LSDCat: Detection and cataloguing of emission-line sources in integral-field spectroscopy datacubes

We present a robust, efficient, and user-friendly algorithm for detecting faint emission-line sources in large integral-field spectroscopic datacubes together with the public release of the software package LSDCat (Line Source Detection and Cataloguing). LSDCat uses a 3-dimensional matched filter approach, combined with thresholding in signal-to-noise, to build a catalogue of individual line detections. In a second pass, the detected lines are grouped into distinct objects, and positions, spatial extents, and fluxes of the detected lines are determined. LSDCat requires only a small number of input parameters, and we provide guidelines for choosing appropriate values. The software is coded in Python and capable to process very large datacubes in a short time. We verify the implementation with a source insertion and recovery experiment utilising a real datacube taken with the MUSE instrument at the ESO Very Large Telescope.Comment: 14 pages. Accepted for publication in Astronomy & Astrophysics. The LSDCat software is available at https://bitbucket.org/Knusper2000/lsdcat, v2 corrected typos and language editin

Physical Properties of Arctic and Antarctic Aerosol Particles and Cloud Condensation Nuclei

Aerosol Partikel interagieren mit solarer und terrestrischer Strahlung durch Absorption und Streuung. Zusätzlich bilden und modifizieren sie die Eigenschaften von Wolken da sie das Potential besitzen als Wolkenkondensationskeim (CCN) fungieren zu können und stellen somit eine wichtige Komponente im Klimasystem dar. Die Eigenschaften von Partikeln und CCN müssen genaustens bekannt sein um deren Einfluss in Klima- und Strahlungsmodellen akurat berücksichtigen zu können. Ziel dieser Arbeit ist die Charakterisierung der Partikeleigenschaften in Regionen, welche das Klima maßgeblich beeinflussen, wie die Arktis und die Antarktis. Im Rahmen dieser Arbeit wurden 2 Datensätze aufgenommen, welche helfen das Verständnis über Partikel und CCN im Frühjar und Sommer in der Arktis und Antarktis zu verbessern. Es wurden jeweils die Gesamt- und die CCN-Anzahlkonzentration (NCN, NCCN), die Anzahlgrößenverteilung (PNSD) und der Hygroskopizitätsparameter (k) der Partikel bestimmt. Die Herkunft der vermessenen Partikel wurde mit Rückwärtstrajektorien ermittelt sowie weitere Analysen bezüglich der Verweilzeiten durchgeführt. Beide Datensätze zeigen, dass eine starke Abhängigkeit der Partikel- und CCN-Eigenschaften vom Luftmassenursprung vorliegt. Zeigen arktische PNSDs nur eine Akkumulationsmode, konnte diese auf gealtertes Aerosol mit einem eurasischen Ursprung zurückgeführt werden. Kommt eine zweite Mode mit kleineren Partikeln hinzu, wurde der Nord-Pazifische Raum als Ursprung bestimmt. In der Antarktis wurde besonders für NCN und NCCN eine starke Abhängigkeit vom Luftmassenursprung gefunden. Dabei konnten mit der Anwendung des Dispersionsmodells NAME Antarktische Hintergrundkonzentrationen ermittelt werden. Weiterhin wurde gefunden, dass Antarktische Aerosolpartikel mit einem k von 1 hygroscopischer als das Arktische ist, für welches ein k von 0,19 bestimmt wurde. Zusätzlich durchgeführte Flugzeugmessungen über Tuktoyaktuk (Arktis) zeigen, dass die Messungen am Boden auch repräsentativ für die Grenzschicht sind. Die Schichten über der Grenzschicht scheinen jedoch von dieser entkoppelt zu sein und es wird vermutet, dass der Ursprung der Partikel in größeren Höhen in niedrigeren geographischen Breiten liegt.:Contents List of Abbreviations iii List of Symbols v 1. Introduction 1 2. Experimental 9 2.1. Measured Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1. Total Particle Number Concentration . . . . . . . . . . . . . . . 9 2.1.2. Particle Number Size Distribution . . . . . . . . . . . . . . . . . 10 2.1.3. Total Concentration of Cloud Condensation Nuclei . . . . . . . . 15 2.2. Determination of the CCN hygroscopicity . . . . . . . . . . . . . . . . . 16 2.2.1. Köhler theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.2. The hygroscopicity parameter k and the critical diameter dcrit . . 18 2.3. Determination of the Air Mass Origin . . . . . . . . . . . . . . . . . . . 20 2.3.1. The NAME Dispersion Model . . . . . . . . . . . . . . . . . . . 20 2.3.2. Potential Source Contribution Function . . . . . . . . . . . . . . 22 3. Results and Discussion 25 3.1. Measurements of aerosol and CCN properties in the Mackenzie River delta (Canadian Arctic) during Spring-Summer transition in May 2014 . . 25 3.1.1. Campaign overview . . . . . . . . . . . . . . . . . . . . . . . . 25 3.1.2. Overview of NCN, NCCN and PNSD data for the entire measurement period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.1.3. Identification of air mass origins and potential source regions . . . 32 3.1.4. PNSD of the three periods . . . . . . . . . . . . . . . . . . . . . 35 3.1.5. Critical diameter dcrit and hygroscopicity parameter k . . . . . . 38 3.1.6. Comparison of height resolved airborne and ground based PNSDs 41 3.2. Measurements of aerosol and CCN properties at the Princess Elisabeth Antarctica Research Station during three austral summers . . . . . . . . . 45 3.2.1. Campaign overview . . . . . . . . . . . . . . . . . . . . . . . . 45 3.2.2. Total Particle and CCN number concentrations and regional analysis of the NAME model footprints . . . . . . . . . . . . . . . . 50 3.2.3. PSCF results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.2.4. Hygroscopicity . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4. Summary, Conclusions and Outlook 65 A. Appendix 71 A.1. SS calibration of the CCNC . . . . . . . . . . . . . . . . . . . . . . . . . 71 A.2. Error Analysis with Monte Carlo Simulation . . . . . . . . . . . . . . . . 73 B List of Figures vii C List of Tables viii Bibliography xiAtmospheric aerosol particles interact with solar and terrestrial radiation by absorption and scattering. Further, they have the potential to act as cloud condensation nuclei (CCN) and to form and modify the radiative properties of clouds and thus are an important component in the Earth’s climate system. An accurate knowledge about the aerosol particle and CCN properties is very important for accurate climate and radiation models. The objective of this thesis is the characterization of aerosol particles in regions that are key regulators of the Earth’s climate. The Arctic and the Antarctic are such regions. Hence, in the framework of this doctoral thesis two data sets were recorded, that help gaining further knowledge about the spring and summer time aerosol particles and CCN in the Arctic and Antarctic region. For both, the Arctic and the Antarctic aerosol population, the CCN and the total particle number concentration (NCCN, NCN), the particle number size distribution (PNSD) and the hygroscopicity parameter k were determined. The history of the measured air masses was explored using back trajectories and residence time analysis. For both examined regions, a strong influence of the air mass origin on the aerosol particle and CCN properties was found. The PNSDs measured in the Arctic were found to be mono-modal showing an accumulation mode which most likely contains well aged particles that have an Eurasian origin. Bi-modal PNSDs with an additional mode of smaller particles were found to originate from the Northern Pacific. In the Antarctic the air mass origin was found to significantly influence NCCN and NCN. With the application of the NAME dispersion model Antarctic continental background concentrations could be determined. With k values of 1 the Antarctic aerosol was found to be much more hygroscopic than the Arctic aerosol, for which a k of 0.19 was determined. Additional Arctic aircraft measurements show that ground based measurements are representative for the Arctic boundary layer. However particles above the boundary layer seem to be decoupled from lower layers and were believed to be advected from lower latitudes in different height layers and mixed down in the lower Arctic troposphere.:Contents List of Abbreviations iii List of Symbols v 1. Introduction 1 2. Experimental 9 2.1. Measured Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1. Total Particle Number Concentration . . . . . . . . . . . . . . . 9 2.1.2. Particle Number Size Distribution . . . . . . . . . . . . . . . . . 10 2.1.3. Total Concentration of Cloud Condensation Nuclei . . . . . . . . 15 2.2. Determination of the CCN hygroscopicity . . . . . . . . . . . . . . . . . 16 2.2.1. Köhler theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.2. The hygroscopicity parameter k and the critical diameter dcrit . . 18 2.3. Determination of the Air Mass Origin . . . . . . . . . . . . . . . . . . . 20 2.3.1. The NAME Dispersion Model . . . . . . . . . . . . . . . . . . . 20 2.3.2. Potential Source Contribution Function . . . . . . . . . . . . . . 22 3. Results and Discussion 25 3.1. Measurements of aerosol and CCN properties in the Mackenzie River delta (Canadian Arctic) during Spring-Summer transition in May 2014 . . 25 3.1.1. Campaign overview . . . . . . . . . . . . . . . . . . . . . . . . 25 3.1.2. Overview of NCN, NCCN and PNSD data for the entire measurement period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.1.3. Identification of air mass origins and potential source regions . . . 32 3.1.4. PNSD of the three periods . . . . . . . . . . . . . . . . . . . . . 35 3.1.5. Critical diameter dcrit and hygroscopicity parameter k . . . . . . 38 3.1.6. Comparison of height resolved airborne and ground based PNSDs 41 3.2. Measurements of aerosol and CCN properties at the Princess Elisabeth Antarctica Research Station during three austral summers . . . . . . . . . 45 3.2.1. Campaign overview . . . . . . . . . . . . . . . . . . . . . . . . 45 3.2.2. Total Particle and CCN number concentrations and regional analysis of the NAME model footprints . . . . . . . . . . . . . . . . 50 3.2.3. PSCF results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.2.4. Hygroscopicity . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4. Summary, Conclusions and Outlook 65 A. Appendix 71 A.1. SS calibration of the CCNC . . . . . . . . . . . . . . . . . . . . . . . . . 71 A.2. Error Analysis with Monte Carlo Simulation . . . . . . . . . . . . . . . . 73 B List of Figures vii C List of Tables viii Bibliography x

Where is the fuzz? Undetected Lyman alpha nebulae around QSOs at z~2.3

We observed a small sample of 5 radio-quiet QSOs with integral field spectroscopy to search for possible extended emission in the Ly$\alpha$ line. We subtracted the QSO point sources using a simple PSF self-calibration technique that takes advantage of the simultaneous availability of spatial and spectral information. In 4 of the 5 objects we find no significant traces of extended Ly$\alpha$ emission beyond the contribution of the QSO nuclei itself, while in UM 247 there is evidence for a weak and spatially quite compact excess in the Ly$\alpha$ line at several kpc outside the nucleus. For all objects in our sample we estimated detection limits for extended, smoothly distributed Ly$\alpha$ emission by adding fake nebulosities into the datacubes and trying to recover them after PSF subtraction. Our observations are consistent with other studies showing that giant Ly$\alpha$ nebulae such as those found recently around some quasars are very rare. Ly$\alpha$ fuzz around typical radio-quiet QSOs is fainter, less extended and is therefore much harder to detect. The faintness of these structures is consistent with the idea that radio-quiet QSOs typically reside in dark matter haloes of modest masses.Comment: 12 Pages, Accepted for publication in A&

The Milky Way halo as a QSO absorption-line system. New results from an HST/STIS absorption-line catalogue of Galactic high-velocity clouds

We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering fractions of low- and intermediate ions (OI, CII, SiIII, MgII, FeII, SiIII, CIV, and SiIV) in the range fc = 0.20 - 0.70. For detailed analysis we concentrate on SiII absorption components in HVCs, for which we investigate the distribution of column densities, b-values, and radial velocities. Combining information for SiII and MgII, and using a geometrical HVC model we investigate the contribution of HVCs to the absorption cross section of strong MgII absorbers in the local Universe. We estimate that the Galactic HVCs would contribute on average ~52 % to the total strong MgII cross section of the Milky Way, if our Galaxy were to be observed from an exterior vantage point. We further estimate that the mean projected covering fraction of strong MgII absorption in the Milky Way halo and disc from an exterior vantage point is fc(sMgII) = 0.31 for a halo radius of R = 61 kpc. These numbers, together with the observed number density of strong MgII absorbers at low redshift, indicate that the contribution of infalling gas clouds (i.e., HVC analogues) in the halos of Milky Way-type galaxies to the cross section of strong MgII absorbers is <34 %. These findings are in line with the idea that outflowing gas (e.g., produced by galactic winds) in the halos of more actively star-forming galaxies dominate the absorption-cross section of strong MgII absorbers in the local Universe

An IFU investigation of possible Lyman continuum escape from Mrk 71/NGC 2366

Mrk 71/NGC 2366 is the closest Green Pea (GP) analog and candidate Lyman Continuum (LyC) emitter. Recently, 11 LyC-leaking GPs have been detected through direct observations of the ionizing continuum, making this the most abundant class of confirmed LyC-emitters at any redshift. High resolution, multi-wavelength studies of GPs can lead to an understanding of the method(s), through which LyC escapes from these galaxies. The proximity of Mrk 71/NCG 2366 offers unprecedented detail on the inner workings of a GP analog, and enables us to identify the mechanisms of LyC escape. We use 5825-7650{\AA} integral field unit PMAS observations to study the kinematics and physical conditions in Mrk 71. An electron density map is obtained from the [S II] ratio. A fortuitous second order contamination by the [O II]3727 doublet enables the construction of an electron temperature map. Resolved maps of sound speed, thermal broadening, "true" velocity dispersion, and Mach number are obtained and compared to the high resolution magneto-hydrodynamic SILCC simulations. Two regions of increased velocity dispersion indicative of outflows are detected to the north and south of the super star cluster, knot B, with redshifted and blueshifted velocities, respectively. We confirm the presence of a faint broad kinematical component, which is seemingly decoupled from the outflow regions, and is fainter and narrower than previously reported in the literature. Within uncertainties, the low- and high-ionization gas move together. Outside of the core of Mrk 71, an increase in Mach numbers is detected, implying a decrease in gas density. Simulations suggest this drop in density can be as high as ~4 dex, down to almost optically thin levels, which would imply a non-zero LyC escape fraction along the outflows... [abridged]Comment: Accepted for publication in A&A. 17 pages, 16 figures, 4 table

Super star cluster feedback driving ionization, shocks and outflows in the halo of the nearby starburst ESO 338-IG04

Stellar feedback strongly affects the interstellar medium (ISM) of galaxies. Stellar feedback in the first galaxies likely plays a major role in enabling the escape of LyC photons, which contribute to the re-ionization of the Universe. Nearby starburst galaxies serve as local analogues allowing for a spatially resolved assessment of the feedback processes in these galaxies. We characterize the feedback effects from the star clusters in the local high-redshift analogue ESO 338-IG04 on the ISM and compare the results with the properties of the most massive clusters. We use high quality VLT/MUSE optical integral field data to derive the physical properties of the ISM such as ionization, density, shocks, and perform new fitting of the spectral energy distributions of the brightest clusters in ESO 338-IG04 from HST imaging. ESO 338-IG04 has a large ionized halo which we detect to a distance of 9 kpc. We identify 4 Wolf-Rayet (WR) clusters based on the blue and red WR bump. We follow previously identified ionization cones and find that the ionization of the halo increases with distance. Analysis of the galaxy kinematics shows two complex outflows driven by the numerous young clusters in the galaxy. We find a ring of shocked emission traced by an enhanced [OI]/H$\alpha$ ratio surrounding the starburst and at the end of the outflow. Finally we detect nitrogen enriched gas associated with the outflow, likely caused by the WR stars in the massive star clusters. Photo-ionization dominates the central starburst and sets the ionization structure of the entire halo, resulting in a density bounded halo, facilitating the escape of LyC photons. Outside the central starburst, shocks triggered by an expanding super bubble become important. The shocks at the end of the outflow suggest interaction between the hot outflowing material and the more quiescent halo gas.Comment: Accepted for publication in Astronomy and Astrophysics, 22 pages, 15 figure

An HST/COS legacy survey of intervening SiIII absorption in the extended gaseous halos of low-redshift galaxies

Doubly ionized silicon (SiIII) is a powerful tracer of diffuse ionized gas inside and outside of galaxies. It can be observed in the local Universe in ultraviolet (UV) absorption against bright extragalactic background sources. We here present an extensive study of intervening SiIII-selected absorbers and their relation to the circumgalactic medium (CGM) of galaxies at low redshift (z<=0.1), based on the analysis of UV absorption spectra along 303 extragalactic lines of sight obtained with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST). Along a total redshift path of Dz=24 we identify 69 intervening SiIII systems that all show associated absorption from other low and high ions. We derive a bias-corrected number density of dN/dz(SiIII)=2.5 for absorbers with column densities log N(SiIII)>12.2. We develop a geometrical model for the absorption-cross section of the CGM around the local galaxy population and find excellent agreement between the model predictions and the observations. We further compare redshifts and positions of the absorbers with that of ~64,000 galaxies using archival galaxy-survey data. For the majority of the absorbers we identify possible host galaxies within 300 km/s of the absorbers and derive impact parameters rho<200 kpc, demonstrating that the spatial distributions of SiIII absorbers and galaxies are highly correlated. Our study indicates that the majority of SiIII-selected absorbers in our sample trace the CGM of nearby galaxies within their virial radii at a typical covering fraction of ~70 per cent. From a detailed ionization model we estimate that diffuse gas in the CGM around galaxies, as traced by SiIII, contains substantially more baryonic mass than their neutral interstellar medium.Comment: 32 pages, 17 figures; final version accepted for publication in A&

MUSE Illuminates Channels for Lyman Continuum Escape in the Halo of SBS 0335-52E

We report on the discovery of ionised gas filaments in the circum-galactic halo of the extremely metal-poor compact starburst SBS 0335-052E in a 1.5h integration with the MUSE integral-field spectrograph. We detect these features in H${\alpha}$ and [OIII] emission down to surface-brightness levels of $5 \times 10^{-19}$erg s$^{-1}$cm$^{-2}$arcsec$^{-2}$. The filaments have projected diameters of 2.1 kpc and extend more than 9 kpc to the north and north-west from the main stellar body. We also detect extended nebular HeII $\lambda$4686 emission that brightens towards the north-west at the rim of a star-burst driven super-shell, suggestive of a locally enhanced UV radiation field due to shocks. We also present a velocity field of the ionised gas. The filaments appear to connect seamlessly in velocity space to the kinematical disturbances caused by the shell. Similar to high-$z$ star-forming galaxies, the ionised gas in this galaxy is dispersion dominated. We argue that the filaments were created via feedback from the starburst and that these ionised structures in the halo may act as escape channels for Lyman continuum radiation in this gas-rich system.Comment: Revised version after peer review. Accepted for publication in A&A letter

Deciphering Lyman α\alpha blob 1 with deep MUSE observations

Context: Lyman $\alpha$ blobs (LABs) are large-scale radio-quiet Lyman $\alpha$ (Ly$\alpha$) nebula at high-$z$ that occur predominantly in overdense proto-cluster regions. Especially the prototypical SSA22a-LAB1 at $z=3.1$ has become an observational reference for LABs across the electromagnetic spectrum. Aims: We want to understand the powering mechanisms that drive the LAB to gain empirical insights into galaxy formation processes within a rare dense environment at high-$z$. Methods: LAB 1 was observed for 17.5h with the VLT/MUSE integral-field spectrograph. We produced optimally extracted narrow band images in Ly$\alpha$ $\lambda1216$ and HeII $\lambda1640$. By using a moment based analysis we mapped the kinematics of the blob. Results: We detect Ly$\alpha$ emission to surface-brightness limits of $10^{-19}$erg s$^{-1}$cm$^{-2}$arcsec$^{-2}$. At this depth we reveal a bridge between LAB 1 and its northern neighbour LAB 8, as well as a shell-like filament towards the south of LAB 1. We find a coherent large scale east-west $\sim$1000 km s$^{-1}$ velocity gradient that is aligned perpendicular to the major axis of the blob. We detect HeII emission in three distinct regions, but we can only provide upper limits for CIV. Conclusions: Various gas excitation mechanisms are at play in LAB 1: Ionising radiation and feedback effects dominate near the embedded galaxies, while Ly$\alpha$ scattering is contributing at larger distances. However, HeII/Ly$\alpha$ ratios combined with upper limits on CIV/Ly$\alpha$ can not discriminate between AGN ionisation and feedback driven shocks. The alignment of the angular momentum vector parallel to the morphological principal axis appears odds with the predicted norm for high-mass halos, but likely reflects that LAB\,1 resides at a node of multiple intersecting filaments of the cosmic web. (Abridged)Comment: Revised version. Accepted for publication in A&