. 1991). An alternate carrier might be C_4H, although the frequency of its lowest energy vibrational bending mode, nu_7, is poorly known (130-226 cm^{-1}). If the carrier is C_4, the derived maximum abundance is nearly similar to that found for C_3 in the interstellar and circumstellar media by Cernicharo, Goicoechea & Caux (2000). Hence, tetra-atomic carbon could be one of the most abundant carbon chain molecules in these media.Comment: 11 pages, 1 figure, accepted in ApJ Letter

Detection of circumstellar CH2CHCN, CH2CN, CH3CCH and H2CS

We report on the detection of vinyl cyanide (CH2CHCN), cyanomethyl radical (CH2CN), methylacetylene (CH3CCH) and thioformaldehyde (H2CS) in the C-rich star IRC +10216. These species, which are all known to exist in dark clouds, are detected for the first time in the circumstellar envelope around an AGB star. The four molecules have been detected trough pure rotational transitions in the course of a 3 mm line survey carried out with the IRAM 30-m telescope. The molecular column densities are derived by constructing rotational temperature diagrams. A detailed chemical model of the circumstellar envelope is used to analyze the formation of these molecular species. We have found column densities in the range 5 x 10^(12)- 2 x 10^(13) cm^(-2), which translates to abundances relative to H2 of several 10^(-9). The chemical model is reasonably successful in explaining the derived abundances through gas phase synthesis in the cold outer envelope. We also find that some of these molecules, CH2CHCN and CH2CN, are most probably excited trough infrared pumping to excited vibrational states. The detection of these species stresses the similarity between the molecular content of cold dark clouds and C-rich circumstellar envelopes. However, some differences in the chemistry are indicated by the fact that in IRC +10216 partially saturated carbon chains are present at a lower level than those which are highly unsaturated, while in TMC-1 both types of species have comparable abundances.Comment: 9 pages, 5 figures; accepted for publication in A&

13CO at the centre of M82

Using the IRAM interferometer, we have observed the nearby starburst galaxy M82 with a 4.2" resolution (~70 pc) in the 1->0 line of 13CO and in the 2.6-mm continuum. The spatial distribution of the 13CO line shows the same gross features as the 12CO(1->0) map of Shen & Lo (1995), namely two lobes and a compact central source, though with different relative intensities. The lobes are more conspicuous and the central source is fainter in 13CO than in 12CO. The velocity field observed around the nucleus shows a very steep gradient (140 km/s over 75 pc), which is very probably caused by the stellar bar visible in the near infrared. The dynamical centre coincides with the IR peak and is shifted 6" north-east of the compact 13CO source. The two CO lobes appear to be associated with the ends of the bar and not with a molecular ring, as usually assumed. They are probably shaped by the strong UV radiation from the central region. 13CO must be more photodissociated than the self-shielded 12CO molecules in the central ~250 pc region, which may explain the relative weakness of the 13CO central source. A 130 pc-wide bubble of molecular gas has been identified, which happens to host the most luminous compact radio source in M82. It lies 120 pc west of the IR peak between the central source and the western lobe and seems characterized by warmer gas, strong UV radio free-free radiation, and an enhanced cosmic ray production rate.Comment: Accepted by A&A; 9 pages, 9 ps figures, needs LaTeX 2e A&A macro and psfig Styl

Afg3p, a mitochondrial atp-dependent metalloprotease, is involved in degradation of mitochondrially-encoded cox1, cox3, cob, su6, su8 and su9 subunits of the inner membrane complex-III, complex-IV and complex-V

AbstractThe yeast AFG3 gene encodes an ATP-dependent metalloprotease belonging to a subgroup of the AAA-family. This protease has been suggested to be essential for a metal- and ATP-dependent breakdown of incompletely mitochondrially synthesized polypeptides in the inner membrane, a process proposed to be important for mitochondrial function (Pajic et al. (1994) FEBS Lett. 353, 201–206). Here, we confirm the proteolytic activity by site-directed mutagenesis and demonstrate that the proteins Cox1, Cox3, Cob, Su6, Su8 and Su9 are substrates of Afg3p. Surprisingly, this proteolytic activity is not required for respiratory function and thus presumably also not essential for mitochondrial biogenesis

Laboratory And Astronomical Detection Of The Negative Molecular Ion C3N-

The negative molecular ion C3N- has been detected at millimeter wavelengths in a low-pressure laboratory discharge, and then with frequencies derived from the laboratory data in the molecular envelope of IRC+10216. Spectroscopic constants derived from laboratory measurements of 12 transitions between 97 and 378 GHz allow the rotational spectrum to be calculated well into the submillimeter-wave band to 0.03 km s(-1) or better in equivalent radial velocity. Four transitions of C3N- were detected in IRC+10216 with the IRAM 30 m telescope at precisely the frequencies calculated from the laboratory measurements. The column density of C3N- is 0.5% that of C3N, or approximately 20 times greater than that of C4H- relative to C4H. The C3N- abundance in IRC+10216 is compared with a chemical model calculation by Petrie & Herbst. An upper limit in TMC-1 for C3N- relative to C3N (< 0.8%) and a limit for C4H- relative to C4H (< 0.004%) that is 5 times lower than that found in IRC+10216, were obtained from observations with the NRAO 100 m Green Bank Telescope (GBT). The fairly high concentration ofNRFKorean government MEST 2012R1A1A1014646, 2012M4A2026720Southeast Physics Network (SEP-Net)Science and Technology Facilities Council ST/F002858/1, ST/I000976/1Swedish Research Council 2009-4088U.S. NSF AST-0708176, AST-1009799NASA NNX07AH09G, NNG04G177G, NNX11AE09GChandra grant SAO TM8-9009XBiochemistr