2D spectroscopy in astronomy

Abstract. 2D-spectroscopy in astronomy is defined as a technique where a spatially resolved electromagnetic spectrum is obtained over a two-dimensional field. In this paper the very basic principles of spectroscopy are briefly covered starting from the single slit concept via the Huygens principle and the Fraunhofer diffraction. The basic concept of a grating-based spectrograph is described. The connection between observed spectra, the chemical footprints and the underlying physical properties of the systems are briefly covered. The main IFU techniques used in the field of integral field spectroscopy are introduced. The basic ideas on how the data from the observed targets are produced and the wanted physical properties from the data are recovered are discussed. The work demonstrates the usage of 2D-spectroscopic data and its usefulness. The decay in the velocity dispersion profiles in the near central regions of galaxies known as sigma-drop is briefly introduced and a sample of 13 galaxies hosting a possible sigma-drop is analyzed via elliptical apertures. The radial profiles of each galaxy are extracted from given 2D-data connected to the kinematics of the sample galaxies. The radial profiles are then graphically presented with kinematic maps corresponding to the rotation velocity, the velocity dispersion, h₄ and h₃ profiles of the galaxy. Here the h₄ and h₃ are the amplitudes of the Gauss-Hermite series corresponding to the symmetric and asymmetric deviation from a Gaussian. The sample consists of only barred galaxies which could indicate star formation caused sigma-drops due to the bar-driven inflow of the gas to the central regions of the galaxies. Well-defined dust lanes are seen in ~70% of the sample showing a possible relation between the dust and the sigma-drops. There is no direct connection observed between the sigma-drops and the sizes of the galaxies

Integral field spectroscopy:a glance to chemo-dynamics in galaxies

Abstract. 3D information of the structures in galaxies is not directly available from the morphologies that are, however, needed to target studies on the structures. Alternatively, the spectra of galaxies broadened by the line-of-sight-velocity-distribution (LOSVD) can be used as LOS spatial distribution probes and hold the chemical footprints left along the evolution of galaxies. Knowledge gained from the density distributions and the stellar populations narrows down the processes involved in building these observed morphologies. Integral field spectroscopy (IFS) is an ideal technique for such cases as it instantaneously provides simultaneous morphological and spectral information from the targets. Thick disks and X/B/P bulges are both structures that are often most directly observable in a near edge-on orientation. The vertical density distribution in these structures are the result of evolutional processes that produce stellar populations accordingly but direct information on the distribution vanishes sharply with decreasing inclination ($i$) as does our consensus of the structures in the LOS. Investigating such structures and the LOSVDs in simulations can lift some of the doubt and improve our knowledge to be adapted on the search of these structures over various galaxy inclinations. In this thesis Gauss-Hermite series are deployed to scrutinise the LOSVDs in thin-thick disk and X/B/P simulations (A and B) against the IFS data from central regions of 13 ($\textrm{SA-S}\underline{\textrm{A}}\textrm{B}$) galaxies with $\langle M_{*}\rangle \approx 2\times10^{10.5}\textrm{M}_{\odot}$, $\langle T \rangle \approx 2$, $\langle i \rangle \approx 45°$ from the Spitzer Survey Stellar Structures in Galaxies ($\mathrm{S}^{4}\mathrm{G}$) sample. Thin-thick disk superposition in simulation-A produces radially increasing amplitudes of the fourth Gauss-Hermite moment ($h_{4}$). The third Gauss-Hermite moment ($h_{3}$) shows mainly anti-correlation with LOSV and persist relatively strong even for low inclinations. These signatures are observed in the IFS data but due to limited field-of-view (FoV) and on-plane rings observed in the systems they are not unambiguous. In simulation-B, negative $h_{4}$ minima are found on average at $r \approx 2h_{r}$ and corresponds to the X-shape structure on edge-on view. Regarding observations, the nuclear region also highlights a $h_{4}$-ring that is a signature observed frequently in the sample. In simulation-B the $h_{4}$ ring is produced by the disk-bulge superposition in the LOS and is observable independent of inclination. NGC 1068 and NGC 1387 are found to be X/B/P bulge candidates as both are observed in low $i$, in which the fourth vertical density distribution moment ($d_{4}$) is probed by the $h_{4}$ moment, and are observed with negative $h_{4}$ at a radial distance $h_{r} \lt r \lt 2h_{r}$. In low $i$ the $h_{4}$ minima in simulation-B are found with weak $h_{3}-V$ correlation that is observed with NGC 1387 but not clearly with NGC 1068.2D spektroskopia : katsaus galaksien kemo-dynamiikkaan. Tiivistelmä. 3D informaatio galaksien rakenteista ei ole suoraan havaittavissa niiden morfologiasta, jota kuitenkin tarvitaan näiden rakenteiden tutkimiseen. Toisaalta galaksien spektrit laajentuessaan katseen suuntaisten nopeusjakaumien (LOSVD) mukaisesti mahdollistavat rakenteiden syvyyssuuntaisen ulottuvuuden tutkimisen ja pitävät sisällään kemialliset jalanjäljet galaksien evoluutiosta. Tiheys/nopeusjakaumista ja tähtipopulaatiosta saatava tieto tuottaa tarkemman kuvan siitä, mitkä prosessit kykenevät muodostamaan galakseissa havaitut rakenteet. 2D-spektroskopia (IFS) on ideaali keino galaksien rakenteiden tutkimiseen sen välittömästi tuottaman yhtäaikaisen morfologisen ja spektroskooppisen informaation ansiosta. Paksukiekot ja X/B/P keskuspullistumat ovat rakenteita, jotka ovat usein havaittavissa suuren inklinaation omaavissa galakseissa. Näiden rakenteiden pystysuuntaiset tiheys/nopeusjakaumat ja tähtipopulaatiot ovat evoluutionaalisten prosessien tulosta, mutta havaittavan galaksin inklinaation ollessa pieni, suora informaatio rakenteiden pystysuuntaisista tiheysjakaumista ja identiteetistä katoaa. Siksi rakenteiden muodon ja niiden katseen suuntaisten nopeushajontojen tutkiminen simulaatiossa vahvistaa käsitystämme galakseissa esiintyvistä rakenteista. Työssä hyödynnetään Gauss-Hermite sarjoja nopeusjakaumien analyysiin kahdessa simulaatiossa ja 2D spektroskopiassa 13:lle ($\textrm{SA-S}\underline{\textrm{A}}\textrm{B}$) galaksille ($\langle M_{*}\rangle \approx 2\times10^{10.5}\textrm{M}_{\odot}$, $\langle T \rangle \approx 2$, $\langle i \rangle \approx 45°$) ”Spitzer Survey of Stellar Structures in Galaxies (S4G)” havaintojoukosta. Kaksoiskiekkosimulaatiossa kiekkojen superpositio-LOSVD tuottaa radiaalisesti ulospäin kasvavan Gauss-Hermite sarjan neljännen momentin ($h_{4}$). Gauss-Hermite sarjan kolmas momentti ($h_{3}$) anti-korreloi LOSV kanssa ja on havaittavissa suhteellisen selvästi, myös matalilla simulaatio inklinaatiolla. Vastaavat merkit ovat havaittavissa IFS datasta, mutta rajallisesta havaintoalueesta ja häiriöitä tuottavista rengasrakenteista johtuen ne eivät ole yksiselitteisiä. X/B/P simulaatiossa negatiiviset $h_{4}$ minimit esiintyvät keskimäärin etäisyydellä $r \approx 2h_{r}$, joka vastaa X-rakennetta kylki-edessä orientaatiossa. Simulaation keskustassa havaitaan keskuspullistuman ja kiekon tuottama $h_{4}$ rengas, joka on usein esiintyvä piirre havaintojoukon IFS datassa. NGC 1068 ja NGC 1387 ovat X/B/P keskuspullistuma kandidaatteja, sillä molemmat ovat inklinaatiossa, jossa vertikaalisen tiheysjakauman neljännen momentin ($d_{4}$) tulkinta $h_{4}$ arvoista on mahdollista ja molemmissa tapauksissa negatiiviset $h_{4}$ minimit löytyvät radiaalisella etäisyydellä $h_{r} \lt r \lt 2h_{r}$. Matalilla inklinaatiolla simulaation $h_{4}$ minimit havaitaan heikon $h_{3}-V$ korrelaation kanssa, joka on havaittavissa NGC 1387:ssä, mutta ei selkeästi NGC 1068:ssa

Dynamics of fracture in dissipative systems

Dynamics of fracture in two-dimensional systems is studied with a dissipative network model by including the local relaxation of the force field via Maxwellian viscoelasticity. In addition to disorder the fundamentals of crack formation and propagation depend on the strength of dissipation compared to the loading rate. We investigate the dynamics of a single crack and the role of stress reduction at the crack tip when dissipation is increased. As a consequence, the crack starts to propagate slowly and it reaches terminal velocity later. If the relaxation of local forces is strong enough compared with crack velocity, crack arrest takes place. For a disordered system, the presence of strong dissipation in local dynamics is reflected as ductility and as an increase in the damage, accumulated during the fracture process.Peer reviewe

Dissipative dynamic fracture of disordered systems

Breakdown of two-dimensional disordered systems is studied with a time-dependent network model. The dependence of fracture process on the local relaxation of the force field is included within the framework of Maxwellian viscoelasticity. The dynamics and characteristics of crack formation and propagation are shown to depend on disorder and relative time scales of dissipation and loading. Brittle behavior is encountered in the adiabatic limit of slow straining. At finite strain rates, the development of damage shows ductile behavior with increasing dissipation. Nucleation of cracks in various dynamical situations is discussed.Peer reviewe

Ice Age Epochs and the Sun's Path Through the Galaxy

We present a calculation of the Sun's motion through the Milky Way Galaxy over the last 500 million years. The integration is based upon estimates of the Sun's current position and speed from measurements with Hipparcos and upon a realistic model for the Galactic gravitational potential. We estimate the times of the Sun's past spiral arm crossings for a range in assumed values of the spiral pattern angular speed. We find that for a difference between the mean solar and pattern speed of Omega_Sun - Omega_p = 11.9 +/- 0.7 km/s/kpc the Sun has traversed four spiral arms at times that appear to correspond well with long duration cold periods on Earth. This supports the idea that extended exposure to the higher cosmic ray flux associated with spiral arms can lead to increased cloud cover and long ice age epochs on Earth.Comment: 14 pages, 3 figures, accepted for publication in Ap

Reflectance properties of selected arctic-boreal land cover types: field measurements and their application in remote sensing

International audienceWe developed a mobile remote sensing measurement facility for spectral and anisotropic reflectance measurements. We measured reflection properties (BRF) of over 100 samples from most common land cover types in boreal and subarctic regions. This extensive data set serves as a unique reference opportunity for developing interpretation algorithms for remotely sensed materials as well as for modelling climatic effects in the boreal and subarctic zones. Our goniometric measurements show that the reflectances of the most common land cover types in the boreal and subarctic region can differ from each other by a factor of 100. Some types are strong forward scatterers, some backward scatterers, some reflect specularly, some have strong colours, some are bright in visual, some in infrared. We noted that spatial variations in reflectance, even among the same type of vegetation, can be well over 20%, diurnal variations of the same order and seasonal variation often over a factor of 10. This has significant consequences on the interpretation of satellite and airborne images and on the development of radiation regime models in both optical remote sensing and climate change research. We propose that the accuracy of optical remote sensing can be improved by an order of magnitude, if better physical reflectance models can be introduced. Further improvements can be reached by more optimised design of sensors and orbits/flight lines, by the effective combining of several data sources and better processing of atmospheric effects. We conclude that more extensive and systematic laboratory experiments and field measurements are needed, with more modelling effort

Gold Coating of Respiratory Cilia for Scanning Electron Microscopy

The optimal thickness of gold coating of cilia for scanning electron microscopy was studied using respiratory mucosa obtained from pigs. We tested 8 different coating times, from 10 seconds to 4 minutes, which resulted in gold layer thicknesses varying from 16 ± 1 nm to 100 ± 3 nm. The thickness of the gold layer with a coating time of 60 seconds and voltage of 2.5 kV was 43 ± 5 nm. This thickness of gold layer gave good image quality without causing any electric charging. With thinner gold films, the amount of electric charging increased. When the coating time was longer, the gold layer was thicker but image quality did not improve. The thicknesses of the gold layers were measured using transmission electron microscopy (TEM)

Regional Eradication of Mycoplasma hyopneumoniae From Pig Herds and Documentation of Freedom of the Disease

The objectives of this study were to 1) screen all sow herds in a region for M. hyopneumoniae, 2) to effectuate an eradication programme in all those herds which were shown to be infected with M. hyopneumoniae, and 3) to follow the success of the screening and the eradication programmes. The ultimate goal was to eradicate M. hyopneumoniae from all member herds of a cooperative slaughterhouse (153 farrowing herds + 85 farrowing-to-finishing herds + 150 specialised finishing herds) before year 2000. During 1998 and 1999, a total of 5067 colostral whey and 755 serum samples (mean, 25 samples/herd) were collected from sow herds and analysed for antibodies to M. hyopneumoniae by ELISA. Antibodies were detected in 208 (3.6%) samples. Two farrowing herds (1.3%) and 20 farrowing-to-finishing herds (23.5%) were shown to be infected with M. hyopneumoniae. A programme to eradicate the infection from these herds was undertaken. During March 2000, a survey was made to prove the success of the screening and the eradication programmes. In total, 509 serum samples were collected randomly from slaughtered finishing pigs. Antibodies to M. hyopneumoniae were not detected in 506 of the samples, whereas 3 samples were considered suspicious or positive. Accordingly, 3 herds were shown to be infected. One of the herds was previously falsely classified as non-infected. Two of the herds were finishing herds practising continuous flow system (CF). Unlike finishing herds which practice all-in/all-out management routines on herd level, CF herds do not get rid of transmissible diseases spontaneously between batches, for which reason a screening was made in the rest of the CF herds (total n = 7). Consequently, 2 more infected herds were detected. In addition to the results of the survey, a decreasing prevalence of lung lesions at slaughter (from 5.2% to 0.1%) and lack of clinical breakdowns indicated that all member herds were finally free from M. hyopneumoniae in the end of year 2000

Radial Dependence of the Pattern Speed of M51

The grand-design spiral galaxy M51 has long been a crucial target for theories of spiral structure. Studies of this iconic spiral can address the question of whether strong spiral structure is transient (e.g. interaction-driven) or long-lasting. As a clue to the origin of the structure in M51, we investigate evidence for radial variation in the spiral pattern speed using the radial Tremaine-Weinberg (TWR) method. We implement the method on CO observations tracing the ISM-dominant molecular component. Results from the method's numerical implementation--combined with regularization, which smooths intrinsically noisy solutions--indicate two distinct patterns speeds inside 4 kpc at our derived major axis PA=170 deg., both ending at corotation and both significantly higher than the conventionally adopted global value. Inspection of the rotation curve suggests that the pattern speed interior to 2 kpc lacks an ILR, consistent with the leading structure seen in HST near-IR observations. We also find tentative evidence for a lower pattern speed between 4 and 5.3 kpc measured by extending the regularized zone. As with the original TW method, uncertainty in major axis position angle (PA) is the largest source of error in the calculation; in this study, where \delta PA=+/-5 deg. a ~20% error is introduced to the parameters of the speeds at PA=170 deg. Accessory to this standard uncertainty, solutions with PA=175 deg. (also admitted by the data) exhibit only one pattern speed inside 4 kpc, and we consider this circumstance under the semblance of a radially varying PA.Comment: 14 pages in emulateapj format, 12 figures, accepted for publication in Ap