The A&A Experience With Impact Factors

There is a widespread impression that the scientific journal "Astronomy & Astrophysics" (A&A) has a smaller impact, as measured by citations to articles, than some of the other major astronomy journals. This impression was apparently supported - and probably created - by the Journal Citation Report (JCR), which is prepared annually by the Institute of Scientific Information (ISI) Web of Knowledge. The published poor impact factor of A&A was in fact wrong and was due to a serious flaw in the method used by ISI Web of Knowledge to determine it. The resulting damage inflicted upon A&A by the JCR is incalculable.Comment: 4 pages, to be published in A. Heck (ed.) "Organizations and Strategies in Astronomy, Vol. 5" (Kluwer, 2004

Odin observations of ammonia in the Sgr A +50 km/s Cloud and Circumnuclear Disk

Context. The Odin satellite is now into its sixteenth year of operation, much surpassing its design life of two years. One of the sources which Odin has observed in great detail is the Sgr A Complex in the centre of the Milky Way. Aims. To study the presence of NH3 in the Galactic Centre and spiral arms. Methods. Recently, Odin has made complementary observations of the 572 GHz NH3 line towards the Sgr A +50 km/s Cloud and Circumnuclear Disk (CND). Results. Significant NH3 emission has been observed in both the +50 km/s Cloud and the CND. Clear NH3 absorption has also been detected in many of the spiral arm features along the line of sight from the Sun to the core of our Galaxy. Conclusions. The very large velocity width (80 km/s) of the NH3 emission associated with the shock region in the southwestern part of the CND may suggest a formation/desorption scenario similar to that of gas-phase H2O in shocks/outflows.Comment: 5 pages, 3 figures, 3 table

Herschel and Odin observations of H2O, CO, CH, CH+, and NII in the barred spiral galaxy NGC 1365. Bar-induced activity in the outer and inner circumnuclear tori

The Odin satellite is now into its twentieth year of operation, much surpassing its design life of two years. One of its major pursuits was the search for and study of H2O in the Solar System and the Milky Way galaxy. Herschel has observed the central region of NGC 1365 in two positions, and both its SPIRE and PACS observations are available in the Herschel Science Archive. Herschel PACS images have been produced of the 70 and 160 micron infrared emission from the whole galaxy, and also of the cold dust distribution as obtained from the ratio of the 160 to 70 micron images. The Herschel SPIRE observations have been used to produce maps of the 557 GHz o-H2O, 752 GHz p-H2O, 691 GHz CO(6-5), 1037 GHz CO(9-8), 537 GHz CH, 835 GHz CH+, and the 1461 GHz NII lines; however, these observations have no effective velocity resolution. Odin has recently observed the 557 GHz o-H2O ground state line in the central region with high (5 km/s) spectral resolution. The emission and absorption of H2O at 557 GHz, with a velocity resolution of 5 km/s, has been marginally detected in NGC 1365 with Odin. The H2O is predominantly located in a shocked 15" (1.3 kpc) region near some central compact radio sources and hot-spot HII regions, close to the northeast component of the molecular torus surrounding the nucleus. An analysis of the H2O line intensities and velocities indicates that a shock-region is located here. This is corroborated by a statistical image deconvolution of our SEST CO(3-2) observations, yielding 5" resolution, and a study of our VLA HI absorption observations. Additionally, an enticing 20" HI ridge is found to extend south-southeast from the nucleus, coinciding in position with the southern edge of an OIII outflow cone, emanating from the nucleus. The molecular chemistry of the shocked central region is analyzed with special emphasis on the CO, H2O and CH, CH+ results.Comment: 25 pages, 11 figure

Odin observations of the Galactic centre in the 118-GHz band. Upper limit to the O2 abundance

The Odin satellite has been used to search for the 118.75-GHz line of molecular oxygen (O2)in the Galactic centre. Odin observations were performed towards the Sgr A* circumnuclear disk (CND), and the Sgr A +20 km/s and +50 km/s molecular clouds using the position-switching mode. Supplementary ground-based observations were carried out in the 2-mm band using the ARO Kitt Peak 12-m telescope to examine suspected SiC features. A strong emission line was found at 118.27 GHz, attributable to the J=13-12 HC3N line. Upper limits are presented for the 118.75-GHz O2 (1,1-1,0) ground transition line and for the 118.11-GHz 3Pi2, J=3-2 ground state SiC line at the Galactic centre. Upper limits are also presented for the 487-GHz O2 line in the Sgr A +50 km/s cloud and for the 157-GHz, J=4-3, SiC line in the Sgr A +20 and +50 km/s clouds, as well as the CND. The CH3OH line complex at 157.2 - 157.3 GHz has been detected in the +20 and +50 km/s clouds but not towards Sgr A*/CND. A 3-sigma upper limit for the fractional abundance ratio of [O2]/[H2] is found to be X(O2) < 1.2 x 10exp(-7) towards the Sgr A molecular belt region.Comment: Accepted for publication in A&A. 6 journal pages, 5 figure

Ground-state ammonia and water in absorption towards Sgr B2

We have used the Odin submillimetre-wave satellite telescope to observe the ground state transitions of ortho-ammonia and ortho-water, including their 15N, 18O, and 17O isotopologues, towards Sgr B2. The extensive simultaneous velocity coverage of the observations, >500 km/s, ensures that we can probe the conditions of both the warm, dense gas of the molecular cloud Sgr B2 near the Galactic centre, and the more diffuse gas in the Galactic disk clouds along the line-of-sight. We present ground-state NH3 absorption in seven distinct velocity features along the line-of-sight towards Sgr B2. We find a nearly linear correlation between the column densities of NH3 and CS, and a square-root relation to N2H+. The ammonia abundance in these diffuse Galactic disk clouds is estimated to be about (0.5-1)e-8, similar to that observed for diffuse clouds in the outer Galaxy. On the basis of the detection of H218O absorption in the 3 kpc arm, and the absence of such a feature in the H217O spectrum, we conclude that the water abundance is around 1e-7, compared to ~1e-8 for NH3. The Sgr B2 molecular cloud itself is seen in absorption in NH3, 15NH3, H2O, H218O, and H217O, with emission superimposed on the absorption in the main isotopologues. The non-LTE excitation of NH3 in the environment of Sgr B2 can be explained without invoking an unusually hot (500 K) molecular layer. A hot layer is similarly not required to explain the line profiles of the 1_{1,0}-1_{0,1} transition from H2O and its isotopologues. The relatively weak 15NH3 absorption in the Sgr B2 molecular cloud indicates a high [14N/15N] isotopic ratio >600. The abundance ratio of H218O and H217O is found to be relatively low, 2.5--3. These results together indicate that the dominant nucleosynthesis process in the Galactic centre is CNO hydrogen burning.Comment: 10 pages, 5 figure

Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)

The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January - 3 February 2015. We detected 22 molecules and several isotopologues. The H$_2^{16}$O and H$_2^{18}$O production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of ~25%. The inferred isotope ratios in comet Lovejoy are $^{16}$O/$^{18}$O = 499 $\pm$ 24 and D/H = 1.4 $\pm$ 0.4 $\times 10^{-4}$ in water, $^{32}$S/$^{34}$S = 24.7 $\pm$ 3.5 in CS, all compatible with terrestrial values. The ratio $^{12}$C/$^{13}$C = 109 $\pm$ 14 in HCN is marginally higher than terrestrial and $^{14}$N/$^{15}$N = 145 $\pm$ 12 in HCN is half the Earth ratio. Several upper limits for D/H or 12C/13C in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.Comment: Accepted for publication in Astronomy and Astrophysic

Herschel HIFI Observations of the Sgr A +50 km s^(-1) Cloud. Deep Searches for O_2 in Emission and Foreground Absorption

Context. The Herschel Oxygen Project (HOP) is an open time key program, awarded 140 h of observing time to search for molecular oxygen (O_2) in a number of interstellar sources. To date O_2 has definitely been detected in only two sources, namely ρ Oph A and Orion, reflecting the extremely low abundance of O_2 in the interstellar medium. Aims. One of the sources in the HOP program is the +50 km s^(-1) Cloud in the Sgr A Complex in the centre of the Milky Way. Its environment is unique in the Galaxy and this property is investigated to see if it is conducive to the presence of O_2. Methods. The Herschel Heterodyne Instrument for the Far Infrared (HIFI) is used to search for the 487 and 774 GHz emission lines of O_2. Results. No O_2 emission is detected towards the Sgr A +50 km s^(-1) Cloud, but a number of strong emission lines of methanol (CH_3OH) and absorption lines of chloronium (H_2Cl^+) are observed. Conclusions. A 3σ upper limit for the fractional abundance ratio of [O_2]/[H_2] in the Sgr A +50 km s^(-1) Cloud is found to be X(O_2) ≤ 5 × 10^(-8). However, since we can find no other realistic molecular candidate than O_2 itself, we very tentatively suggest that two weak absorption lines at 487.261 and 487.302 GHz may be caused by the 487 GHz line of O_2 in two foreground spiral arm clouds. By considering that the absorption may only be apparent, the estimated upper limit to the O_2 abundance of ≤ (10^(−20)) × 10^(-6) in these foreground clouds is very high, as opposed to the upper limit in the Sgr A +50 km s^(-1) Cloud itself, but similar to what has been reached in recent chemical shock models for Orion. This abundance limit was determined also using Odin non-detection limits, and assumes that O_2 fills the beam. If the absorption is due to a differential Herschel OFF-ON emission, the O_2 fractional abundance may be of the order of ≈ (5−10) × 10^(-6). With the assumption of pure absorption by foreground clouds, the unreasonably high abundance of (1.4−2.8) × 10^(-4) was obtained. The rotation temperatures for CH_3OH-A and CH_3OH-E lines in the +50 km s^(-1) Cloud are found to be ≈ 64 and 79 K, respectively, and the fractional abundance of CH_3OH is approximately 5 × 10^(-7)

Searching for O2_2 in the SMC:Constraints on Oxygen Chemistry at Low Metallicities

We present a 39 h integration with the Odin satellite on the ground-state 118.75 GHz line of O2 towards the region of strongest molecular emission in the Small Magellanic Cloud. Our 3sigma upper limit to the O2 integrated intensity of <0.049 K km/s in a 9'(160 pc) diameter beam corresponds to an upper limit on the O2/H2 abundance ratio of <1.3E-6. Although a factor of 20 above the best limit on the O2 abundance obtained for a Galactic source, our result has interesting implications for understanding oxygen chemistry at sub-solar metal abundances. We compare our abundance limit to a variety of astrochemical models and find that, at low metallicities, the low O2 abundance is most likely produced by the effects of photo-dissociation on molecular cloud structure. Freeze-out of molecules onto dust grains may also be consistent with the observed abundance limit, although such models have not yet been run at sub-solar initial metallicities.Comment: 4 pages, accepted to A&A Letter