Context. Thanks to its excellent 5100 m high site in Chajnantor, the Atacama Pathfinder Experiment (APEX) systematically explores the southern sky at submillimeter wavelengths, in both continuum and spectral line emission. Studying continuum emission from interstellar dust is essential to locating the highest density regions in the interstellar medium, and deriving their masses, column densities, density structures, and large-scale morphologies. In particular, the early stages of (massive) star formation remain poorly understood, mainly because only small samples of high-mass proto-stellar or young stellar objects have been studied in detail so far. Aims. Our goal is to produce a large-scale, systematic database of massive pre-and proto-stellar clumps in the Galaxy, to understand how and under what conditions star formation takes place. Only a systematic survey of the Galactic Plane can provide the statistical basis for unbiased studies. A well characterized sample of Galactic star-forming sites will deliver an evolutionary sequence and a mass function of high-mass, star-forming clumps. This systematic survey at submillimeter wavelengths also represents a preparatory work for Herschel and ALMA. Methods. The APEX telescope is ideally located to observe the inner Milky Way. The Large APEX Bolometer Camera (LABOCA) is a 295-element bolometer array observing at 870 μm, with a beam size of 19. 2. Taking advantage of its large field of view (11. 4) and excellent sensitivity, we started an unbiased survey of the entire Galactic Plane accessible to APEX, with a typical noise level of 50−70 mJy/beam: the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). Results. As a first step, we covered ∼95 deg 2 of the Galactic Plane. These data reveal ∼6000 compact sources brighter than 0.25 Jy, or 63 sources per square degree, as well as extended structures, many of them filamentary. About two thirds of the compact sources have no bright infrared counterpart, and some of them are likely to correspond to the precursors of (high-mass) proto-stars or protoclusters. Other compact sources harbor hot cores, compact H ii regions, or young embedded clusters, thus tracing more evolved stages after massive stars have formed. Assuming a typical distance of 5 kpc, most sources are clumps smaller than 1 pc with masses from a few 10 to a few 100 M . In this first introductory paper, we show preliminary results from these ongoing observations, and discuss the mid-and long-term perspectives of the survey.

Observations of the galaxy cluster MACS J2135-0102 (z cl =0.325) were made with the LABOCA 870µm bolometer camera 29 on the APEX telescope on 2009 May 8 for a total of 3.2hours (1200 seconds on-source) in excellent conditions (PWV=0.35-0.40mm). We used a 6 arcminute spiral pattern scan, centered at α:21:35:12.706 δ:-01:01:43.27 (J2000). For flux calibration, Mars and Uranus were both observed immediately prior to the science observations. The data were reduced using the minicrush reduction package, which includes temperature drift correction, flat-fielding, opacity correction, bad bolometer masking and de-spiking 29 . The final map appears flat, and has an r.m.s. of 3.5mJy/beam. Including systematic effects, we estimate calibration and fitting uncertainties as ~4% and 6% respectively. Visual inspection of the image shows a bright 30σ source centered at α:21:35:11.6 δ:-01:02:52.0 with an 870µm flux of 106.0±3.5mJy. Given the uncertainties in the calibration we adopt the flux of the SMG as S 870 =106.5±7.0mJy, and derive S 870 =24.2±7.0mJy for the counter-image.We followed up SMMJ2135-0102 with the Submillimetre APEX Bolometer CAmera (SABOCA, Siringo et al., in prep.) on the APEX telescope on UT 2009 September 20 and 21. SABOCA is a 37 superconducting Transition Edge Sensing (TES) bolometer array with hexagonal layout and twobeam separation on sky Its filter transmission curve is optimised to cover the 350µm window, and has a central wavelength of 352µm (852 GHz) for flat spectrum sources. SABOCA operates at a temperature of 300mK and is installed in the Cassegrain cabin of APEX. We observed SMMJ2135-0102 in a 20"x20" raster of spirals with 35 seconds duration in order to obtain a fully sampled map.

The Large APEX BOlometer CAmera, LABOCA, has been commissioned for operation as a new facility instrument at the Atacama Pathfinder Experiment 12 m submillimeter telescope. This new 295-bolometer total power camera, operating in the 870 μm atmospheric window, combined with the high efficiency of APEX and the excellent atmospheric transmission at the site, offers unprecedented capability in mapping submillimeter continuum emission for a wide range of astronomical purposes.

We present large scale 870 μm maps of the nearby starburst galaxies NGC 253 and NGC 4945 as well as the nearest giant elliptical radio galaxy Centaurus A (NGC 5128) obtained with the newly commissioned Large Apex Bolometer Camera (LABOCA) operated at the Atacama Pathfinder Experiment telescope. Our continuum images reveal for the first time the distribution of cold dust at a angular resolution of 20 across the entire optical disks of NGC 253 and NGC 4945 out to a radial distance of 10 (7.5 kpc). In NGC 5128 our LABOCA image also shows, for the first time at submillimeter wavelengths, the synchrotron emission associated with the radio jet and the inner radio lobes. From an analysis of the 870 μm emission in conjunction with ISO-LWS, IRAS and long wavelengths radio data we find temperatures for the cold dust in the disks of all three galaxies of 17−20 K, comparable to the dust temperatures in the disk of the Milky Way. The total gas mass in the three galaxies is determined to be 2.1, 4.2 and 2.8 × 10 9 M for NGC 253, NGC 4945 and NGC 5128, respectively. The mass of the warmer (30−40 K) gas associated with the central starburst regions in NGC 253 and NGC 4945 only accounts for ∼10% of the total gas mass. A detailed comparison between the gas masses derived from the dust continuum and the integrated CO(1−0) intensity in NGC 253 suggests that changes of the CO luminosity to molecular mass conversion factor are mainly driven by a metallicity gradient and only to a lesser degree by variations of the CO excitation. An analysis of the synchrotron spectrum in the northern radio lobe of NGC 5128 shows that the synchrotron emission from radio to the ultraviolet (UV) wavelengths is well described by a broken power law and that the break frequency is a function of the distance from the radio core as expected for aging electrons. We derive an outflow speed of ∼0.5 c at a distance of 2.6 kpc from the center, consistent with the speed derived in the vicinity of the nucleus.

The Atacama Large Millimeter-submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that utilizes the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions we derive quiet-Sun values at disk center of 7300 K at λ = 3 mm and 5900 K at λ = 1.3 mm. These values have statistical uncertainties of order 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of order 25 ′′ , the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plage are amongst the hotter features while a large sunspot umbra shows up as a depression and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images.

Aims. With the afterglow of GRB 100621A being the brightest detected so far in X-rays, and superb GROND coverage in the optical/near-infrared during the first few hours, an observational verification of basic fireball predictions seemed possible. Methods. In order to constrain the broad-band spectral energy distribution of the afterglow of GRB 100621A, dedicated observations were performed in the optical/near-infrared with the 7-channel Gamma-Ray Burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPG/ESO telescope, in the sub-millimeter band with the large bolometer array LABOCA at APEX, and at radio frequencies with ATCA. Utilizing also Swift X-ray observations, we attempt an interpretation of the observational data within the fireball scenario. Results. The afterglow of GRB 100621A shows a very complex temporal and spectral evolution. We identify three different emission components, the most spectacular one causing a sudden intensity jump about one hour after the prompt emission. The spectrum of this component is much steeper than the canonical afterglow. We interpret this component using a two-shell collision prescription after the first shell has been decelerated by the circumburst medium. We use the fireball scenario to derive constraints on the microphysical parameters of the first shell. Long-term energy injection into a narrow jet seems to provide an adequate description. Another noteworthy result is the large (A V = 3.6 mag) line-of-sight host extinction of the afterglow in an otherwise extremely blue host galaxy. Conclusions. Some GRB afterglows have shown complex features, and that of GRB 100621A is another good example. Yet, detailed observational campaigns of the brightest afterglows promise to deepen our understanding of the formation of afterglows and the subsequent interaction with the circumburst medium.

Aims. We present observations aimed at exploring both the nature of Lyα emitting nebulae ("Lyα blobs") at z = 2.38 and the way they trace large scale structure (LSS), by exploring their proximity to "maximum starbursts" through submillimeter emission. Our most important objectives are to make a census of associated submillimeter galaxies (SMGs), check their properties, and look for a possible overdensity in the protocluster J2142-4426 at z = 2.38. Methods. We used the newly commissioned Large APEX Bolometer Camera (LABoCa) on the Atacama Pathfinder EXperiment (APEX) telescope, in its Science Verification phase, to carry out a deep 10 × 10 map at 870 μm, and we performed multiple checks of the quality of data processing and source extraction. Results. Our map, the first published deep image, confirms the capabilities of APEX/LABoCa as the most efficient current equipment for wide and deep submm mapping. Twenty-two sources were securely extracted with 870 μm flux densities in the range 3-21 mJy, rms noise ∼0.8-2.4 mJy, and far-IR luminosities probably in the range ∼5-20 × 10 12 L . Only one of the four 50 kpc-extended Lyα blobs has a secure 870 μm counterpart. The 870 μm source counts in the whole area are marginally higher than in the SHADES SCUBA survey, with a possible over-density around this blob. The majority of the 3.6-24 μmSEDs of the submillimeter sources indicate they are starburst dominated, with redshifts mostly 2. However, there is evidence of a high-z AGN in ∼30% of the sources.

Observations of the Sun at millimeter and submillimeter wavelengths offer a unique probe into the structure, dynamics, and heating of the chromosphere; the structure of sunspots; the formation and eruption of prominences and filaments; and energetic phenomena such as jets and flares. High-resolution observations of the Sun at millimeter and submillimeter wavelengths are challenging due to the intense, extended, lowcontrast, and dynamic nature of emission from the quiet Sun, and the extremely intense and variable nature of emissions associated with energetic phenomena. The Atacama Large Millimeter/submillimeter Array (ALMA) was designed with solar observations in mind. The requirements for solar observations are significantly different from observations of sidereal sources and special measures are necessary to successfully carry out this type of observations. We describe the commissioning efforts that enable the use of two frequency bands, the 3 mm band (Band 3) and the 1.25 mm band (Band 6), for continuum interferometric-imaging observations of the Sun with ALMA. Examples of high-resolution synthesized images obtained using the newly commissioned modes during the solar commissioning campaign held in December 2015 are presented. Although only 30 of the eventual 66 ALMA antennas were used for the campaign, the solar images synthesized from the ALMA commissioning data reveal new features of the solar atmosphere that demonstrate the potential power of ALMA solar observations. The ongoing expansion of ALMA and solar-commissioning efforts will continue to enable new and unique solar observing capabilities.