Context. The disc around the Herbig Ae/Be star HD 100546 is one of the most extensively studied discs in the southern sky. Although there is a wealth of information about its dust content and composition, not much is known about its gas and large-scale kinematics. Many recent results have stressed the importance of studying both the gas and dust in discs. 12 CO is an excellent gas tracer in the submillimetre, and the intensity ratio between lines originating from low and high rotational levels probes the gas temperature. Emerging submillimetre facilities in the Southern hemisphere allow us to characterise the gas and dust content in objects like HD 100546 better. Aims. Our aim is to establish whether the disc is gas-rich and to study the disc temperature and kinematics. Methods. We detected and studied the molecular gas in the disc at spatial resolution from 7. 7 to 18. 9 using the Atacama Pathfinder Experiment telescope . We observed the lines 12 CO J = 7−6, J = 6−5, J = 3−2, 13 CO J = 3−2 and [C I] 3 P 2 − 3 P 1 , as diagnostics of disc temperature, size, chemistry, and kinematics. We use parametric disc models that reproduce the low-J 12 CO emission from Herbig Ae stars and we vary the basic disc parameters -temperature, mass, and size. With the help of a molecular excitation and radiative transfer code we fit the observed spectral line profiles. Results. Our observations are consistent with more than 10 −3 M of molecular gas in a disc of ≈400 AU radius in Keplerian rotation around a 2.5 M star, seen at an inclination of 50 • . The detected 12 CO lines are dominated by gas at 30−70 K. Not detecting the [C I] line indicates excess ultraviolet emission above that of a B9 type model stellar atmosphere. Asymmetry in the 12 CO line emission suggests that one side of the outer disc is colder by 10−20 K than the other. A plausible scenario is a warped geometry in the inner disc casting a partial shaddow on the outer disc. We exclude pointing offsets, foreground cloud absorption, and asymmetry in the disc extent as possible causes of the observed line asymmetry. Conclusions. Efficient heating of the outer disc by the star HD 100546 ensures that low-and high-J 12 CO lines are dominated by the outermost disc regions, indicating a 400 AU radius. The 12 CO J = 6−5 line arises from a disc layer higher than disc midplane, and warmer by 15−20 K than the layer emitting the J = 3−2 line. The existing models of discs around Herbig Ae stars, asuming a B9.5 type model stellar atmosphere, overproduce the [CI] 3 P 2 − 3 P 1 line intensity from HD 100546 by an order of magnitude.

Aims. Future astrophysics and cosmic microwave background space missions operating in the far-infrared to millimetre part of the spectrum will require very large arrays of ultra-sensitive detectors in combination with high multiplexing factors and efficient lownoise and low-power readout systems. We have developed a demonstrator system suitable for such applications. Methods. The system combines a 961 pixel imaging array based upon Microwave Kinetic Inductance Detectors (MKIDs) with a readout system capable of reading out all pixels simultaneously with only one readout cable pair and a single cryogenic amplifier. We evaluate, in a representative environment, the system performance in terms of sensitivity, dynamic range, optical efficiency, cosmic ray rejection, pixel-pixel crosstalk and overall yield at an observation centre frequency of 850 GHz and 20% fractional bandwidth. Results. The overall system has an excellent sensitivity, with an average detector sensitivity NEP det = 3 × 10 −19 W/ √ Hz measured using a thermal calibration source. At a loading power per pixel of 50 fW we demonstrate white, photon noise limited detector noise down to 300 mHz. The dynamic range would allow the detection of ∼1 Jy bright sources within the field of view without tuning the readout of the detectors. The expected dead time due to cosmic ray interactions, when operated in an L2 or a similar far-Earth orbit, is found to be <4%. Additionally, the achieved pixel yield is 83% and the crosstalk between the pixels is <−30 dB. Conclusions. This demonstrates that MKID technology can provide multiplexing ratios on the order of a 1000 with state-of-the-art single pixel performance, and that the technology is now mature enough to be considered for future space based observatories and experiments.

Context. The gas-solid budget of carbon in protoplanetary disks is related to the composition of the cores and atmospheres of the planets forming in them. The principal gas-phase carbon carriers CO, C 0 , and C + can now be observed regularly in disks. Aims. The gas-phase carbon abundance in disks has thus far not been well characterized observationally. We obtain new constraints on the [C]/[H] ratio in a large sample of disks, and compile an overview of the strength of [C ] and warm CO emission. Methods. We carried out a survey of the CO 6-5 line and the [C ] 1-0 and 2-1 lines towards 37 disks with the APEX telescope, and supplemented it with [C ] data from the literature. The data are interpreted using a grid of models produced with the DALI disk code.We also investigate how well the gas-phase carbon abundance can be determined in light of parameter uncertainties.

The Néel IRAM KIDs Array (NIKA) is a fully integrated measurement system based on kinetic inductance detectors (KIDs) currently being developed for millimeter wave astronomy. The instrument includes dual-band optics allowing simultaneous imaging at 150 GHz and 220 GHz. The imaging sensors consist of two spatially separated arrays of KIDs. The first array, mounted on the 150 GHz branch, is composed of 144 lumped-element KIDs. The second array (220 GHz) consists of 256 antenna-coupled KIDs. Each of the arrays is sensitive to a single polarization; the band splitting is achieved by using a grid polarizer. The optics and sensors are mounted in a custom dilution cryostat, with an operating temperature of ∼70 mK. Electronic readout is realized using frequency multiplexing and a transmission line geometry consisting of a coaxial cable connected in series with the sensor array and a lownoise 4 K amplifier. The dual-band NIKA was successfully tested in 2010 October at the Institute for Millimetric Radio Astronomy (IRAM) 30 m telescope at Pico Veleta, Spain, performing in-line with laboratory predictions. An optical NEP was then calculated to be around 2 × 10 −16 W Hz −1/2 (at 1 Hz) while under a background loading of approximately 4 pW pixel −1 . This improvement in comparison with a preliminary run (2009) verifies that NIKA is approaching the target sensitivity for photon-noise limited ground-based detectors. Taking advantage of the larger arrays and increased sensitivity, a number of scientifically relevant faint and extended objects were then imaged including the Galactic Center SgrB2 (FIR1), the radio galaxy Cygnus A, and the NGC1068 Seyfert galaxy. These targets were all observed simultaneously in the 150 GHz and 220 GHz atmospheric windows.