Papers by Christian Henkel
Context. In our previous work we found a statistically significant offset ∆V ≈ 27 m s −1 between ... more Context. In our previous work we found a statistically significant offset ∆V ≈ 27 m s −1 between the radial velocities of the HC3N J = 2 − 1 and NH3 (J, K) = (1, 1) transitions observed in molecular cores from the Milky Way. This may indicate that the electron-to-proton mass ratio, µ ≡ me/mp, increases by ∼ 3 × 10 −8 when measured under interstellar conditions with matter densities of more than 10 orders of magnitude lower as compared with laboratory (terrestrial) environments. Aims. We map four molecular cores L1498, L1512, L1517, and L1400K selected from our previous sample in order to estimate systematic effects in ∆V due to possible velocity gradients or other sources across the cloud, and to check the reproducibility of the velocity offsets on the year-to-year time base. Methods. We use the ammonia method, which involves observations of inversion lines of NH3 complemented by rotational lines of other molecular species and allows us to test changes in µ due to a higher sensitivity of the inversion frequencies to the µ-variation as compared with the rotational frequencies.
A multi-line millimeter-wave study of the nearby southern starburst galaxy NGC4945 has been carri... more A multi-line millimeter-wave study of the nearby southern starburst galaxy NGC4945 has been carried out using the Swedish-ESO Submillimetre Telescope (SEST). The study covers the frequency range from 81 GHz to 355 GHz and 71 transitions of 17 molecules including their rare isotope-bearing species have been measured. For instance HC3N has been observed in 9 rotational transitions; five of them are detected positively and two tentatively. Similar work has been done for H2CO SO C3H2 and other species. Combining all this information abundances and therefore the chemistry of many molecules are calculated and compared with results obtained from the starburst galaxies NGC253 and M82. Details will be given during the Joint Discussion 21.
We report new detections of three H2O megamasers and one kilomaser using the Effelsberg 100-m tel... more We report new detections of three H2O megamasers and one kilomaser using the Effelsberg 100-m telescope. Isotropic luminosities are ~50 300 1 and 230 solar luminosities for Mrk 1066 Mrk 34 NGC 3556 and Arp 299 respectively. Mrk 34 contains the most distant H2O megamaser ever detected. Our targets in this survey were chosen to fit one of the following criteria: 1) to have a high probability of interaction between the radio jet and the ISM within the central few parsecs of the radio galaxy yielding masers which arise in local molecular clouds (e.g. Mrk 348); or 2) were very bright IRAS sources in which massive star-forming regions might yield extremely bright masers (e.g. NGC 2146). The ""jet maser"" sources can provide detailed information about the conditions in the ISM in the central 1-10 pc of AGN. The ""star-formation masers"" can be used to pinpoint and characterize locations of high mass star formation in nearby galaxies. Both of these newly discovered types of masers will lead to a better understanding of the local chemistry in the molecular clouds in external galaxies.
Proceedings of the International Astronomical Union
ABSTRACT
Detections of extragalactic HC15N are reported from the Large Magellanic Cloud (LMC) and the core... more Detections of extragalactic HC15N are reported from the Large Magellanic Cloud (LMC) and the core of the (post-) starburst galaxy NGC 4945. The LMC data from the massive star-forming region N113 directly infer 14N / 15N = 114 +/- 14. For the LMC star-forming region N159 and for the central region of NGC 4945, the use of a `reasonable' carbon
We present results of an HST survey in Halpha and continuum filters of a sample of H2O megamaser ... more We present results of an HST survey in Halpha and continuum filters of a sample of H2O megamaser galaxies compiled by Braatz et al., all of which contain AGN. These observations allow us to study the AGN/host-galaxy connection, e.g. study the relation between the parsec scale masing disk/torus, bipolar outflows, and large scale properties of the galaxies such as dust lanes, signs for interaction, and galaxy types. A number of galaxies indeed show large-scale bi-polar Halpha structures which, however, are more reminiscent of outflows than excitation cones. Most megamaser galaxies are found in spiral galaxies. Only one galaxy in the original sample is known to be an elliptical and one galaxy imaged by us shows clear signs of interactions. In all cases we see evidence for obscuration of the nucleus (e.g. dust-lanes) in our color maps and the disk galaxies are preferentially edge on. This suggests that the nuclear masing disk has some relation to the large scale properties of the galaxy and the dust distribution.
Proceedings of the International Astronomical Union
ABSTRACT
Astronomische Nachrichten
Centaurus A is by far the nearest active radio galaxy. Water maser emission is capable to provide... more Centaurus A is by far the nearest active radio galaxy. Water maser emission is capable to provide fundamental information of the inner region of highly obscured nuclear regions of galaxy. Unfortunately, due to the sstrong radio continuum from the galaxy the single-dish spectrum are corrupted by standing waves. Hence, we propose to use the ATCA interferometer to perform a search for maser emission in CenA. A detection would yield unprecedented new possibilities to study the central environments of radio galaxies.
In continuation of the ATCA Galactic Centre Ammonia Survey, which was started last winter at the ... more In continuation of the ATCA Galactic Centre Ammonia Survey, which was started last winter at the ATCA, we apply for additional 12mm observations with the Mopra telescope. The observations are critical to fill in the missing short spacings of the ATCA NH3 (1,1) and (2,2) data. In addition, with the new MOPS correlator, we will observe all lines in the 19-27GHz band, which contains all metastable ammonia lines from (1,1) up to (7,7) and many non-metastable ammonia lines. This combination will be a unique data base for extensive radiative transfer models. In addition, the survey will encompass other molecular species such as water, OH, and methanol lines. This combination of lines will provide the most comprehensive 12mm spectral line survey of the Galactic Center to date.
Uploads
Papers by Christian Henkel