90GHz and 150GHz observations of the Orion M42 region. A sub-millimeter to radio analysis

We have used the new 90GHz MUSTANG camera on the Robert C. Byrd Green Bank Telescope (GBT) to map the bright Huygens region of the star-forming region M42 with a resolution of 9" and a sensitivity of 2.8mJy/beam. 90GHz is an interesting transition frequency, as MUSTANG detects both the free-free emission characteristic of the HII region created by the Trapezium stars, normally seen at lower frequencies, and thermal dust emission from the background OMC1 molecular cloud, normally mapped at higher frequencies. We also present similar data from the 150GHz GISMO camera taken on the IRAM telescope. This map has 15" resolution. By combining the MUSTANG data with 1.4, 8, and 21GHz radio data from the VLA and GBT, we derive a new estimate of the emission measure (EM) averaged electron temperature of Te = 11376K by an original method relating free-free emission intensities at optically thin and optically thick frequencies. Combining ISO-LWS data with our data, we derive a new estimate of the dust temperature and spectral emissivity index within the 80" ISO-LWS beam toward OrionKL/BN, Td = 42K and Beta=1.3. We show that both Td and Beta decrease when going from the HII region and excited OMC1 interface to the denser UV shielded part of OMC1 (OrionKL/BN, Orion S). With a model consisting of only free-free and thermal dust emission we are able to fit data taken at frequencies from 1.5GHz to 854GHz.Comment: 18 pages, 8 figures, submitted to the Astrophysical Journa

Multi-level selectional stalemate in a simple artificial chemistry

We describe a simple artificial chemistry which abstracts a small number of key features from the origin of life "replicator world" hypotheses. We report how this can already give rise to moderately complex and counter-intuitive evolutionary phenomena, including macro- evolutionary deterioration in replication fidelity (which corresponds to intrinsic replicator fitness in this model). We briefly describe the extension of this model to incorporate a higher, protocell, level of selection. We show that the interaction between the two levels of selection then serves to control parasitic exploitation at the molecular level, while still significantly constraining accessible evolutionary trajectories at the protocell level. We conclude with a brief discussion of the implications for further work

Atomic Carbon in M82: Physical conditions derived from simultaneous observations of the [CI] fine structure submillimeter wave transitions

We report the first extragalactic detection of the neutral carbon [CI] 3P2-3P1 fine structure line at 809 GHz. The line was observed towards M82 simultaneously with the 3P1-3P0 line at 492 GHz, providing a precise measurement of the J=2-1/J=1-0 integrated line ratio of 0.96 (on a [K km s^-1] -scale). This ratio constrains the [CI] emitting gas to have a temperature of at least 50 K and a density of at least 10^4 cm^-3. Already at this minimum temperature and density, the beam averaged CI-column density is large, 2.1 10^18 cm^-2, confirming the high CI/CO abundance ratio of approximately 0.5 estimated earlier from the 492 GHz line alone. We argue that the [CI] emission from M82 most likely arises in clouds of linear size around a few pc with a density of about 10^4 cm^-3 or slightly higher and temperatures of 50 K up to about 100 K.Comment: 4 pages, 2 figures, ApJL in press, postscript also available at ftp://apollo.ph1.uni-koeln.de/pub/stutzki/m82_pap.ps.gz e-mail-contact:[email protected]

Absence of CALR Mutations in Idiopathic Erythrocytosis Patients with Low Serum Erythropoietin Levels

International audienc

Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range of 1–2 GHz

We report L-band VLA observations of 1RXS J0603.3+4214, a cluster that hosts a bright radio relic, known as the Toothbrush, and an elongated giant radio halo. These new observations allow us to study the surface brightness distribution down to one arcsec resolution with very high sensitivity. Our images provide an unprecedented detailed view of the Toothbrush, revealing enigmatic filamentary structures. To study the spectral index distribution, we complement our analysis with published LOFAR and GMRT observations. The bright `brush' of the Toothbrush shows a prominent narrow ridge to its north with a sharp outer edge. The spectral index at the ridge is in the range $-0.70\leq\alpha\leq-0.80$. We suggest that the ridge is caused by projection along the line of sight. With a simple toy model for the smallest region of the ridge, we conclude that the magnetic field is below $5\,\rm\mu G$ and varies significantly across the shock front. Our model indicates that the actual Mach number is higher than that obtained from the injection index and agrees well with the one derived from the overall spectrum, namely ${\cal M}=3.78^{+0.3}_{-0.2}$. The radio halo shows an average spectral index of $\alpha=-1.16\pm0.05$ and a slight gradient from north to south. The southernmost part of the halo is steeper and possibly related to a shock front. Excluding the southernmost part, the halo morphology agrees very well with the X-ray morphology. A power-law correlation is found between the radio and X-ray surface brightnessComment: 23 pages, 21 figures, accepted for publication in Ap

Young Stars and Protostellar Cores near NGC 2023

We investigate the young (proto)stellar population in NGC 2023 and the L 1630 molecular cloud bordering the HII region IC 434, using Spitzer IRAC and MIPS archive data, JCMT SCUBA imaging and spectroscopy as well as targeted BIMA observations of one of the Class 0 protostars, NGC 2023 MM1. We have performed photometry of all IRAC and MIPS images, and used color-color diagrams to identify and classify all young stars seen within a 22'x26' field along the boundary between IC 434 and L 1630. For some stars, which have sufficient optical, IR, and/or sub-millimeter data we have also used the online SED fitting tool for a large 2D archive of axisymmetric radiative transfer models to perform more detailed modeling of the observed SEDs. We identify 5 sub-millimeter cores in our 850 and 450 micron SCUBA images, two of which have embedded class 0 or I protostars. Observations with BIMA are used to refine the position and characteristics of the Class 0 source NGC 2023 MM 1. These observations show that it is embedded in a very cold cloud core, which is strongly enhanced in NH2D. We find that HD 37903 is the most massive member of a cluster with 20 -- 30 PMS stars. We also find smaller groups of PMS stars formed from the Horsehead nebula and another elephant trunk structure to the north of the Horsehead. We refine the spectral classification of HD 37903 to B2 Ve. Our study shows that the expansion of the IC 434 HII region has triggered star formation in some of the dense elephant trunk structures and compressed gas inside the L 1630 molecular cloud. This pre-shock region is seen as a sub-millimeter ridge in which stars have already formed. The cluster associated with NGC 2023 is very young, and has a large fraction of Class I sources.Comment: 21 pages, 11 figures. Accepted for publication in A&A Replaced with higher resolution figure

Remnant radio-loud AGN in the Herschel-ATLAS field

Only a small fraction of observed active galactic nuclei (AGN) display large-scale radio emission associated with jets, yet these radio-loud AGN have become increasingly important in models of galaxy evolution. In determining the dynamics and energetics of the radio sources over cosmic time, a key question concerns what happens when their jets switch off. The resulting ‘remnant' radio-loud AGN have been surprisingly evasive in past radio surveys, and therefore statistical information on the population of radio-loud AGN in their dying phase is limited. In this paper, with the recent developments of Low-Frequency Array (LOFAR) and the Very Large Array, we are able to provide a systematically selected sample of remnant radio-loud AGN in the Herschel-ATLAS field. Using a simple core-detection method, we constrain the upper limit on the fraction of remnants in our radio-loud AGN sample to 9 per cent, implying that the extended lobe emission fades rapidly once the core/jets turn off. We also find that our remnant sample has a wide range of spectral indices (−1.5 ⩽ α1400150 ⩽ −0.5), confirming that the lobes of some remnants may possess flat spectra at low frequencies just as active sources do. We suggest that, even with the unprecedented sensitivity of LOFAR, our sample may still only contain the youngest of the remnant population