16 x 25 Ge:Ga Detector Arrays for FIFI LS

We are developing two-dimensional 16 x 25 pixel detector arrays of both unstressed and stressed Ge:Ga photoconductive detectors for far-infrared astronomy from SOFIA. The arrays, based on earlier 5 x 5 detector arrays used on the KAO, will be for our new instrument, the Far Infrared Field Imaging Line Spectrometer (FIFI LS). The unstressed Ge:Ga detector array will cover the wavelength range from 40 to 120 microns, and the stressed Ge:Ga detector array from 120 to 210 microns. The detector arrays will be operated with multiplexed integrating amplifiers with cryogenic readout electronics located close to the detector arrays. The design of the stressed detector array and results of current measurements on several prototype 16 pixel linear arrays are reported. They demonstrate the feasibility of the current concept. ***This paper does not include Figures due to astro-ph size limitations. Please download entire file at http://fifi-ls.mpe-garching.mpg.de/spie.det.ps.gz ***Comment: 8 pages, SPIE Proceedings, Astronomical Telescopes and Instrumentation 200

Observations of the rotational transitions of OH from the Orion molecular cloud

A summary of observed rotationally excited, far infrared OH line emissions from Orion-KL made using the Kuiper Airborne Observatory is given, together with a list of the resulting publications, talks, and lectures based on this data. In addition, a paper is appended, particularly addressing the (16)OH and (18)OH emission from Orion-KL. The first detections of the (16)OH (2)pi(1/2) to (2)pi(3/2) J = 3/2(-) to 3/2(+) rotational cross-ladder transition (53.351 micrometer) and the (18)OH (2)pi(3/2) J = 5/2(+) to 3/2(-) rotational ground-state transition (120.1719 micrometer). It is found that both of these lines exhibit a P-Cygni profile

Stressed detector arrays for airborne astronomy

The development of stressed Ge:Ga detector arrays for far-infrared astronomy from the Kuiper Airborne Observatory (KAO) is discussed. Researchers successfully constructed and used a three channel detector array on five flights from the KAO, and have conducted laboratory tests of a two-dimensional, 25 elements (5x5) detector array. Each element of the three element array performs as well as the researchers' best single channel detector, as do the tested elements of the 25 channel system. Some of the exciting new science possible with far-infrared detector arrays is also discussed

Physical conditions in the gas phases of the giant HII region LMC-N11 unveiled by Herschel - I. Diffuse [CII] and [OIII] emission in LMC-N11B

(Abridged) The Magellanic Clouds provide a nearby laboratory for metal-poor dwarf galaxies. The low dust abundance enhances the penetration of UV photons into the interstellar medium (ISM), resulting in a relatively larger filling factor of the ionized gas. Furthermore, there is likely a hidden molecular gas reservoir probed by the [CII]157um line. We present Herschel/PACS maps in several tracers, [CII], [OI]63um,145um, [NII]122um, [NIII]57um, and [OIII]88um in the HII region N11B in the Large Magellanic Cloud. Halpha and [OIII]5007A images were used as complementary data to investigate the effect of dust extinction. Observations were interpreted with photoionization models to infer the gas conditions and estimate the ionized gas contribution to the [CII] emission. Photodissociation regions (PDRs) are probed through polycyclic aromatic hydrocarbons (PAHs). We first study the distribution and properties of the ionized gas. We then constrain the origin of [CII]157um by comparing to tracers of the low-excitation ionized gas and of PDRs. [OIII] is dominated by extended emission from the high-excitation diffuse ionized gas; it is the brightest far-infrared line, ~4 times brighter than [CII]. The extent of the [OIII] emission suggests that the medium is rather fragmented, allowing far-UV photons to permeate into the ISM to scales of >30pc. Furthermore, by comparing [CII] with [NII], we find that 95% of [CII] arises in PDRs, except toward the stellar cluster for which as much as 15% could arise in the ionized gas. We find a remarkable correlation between [CII]+[OI] and PAH emission, with [CII] dominating the cooling in diffuse PDRs and [OI] dominating in the densest PDRs. The combination of [CII] and [OI] provides a proxy for the total gas cooling in PDRs. Our results suggest that PAH emission describes better the PDR gas heating as compared to the total infrared emission.Comment: Accepted for publication in Astronomy and Astrophysics. Fixed inverted line ratio in Sect. 5.

CEA Bolometer Arrays: the First Year in Space

The CEA/LETI and CEA/SAp started the development of far-infrared filled bolometer arrays for space applications over a decade ago. The unique design of these detectors makes possible the assembling of large focal planes comprising thousands of bolometers running at 300 mK with very low power dissipation. Ten arrays of 16x16 pixels were thoroughly tested on the ground, and integrated in the Herschel/PACS instrument before launch in May 2009. These detectors have been successfully commissioned and are now operating in their nominal environment at the second Lagrangian point of the Earth-Sun system. In this paper we briefly explain the functioning of CEA bolometer arrays, and we present the properties of the detectors focusing on their noise characteristics, the effect of cosmic rays on the signal, the repeatability of the measurements, and the stability of the system

Spectroscopic FIR mapping of the disk and galactic wind of M82 with Herschel-PACS

[Abridged] We present maps of the main cooling lines of the neutral atomic gas ([OI] at 63 and 145 micron and [CII] at 158 micron) and in the [OIII] 88 micron line of the starburst galaxy M82, carried out with the PACS spectrometer on board the Herschel satellite. By applying PDR modeling we derive maps of the main ISM physical parameters, including the [CII] optical depth, at unprecedented spatial resolution (~300 pc). We can clearly kinematically separate the disk from the outflow in all lines. The [CII] and [OI] distributions are consistent with PDR emission both in the disk and in the outflow. Surprisingly, in the outflow, the atomic and the ionized gas traced by the [OIII] line both have a deprojected velocity of ~75 km/s, very similar to the average velocity of the outflowing cold molecular gas (~ 100 km/s) and several times smaller than the outflowing material detected in Halpha (~ 600 km/s). This suggests that the cold molecular and neutral atomic gas and the ionized gas traced by the [OIII] 88 micron line are dynamically coupled to each other but decoupled from the Halpha emitting gas. We propose a scenario where cold clouds from the disk are entrained into the outflow by the winds where they likely evaporate, surviving as small, fairly dense cloudlets (n_H\sim 500-1000 cm^-3, G_0\sim 500- 1000, T_gas\sim300 K). We show that the UV photons provided by the starburst are sufficient to excite the PDR shells around the molecular cores. The mass of the neutral atomic gas in the outflow is \gtrsim 5-12x 10^7 M_sun to be compared with that of the molecular gas (3.3 x 10^8 M_sun) and of the Halpha emitting gas (5.8 x 10^6 M_sun). The mass loading factor, (dM/dt)/SFR, of the molecular plus neutral atomic gas in the outflow is ~ 2. Energy and momentum driven outflow models can explain the data equally well, if all the outflowing gas components are taken into account.Comment: 26 pages, 23 figures, 4 Tables, Accepted for publication in Astronomy & Astrophysic

Herschel PACS Spectroscopic Diagnostics of Local ULIRGs: Conditions and Kinematics in Mrk 231

In this first paper on the results of our Herschel PACS survey of local Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of local galaxies, we present far-infrared spectroscopy of Mrk 231, the most luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the first time in a ULIRG, all observed far-infrared fine-structure lines in the PACS range were detected and all were found to be deficient relative to the far infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity galaxies. The deficits are similar to those for the mid-infrared lines, with the most deficient lines showing high ionization potentials. Aged starbursts may account for part of the deficits, but partial covering of the highest excitation AGN powered regions may explain the remaining line deficits. A massive molecular outflow, discovered in OH and 18OH, showing outflow velocities out to at least 1400 km/sec, is a unique signature of the clearing out of the molecular disk that formed by dissipative collapse during the merger. The outflow is characterized by extremely high ratios of 18O / 16O suggestive of interstellar medium processing by advanced starbursts.Comment: Accepted for publication in the Astronomy and Astrophysics Herschel Special Issue, 5 pages, 4 figure

The 158 micron (CII) mapping of galaxies: Probing the atomic medium

Using the MPE/UCB Far-infrared Imaging Fabry-Perot Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO), we have made large scale maps of (CII) in the spiral galaxies NGC 6946, NGC 891, M83 and the peculiar elliptical Cen A, thus allowing for the first time, detailed studies of the spatial distribution of the FIR line emission in external galaxies. We find that the (CII) emission comes from a mixture of components of interstellar gas. The brightest emission is associated with the nuclear regions, a second component traces the spiral arms as seen in the nearly face on spiral galaxies NGC 6946 and M83 and the largest star forming/H2 regions contained within them, and another extended component of low brightness can be detected in all of the galaxies far from the nucleus, beyond the extent of CO emission

A deep Herschel/PACS observation of CO(40-39) in NGC 1068: a search for the molecular torus

Emission from high-J CO lines in galaxies has long been proposed as a tracer of X-ray dominated regions (XDRs) produced by AGN. Of particular interest is the question of whether the obscuring torus, which is required by AGN unification models, can be observed via high-J CO cooling lines. Here we report on the analysis of a deep Herschel-PACS observation of an extremely high J CO transition (40-39) in the Seyfert 2 galaxy NGC 1068. The line was not detected, with a derived 3$\sigma$ upper limit of $2 \times 10^{-17}\,\text{W}\,\text{m}^{-2}$. We apply an XDR model in order to investigate whether the upper limit constrains the properties of a molecular torus in NGC 1068. The XDR model predicts the CO Spectral Line Energy Distributions for various gas densities and illuminating X-ray fluxes. In our model, the CO(40-39) upper limit is matched by gas with densities $\sim 10^{6}-10^{7}\,\text{cm}^{-3}$, located at $1.6-5\,\text{pc}$ from the AGN, with column densities of at least $10^{25}\,\text{cm}^{-2}$. At such high column densities, however, dust absorbs most of the CO(40-39) line emission at $\lambda = 65.69\, \mu$m. Therefore, even if NGC 1068 has a molecular torus which radiates in the CO(40-39) line, the dust can attenuate the line emission to below the PACS detection limit. The upper limit is thus consistent with the existence of a molecular torus in NGC 1068. In general, we expect that the CO(40-39) is observable in only a few AGN nuclei (if at all), because of the required high gas column density, and absorption by dust.Comment: 22 pages, accepted for publication in Ap

The Far-Infrared, UV and Molecular Gas Relation in Galaxies up to z=2.5

We use the infrared excess (IRX) FIR/UV luminosity ratio to study the relation between the effective UV attenuation (A_IRX) and the UV spectral slope (beta) in a sample of 450 1<z<2.5 galaxies. The FIR data is from very deep Herschel observations in the GOODS fields that allow us to detect galaxies with SFRs typical of galaxies with log(M)>9.3. Thus, we are able to study galaxies on and even below the main SFR-stellar mass relation (main sequence). We find that main sequence galaxies form a tight sequence in the IRX--beta plane, which has a flatter slope than commonly used relations. This slope favors a SMC-like UV extinction curve, though the interpretation is model dependent. The scatter in the IRX-beta plane, correlates with the position of the galaxies in the SFR-M plane. Using a smaller sample of galaxies with CO gas masses, we study the relation between the UV attenuation and the molecular gas content. We find a very tight relation between the scatter in the IRX-beta plane and the specific attenuation (S_A), a quantity that represents the attenuation contributed by the molecular gas mass per young star. S_A is sensitive to both the geometrical arrangement of stars and dust, and to the compactness of the star forming regions. We use this empirical relation to derive a method for estimating molecular gas masses using only widely available integrated rest-frame UV and FIR photometry. The method produces gas masses with an accuracy between 0.12-0.16 dex in samples of normal galaxies between z~0 and z~1.5. Major mergers and sub-millimeter galaxies follow a different S_A relation.Comment: 11 pages, 6 pages appendix, 11 figures, accepted to Ap