Haut PDF Study of the Far Infrared Emission of Nearby Spiral Galaxies

Study of the Far Infrared Emission of Nearby Spiral Galaxies

Study of the Far Infrared Emission of Nearby Spiral Galaxies

Only then these clumps gravitationally attracted visible matter, as well as more dark matter. The currently observed distribution of specific angular momentum (angular momentum per unit mass) of disk galaxies suggest very specific formation scenarios (although uncertainties remain, see Dutton and van den Bosch, 2012). Namely, the infalling gas is traditionnally deemed to have been shock-heated (see Wang and Abel, 2008) to the dark halo virial temperature, even though some studies showed the important role played by “cold-mode” filamentary gaseous infalls for which shock-heating is less efficient (see Stewart et al., 2013, Dubois et al., 2012). In the shock-heating scenario the distribution of specific angular momentum assumed to be first acquired by baryons, after shock-heating is the same as that of the pre-existing dark matter halo. As brought forward by Dalcanton et al. (1997), Mestel et al. (1963) showed that the angular momentum distribution of a galactic disk is very similar to that of a sphere in solid body rotation. Thus it was then assumed that the collapse of a uniformly rotating gaseous protogalaxy was a good model for disk formation. As explained in Kaufmann et al. (2006), to obtain the observed exponential decrease of stellar density with radius, very little angular momentum transport is expected to have occured in the gas while it was collapsing inside dark halos. It is also expected that the angular momentum is responsible for eventually halting the collapse and that dark halos originally have a radial density profile such that the observed rotation velocity profile of disks are mainly flat at large distances from the center (see Dalcanton et al., 1997).
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LeMMINGs – I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

LeMMINGs – I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

broadly follow a similar correlation in the optical FPBHA, stretch- ing their luminosities up to FR I radio galaxies. Therefore, in the low-luminosity regime, the physical process which regulates the conversion of the accretion flow into radiative and kinetic jet en- ergy could be universal across the entire SMBH mass scale and for different optical classes. Such a process does not necessarily require the same disc–jet coupling since the classes are differently powered. Instead, it points to a common scaling relation in terms of BH properties (mass, spin, disc-BH alignment, and co-rotation), accretion, and jet production, which are distinct for each AGN class, but become similar when all are properly combined in the FPBHA, as validated by magnetic–hydrodynamic simulations (Heinz & Sunyaev 2003). However, we should point out that a slight sep- aration of the different optical classes is still evident across the optical FPBHA (with the Seyferts at lower radio luminosities than LINERs), which was not observed in previous works at lower VLA resolution. Resolving the parsec-scale jet base, thanks to eMERLIN, has helped to bring this effect in the Fundamental Plane to light. The origin of this stratification in the optical FPBHA might be still reminiscent of the different accretion modes for each optical class. The LeMMINGs project has uncovered new radio active SMBHs in the local Universe, which were not detected and identified be- fore. This discovery is fundamental for conducting a fair census of the local BH population and to provide robust constraints on cos- mological galaxy evolution models (Shankar 2009). The local BH demographics and the study of the BH activity are currently still limited to a few single-band observations, circumscribed to small samples. The LeMMINGs legacy survey will address these topics with a multiband approach applied to a complete sample, pushing the low end of the radio luminosity function. In fact, further eMER- LIN observations at C band (5 GHz) will, for the first time, extend the radio luminosity function of the local Universe down to 10 times the luminosity of Sgr A* and help to discriminate SF from genuine AGN activity. Furthermore, complementary data, which include optical (HST), X-ray (Chandra), and infrared (Spitzer) band, will unveil the origin of the parsec-scale radio emission and properties of the central engines of the local LLAGN population.
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Modelling the ultraviolet-to-infrared spectral energy distributions of galaxies

Modelling the ultraviolet-to-infrared spectral energy distributions of galaxies

3.3. Application to the SINGS sample 87 The total infrared luminosity L d tot and the stellar mass M ∗ remain reasonably well constrained. We note that, if a galaxy has mid-infrared colours characteristic of Galactic cirrus emission, and if no other spectral information is available at shorter and longer wavelengths to constrain f µ , it may be difficult to disentangle the contributions by stellar birth clouds and the ambient ISM to the total infrared luminosity. Galaxies with cirrus-like mid-infrared emission in the SINGS sample tend to have low specific star formation rates and infrared spectra dominated by the emission from ambient- ISM dust (as is the case, for example, for NGC 3521 in Fig. 3.4a). The inclusion of either far-infrared observations to constrain the temperature of the dust in thermal equilibrium or ultraviolet and optical observations to constrain the attenuation of starlight by dust can lift the ambiguity about the origin of the infrared emission (this is illustrated by the reasonably tight constraints obtained on f µ for NGC 3521 in all the cases considered in Fig. 3.5). We have checked that the predicted mid- infrared emission of the ambient ISM in these analyses is always consistent with the expectation that stellar ultraviolet photons (with λ < 3500 ˚ A) are the main contributors to the excitation of PAH molecules and the stochastic heating of dust grains responsible for the hot mid-infrared continuum. This is because stars slightly older than 10 7 yr, which have migrated from their birth clouds into the ambient ISM, are still bright in the ultraviolet. In the SINGS sample, for example, ultraviolet photons generated by stars older than 10 7 yr account for about 5 per cent of the heating of ambient-ISM dust for galaxies with the lowest specific star formation rates (ψ S ). This fraction reaches about 85 per cent for galaxies with the highest ψ S . At the same time, PAHs and the hot mid-infrared continuum are found to produce from about 1 per cent to about 35 per cent, respectively, of the infrared luminosity of the ambient ISM in these galaxies. Thus, enough stellar ultraviolet photons are produced to account for the mid-infrared emission from PAHs and hot dust in the ambient ISM of these galaxies, even if a large part are absorbed by cooler grains in thermal equilibrium.
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The far-infrared spectroscopic surveyor (FIRSS)

The far-infrared spectroscopic surveyor (FIRSS)

The ISM gas in our Galaxy and external galaxies can be found in atomic, ionized or molecular state, with a range of densities and temperatures. The ISM can be fur- ther characterized by a few ‘phases’ depending on physical conditions: ionized gas is found as coronal gas in the hot ionized medium (HIM, at T ∼ 10 6 K and n ∼ 0.04 cm −3 ) and as warm ionized medium (WIM, at T ∼ 10 4 K gas) in which most of the hydrogen is in H + , and includes diffuse intercloud gas (with n ∼0.3 cm −3 ) and denser HII regions (with n ∼ 10 4 cm −3 ) photoionized by nearby massive stars. In addition, two neutral atomic phases coexist at roughly thermal pressure equilibrium (e.g. [127]); the warm neutral medium (WNM, with T ∼ 10 4 K and n ∼0.3 cm −3 ) and the cold neutral medium (CNM, T ∼80 K and n∼40 cm −3 ). In the densest gas regions, hydrogen turns molecular, forming giant molecular clouds that are prime sites for star formation. However, in recent years, it has become apparent that the tra- ditional distinction of the ISM into these well-separated, thermally and chemically stable phases does not reflect the dynamic nature of the ISM evolution. A large frac- tion of the gas can be found in transitional regions. To obtain a full inventory of the interstellar gas, observations of all phases and the transitions between them are needed. Local and global thermal pressure variations regulate the amount of material in the different phases. Pressure disturbances from shocks of expanding shells and spiral density waves can redistribute material from the WNM regime to the CNM component, where it is generally assumed that molecular gas develops. The pres- sure modulates the CNM/ WNM ratio and in turn, the molecular gas fraction [24]. Together with the tight correlation between molecular gas and the star-formation rate on galaxy scales this suggests that the gas pressure is a dominant parameter for star- formation. However, [55] have shown that these relations break down on the scale of giant molecular clouds and the observations in the central region of the Milky Way reveals low star-formation activity at high pressure [53]. To understand galactic star formation and the evolution of our Galaxy we need to measure the pressure and decompose it into thermal, turbulent, and magnetic components. This requires imag- ing of spectral line emission from well-defined tracers of the ionized, neutral atomic, and molecular gas phases of the ISM. The spectral maps measure the distribution of gas and establish spatial and kinematic relationships between different phases.
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Unveiling Far-Infrared Counterparts of Bright Submillimeter Galaxies Using PACS Imaging

Unveiling Far-Infrared Counterparts of Bright Submillimeter Galaxies Using PACS Imaging

100 µm (160 µm) of 6.7 ′′ (11.0 ′′ ) provide a more accurate location of the dust emission than the bolometer data taken with SCUBA, AzTEC, MAMBO or LABOCA. In this letter we discuss our search for PACS counter- parts at 100 µm and 160 µm, explore the diagnostic potential of Herschel-PACS for the counterpart identifi- cation and compare it with the widely used identification approach using VLA observations. In comparison, the Spitzer-MIPS 70 µm and 160 µm imaging of the GOODS North region performed by Huynh et al. (2007) in the pre-Herschel era detected at relatively high significance only two (one) out of 30 SMGs at 70 µm (160 µm), at rather low redshifts (z = 0.5 and z = 1.2). The FIR observations presented here will enable us to study a significant sample of SMGs in the far-infrared wavelength regime.
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The [CII] 158 μm line emission in high-redshift galaxies

The [CII] 158 μm line emission in high-redshift galaxies

is surely present even if in small amounts (Riechers et al. 2013; Watson et al. 2015) and can strongly a ffect SFR measurements based on UV-luminosity. With the advent of the Atacama Large Millimeter Array (ALMA) and NOEMA, it is now possible to measure the dust content of very high redshift galaxies, but also to use far-infrared fine-structure lines (as [OIII] or [CII]) to study the physical con- ditions of their interstellar medium (ISM). The [OIII] line, orig- inating from di ffuse and highly ionized regions near young O stars, is a promising line (Inoue et al. 2016) that might gain in importance in low-metallicity environments where photo- dominated regions (PDRs) may occupy only a limited volume of the ISM. The [CII] line, predominantly originating from PDRs at high redshift (Stacey et al. 2010; Gullberg et al. 2015), can provide SFR estimates that are not biased by dust extinction, al- though it has been found to depend strongly on the metallicity (Vallini et al. 2015; Olsen et al. 2017). This line can also be used to measure the systemic redshift of the galaxies (e.g., Pentericci et al. 2016). In addition, the [CII]-line ALMA surveys will derive the line luminosity functions, thus measuring the abundance and intensity distributions of [CII] emitters (Aravena et al. 2016).
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Dust emission from clusters of galaxies: statistical detection

Dust emission from clusters of galaxies: statistical detection

Fig. 3. Stacked map (31.5  × 31.5  ) at 100 µm after 10 a), 50 b), 200 c), 1000 d), 4000 e), and 11507 f) cluster maps summed. The intensity is scaled between −50 000 to 50 000 Jy/sr for all the maps. in Sect. 2.1, has been overplotted with a dotted line. It first appears that the galaxy clusters are resolved. Neverthless the inaccuracy in the position of the cluster center implies an ar- tificial extension of the profiles. This has been tested in Fig. 6 by plotting the profiles at 100 µm obtained for a catalogue of distant clusters (LCDSC dealing with z ≥ 0.3, Gonzales et al. 2001) and for a catalogue of nearby clusters (WBL dealing with 0.01 ≤ z ≤ 0.03, White et al. 1999). The two profiles for nearby (solid line) and distant (dashed line) clusters are very similar (see Fig. 6). Moreover a new PSF, expressed as the product of the resolution given by IRIS and an inaccuracy of 2  in the position of the cluster, has been overplotted (dot- ted line), and matches very well the profiles obtained. The fact that the far and nearby clusters have the same extension im- plies that this extension is an artifact due to the inaccuracy in the position of cluster. The galaxy clusters are not resolved by this method. Moreover this average emission from galaxy clus- ters is only a low estimate, because of the dilution in the IRAS beam of the smaller clusters, and the subtraction of the mean level of emission for the very nearby clusters extending beyond the 30 × 30 arcmin field of view.
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Thick discs, and an outflow, of dense gas in the nuclei of nearby Seyfert galaxies

Thick discs, and an outflow, of dense gas in the nuclei of nearby Seyfert galaxies

Based on a variety of sources and methods, Hicks et al. ( 2009 ) ar- gued that the typical gas mass fraction lies in the range 4–25 per cent, with a typical value of f gas ∼ 0.1, within the central 200 pc of Seyferts. We adopt this value and, based on equation (7), draw in Fig. 10 the lines corresponding to α HCN = 3 (long dashed line), 10 (dot–dashed line), and 25 (dotted line). We find that α HCN = 10 M (K km s −1 pc 2 ) −1 provides a remarkably good approximation to the data. A similar HCN conversion factor α HCN = 10 +10 −3 for nearby AGN (albeit with beam sizes ranging from a few arcsec up to 20 arcsec) was found via LVG analysis by Krips et al. ( 2008 ). As they noted, it is ∼2 times smaller than the α HCN = 25 estimated by Gao & Solomon ( 2004 ) for nearby spiral, infrared-luminous, and ultraluminous galaxies. However, Fig. 10 rules out such a high conversion factor for the centres of AGN since it would imply a gas fraction exceeding 50 per cent. The difference may point to- wards differing excitation conditions and molecular abundances in the environments, and there is plentiful theoretical and observa- tional evidence that X-ray excitation of gas by the AGN does have a major impact on both of these leading to an increase in the HCN luminosity (Lepp & Dalgarno 1996 ; Maloney et al. 1996 ; Kohno et al. 2003 ; Usero et al. 2004 ; Boger & Sternberg 2005 ; Meijerink & Spaans 2005 ; Krips et al. 2007 ; Meijerink et al. 2007 ; Krips et al.
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Dust spectral energy distributions of nearby galaxies: an insight from the Herschel Reference Survey

Dust spectral energy distributions of nearby galaxies: an insight from the Herschel Reference Survey

We gather infrared photometric data from 8 µm to 500 µm from Spitzer, WISE, IRAS, and Herschel for all of the HRS galaxies. Draine & Li (2007, ApJ, 663, 866) models are fit to the data from which the stellar contribution has been carefully removed. We find that our photometric coverage is sufficient to constrain all of the parameters of the Draine & Li models and that a strong constraint on the 20−60 µm range is mandatory to estimate the relative contribution of the photo-dissociation regions to the infrared spectral energy distribution (SED). The SED models tend to systematically underestimate the observed 500 µm flux densities, especially for low-mass systems. We provide the output parameters for all of the galaxies, i.e., the minimum intensity of the interstellar radiation field, the fraction of polycyclic aromatic hydrocarbon (PAH), the relative contribution of PDR and evolved stellar population to the dust heating, the dust mass, and the infrared luminosity. For a subsample of gas-rich galaxies, we analyze the relations between these parameters and the main integrated properties of galaxies, such as stellar mass, star formation rate, infrared luminosity, metallicity, Hα and H-band surface brightness, and the far-ultraviolet attenuation. A good correlation between the fraction of PAH and the metallicity is found, implying a weakening of the PAH emission in galaxies with low metallicities and, thus, low stellar masses. The intensity of the diffuse interstellar radiation field and the H-band and Hα surface brightnesses are correlated, suggesting that the diffuse dust component is heated by both the young stars in star-forming regions and the di ffuse evolved population.
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A resolved analysis of cold dust and gas in the nearby edge-on spiral NGC 891

A resolved analysis of cold dust and gas in the nearby edge-on spiral NGC 891

In order to better understand whether the asymmetry arises due to higher rates of star formation in the north or greater dust obscuration in the south, it is crucial to study the dust surface density and temperature distributions. Firstly, we noted that in the extended disc, beyond the radial extent of the “molecular ring” (i.e. R > 6 kpc), the dust surface density distribution is fairly symmetric between the NE and SW ends of the disc, i.e., both sides contain similar quantities of dust grains available to obscure star-forming regions. Thus, it is unlikely that there is an increase in dust obscuration due to a mere enhancement of the dust distribution in the SW end. However, we cannot completely rule out the scenario due to the presence of a small asymmetry in the distribution. The temperature of the dust in the NE end of the disc is on average warmer (by ∼2−3 K) than the dust at corresponding radii on the SW end of the disc (see the dust temperature profile in Fig. 3 ). This warmer region in the NE is coincident with the peaks in the emission of the Hα and UV images ( Kamphuis et al. 2007 ), and also the peak in the ratio map of 24 μm to 850 μm emission (see Fig. 7 in Whaley et al. 2009 ; see also our Fig. 13 ). The latter ratio traces the relative contribution of warm dust associated with star formation and the emission from cold dust. Furthermore, we find that the ISM emission as traced by the WISE F 12 /F 22 flux ratio, i.e. the ratio of the emission from polycyclic aromatic hydrocarbons (PAHs) and dust warmed via the UV radiation field and the old stellar population, is also asymmetric (see the black contours in Fig. 12 ). The contours tracing the ISM are clearly more radially extended on the NE side than the SW side of the disc, and show some overlap with the peak in the cold dust temperature map.
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Toward the Comprehension of the Infrared to Submillimeter View of the Interstellar Medium of Nearby Galaxies

Toward the Comprehension of the Infrared to Submillimeter View of the Interstellar Medium of Nearby Galaxies

1.2.3 The ionised gas Hot ionised gas This phase is also called coronal gas or hot intercloud medium (HIM). The HIM shows very hot temperatures varying between 10 5 and 10 6 K and is very tenuous, with a density of ∼ 3 × 10 −3 cm −3 (Table 1.2 ). It fills most of the volume of the halo and is mainly heated and ionised by stellar winds of dying stars or by shock waves created by supernova explosions. Since coronal gas is thought to be made of supernova ejecta material, its study will give us information on the metal- enrichment history of galaxies. Several radiation processes are taking place in this hot plasma: bremsstrahlung continuum emission (transition of a free electron between two states), discrete line emission (transition between two levels of the ion), radiative recombination continuum (capture of an electron into a bound state), dielectronic recombination lines (capture of a free electron into a doubly excited ion state) or two-photon continuum mission (simultaneous emission of two photons) (see the review by Ehle 2005). The HIM, in cooling supernova remnants, is a significant source of X-ray thermal emission and UV absorption lines. Hurwitz & Bowyer (1996 ) studied Ovi data and derived an exponential scale height of ∼ 600 pc whereas Savage et al. (2000 ) explored Ovi toward active galactic nuclei with FUSE (Far Ultraviolet Spectroscopic Explorer FUSE) and found a scale height of 2.7 ± 0.4 kpc. A following study on more than 100 early-type stars has been carried out by Bowen et al. (2008). Ferriere (1998) found that the hot gas seems to occupy a rather small fraction of the interstellar volume. This fraction is < 20% at low altitude and falls off gradually. The volume filling factor of this hot gas is, however, still highly debated.
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Analysis of dust emission in nearby galaxies : implications of the modeling assumptions

Analysis of dust emission in nearby galaxies : implications of the modeling assumptions

More recent space observatories have had an incredible impact on modern astrophysics, and this thesis is mainly based on measurements from these telescopes. The level of precision in IR observations was largely increased with the Spitzer Space Telescope ( Werner et al. 2004 ) launched in 2003, whose main mission ended in 2009 (the “warm” mission is still ongoing at the two shortest wavelengths). It was not a full-sky survey, but pointed observations, as was ISO. Spitzer carried 3 instruments to orbit. Among these, two are for photometry, IRAC (Infrared Array Camera; Fazio et al. 2004 ) and MIPS (Multiband Imaging Photometer for Spitzer; Rieke et al. 2004 ). IRAC photometric bands are centered on 3.6, 4.5, 5.8, and 8.0 µm, and MIPS bands on 24, 70, and 160 µm. The spectrometer, IRS (Infrared Spectrograph; Houck et al. 2004 ), covered 5 to 38 µm, with both high and low resolutions. The science questions that Spitzer was built to tackle were, among others, star formation or young stellar objects as well as dust, given its spectral coverage. Some programs used Spitzer, making significant contributions in dust analysis in nearby galaxies. The SINGS consortium ( Kennicutt et al. 2003 ) took measurements of 75 galaxies and focused on their IR emission and star formation properties. Two programs were meant to study in detail regions of the Small Magellanic Cloud (SMC), a nearby dwarf galaxy, in photometry and spectroscopy (S 3 MC, S 4 MC; Bolatto et al. 2007 ; Sandstrom et al. 2012 ). The SAGE surveys (SMC and LMC; Meixner et al. 2006 ; Gordon et al. 2011 ) were keys projects of the Spitzer program and are used in numerous studies.
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Study of $^{19} $Na at SPIRAL

Study of $^{19} $Na at SPIRAL

Na = 18 Ne + p), the probability for elastic scattering changes signifi- cantly. The scattered proton can escape the target because of its smaller energy loss, and can be detected at forward angles in the laboratory frame after escaping the target. There is a direct correspondence between the energy of the detected proton and the center of mass energy of the scattering event. In our experiment the target was thick enough to stop the beam inside the target. Therefore, the thick target makes it possible to obtain a complete and continuous excitation function over a wide range of ener- gies, by simply detecting the scattered protons and mea- suring their energies, without changing the energy of the incident beam. As measured for example by Axelsson et al. [8] with a thick target, the final resolution can be better than 50 keV in the center of mass frame, generally good enough to study states with large widths. The disadvan- tages to use a thick target are discussed hereafter.
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Study of the behavior of iron ore particles in spiral concentrators

Study of the behavior of iron ore particles in spiral concentrators

with the 3-turn-spiral. The departure from the anticipated recovery increase is systematic and cannot be attributed solely to the problems of the feed and wash water distribution systems, as discussed in sections 5-2- 2 and 5-2-3. A deterministic explanation in required to investigate this departure from the anticipated effect of the number of turns on spirals performance. So far, only Atasoy and Spottiswood (1995) have unsuccessfully attempted to identify the effect of the number of turns on spirals performance. We have to admit that we were unsuccessful too. Could the answer be that we are not looking adequately at the system? Indeed, increasing the number of turns offers more freedom to adjust the cutter openings and the wash water addition to the spiral trough. Obviously a 7-turn-spiral should outperform a 3 or a 5-turn-spiral as there are more adjustable variables to maximize the concentrate grade and/or the recovery. Therefore, instead of trying to find out the true effect of the number of turns on spirals performance maybe we should try to understand how the cutter positions and wash water should be adjusted to get the most out of a spiral. However, such quest is rather complex, as even a 3-turn-spiral uses 4 concentrate cutters with the openings that can be adjusted from 0 to 100%. The 3-turn-spiral has 9 wash water addition entries that can be adjusted through the spigot openings. Therefore, the optimization of even a 3-turn-spiral may require a huge experimental effort. The use of a mathematical model for the spiral may help in such investigation but such model for a spiral is still awaited for.
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A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic

A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic

± 1 K. Red error bars correspond to simulations with specific hu- midity profiles offset by ±10 %. measurements coincide so well in all bands suggests that the atmospheric reanalysis, the model and measurements are all consistent and of good quality. This provides a successful ra- diative closure experiment for clear-sky conditions (e.g., De- lamere et al., 2010; Fox et al., 2015). The high sensitivity of the simulations to specific humidity in F-IR bands (except 30–50 µm that is saturated) shows that the humidity profile must be precise with more than 5 % accuracy. It also points out that the FIRR resolution is sufficient to discriminate be- tween humidity profiles that differ by a few percent in a very dry atmosphere. The simulations nevertheless show an ap- parent negative bias in the F-IR, which is likely to be due to an erroneous water vapor profile. On the contrary, the results of the T-IR bands between 10 and 14 µm, which are sensitive to the whole atmospheric profile, ensure that the temperature profile is correct. The very low radiance measured in the 10– 12 µm band, which corresponds to a brightness temperature of −125 ◦ C, matches the simulation very well. It proves the quality of the calibration procedure, even when radiance is extrapolated far below the calibration BBs’ radiances. As for the observed bias in the 7.9–9.5 µm band, it can hardly be explained by errors on the water vapor or temperature pro- files. Based on a series of tests, it is rather likely the result of erroneous profiles of aerosols which were chosen some- how arbitrarily. Overall, these results are very encouraging for further investigation of the water cycle in the Arctic. 4.2.2 Winter cloudy-sky experiment
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Towards an Algorithmic Guide to Spiral Galaxies

Towards an Algorithmic Guide to Spiral Galaxies

If y is noninteger, then color (⌈y⌉, ⌈x⌉) red. Then check whether there is an uncolored field that belongs to the galaxy and is to the left or to the right of a red field. If this is the case, color it also red. When there is no such field, then note that the row of red fields is a separator of the galaxy. Color the g-twins of this line of red fields (which is the line below) blue. Now color all uncolored fields that can reach blue fields only via red fields with red and all other fields blue. The resulting coloring clearly fulfills the first and the last condition of the lemma. It remains to show the number of corners. At most ℓ/2 corners of the red area are also corners in g. In addition, there are at most two corners between red and blue fields (recall that the separator is a straight line of fields). Since g has at least four corners, the number of corners in the red fields is at most ℓ/2 + 2 ≤ ℓ. If y is integer, then color the field that contains y black. If the galaxy contains no further fields, then the lemma holds. Otherwise, distinguish two further cases.
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Added value of far-infrared radiometry for remote sensing of ice clouds

Added value of far-infrared radiometry for remote sensing of ice clouds

Yi et al. [2016]. 5. Conclusion This paper investigated the potential of FIR radiometry for the characterization of ice cloud properties, with a special focus on cloud effective particle diameter. To this end we used the optimal estimation framework, which provides the best estimate of cloud properties and the associated uncertainties given an a priori and a set of radiance observations. It was shown that in the polar regions and the upper tropical troposphere, FIR radiances contain much more information about cloud effective particle diameter than MIR radiances. This results from the advantageous spectral shift of Planck emission function in cold conditions and from the strong sensitivity of cloud particle single-scattering properties to effective diameter in the FIR. Using FIR observations could thus overcome the limitations of common MIR-based algorithms, increasing retrievals accuracy by more than 50% in most cases, and by nearly 100% in some conditions. This would extend the range of validity of existing algorithms to larger optical thickness, larger effective diameter, and to the polar regions in absence of sunlight, thus offering the possibility to observe the initiation of precipitation. Such advancements are promising for studying the microphysics of convective towers and poorly known polar thin ice clouds, which are known to be sensitive to anthropogenic influence through ice nucleation processes. Practically, the performance of existing FIR sensors are such that a radiometer with 2 or 3 FIR channels would be sufficient to significantly complement MIR observations. Increasing sensor radiometric resolution could provide another twofold in precision, and optimizing the channels spectral characteristics appears as another venue to improve retrieval performance. Future work should focus on the assessment of FIR-based retrievals, exploring a larger range of cloud cases. This could be done by coupling a FIR radiometer simulator to outputs of reanalysis or regional climate simulations. In summary, this work highlights the relevance of adding FIR observations to the existing Earth-observing system. Such FIR satellite is technologically feasible and highly recommended. In addition, it could be performed at a reasonable cost compared to projects involving high spectral resolution instruments.
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Towards an Algorithmic Guide to Spiral Galaxies

Towards an Algorithmic Guide to Spiral Galaxies

Proposition 1. One can determine in poly(k log n) time whether an instance of Spiral Galaxies has a solution that contains only size-1 and size-2 galaxies. Proof. Any size-1 or size-2 galaxy of center g is exactly its kernel κ(g). Thus any galaxy is completely determined by the location of its center. If we assume the input is correct (that is, no two kernels overlap), then we just need to check whether a field not belonging to a kernel exists in U . If this is the case, we have a no-instance. Otherwise, we have a yes-instance. The time complexity is in poly(n). Since we can reject any instance such that k < n 2 , we have k = Θ(n). Thus, poly(n) is polynomial in the input size.  The next three results, Theorems 2 to 4, are polynomial-time algorithms for restricted cases in which the shapes of the galaxies in a solution are constrained. These three results rely on the same generic idea. We iteratively fill the universe with galaxies. A field that is not yet assigned to any galaxy is called free in this process. Because of the shape constraint, it is always possible to find a free field f for which we can determine the unique galaxy center g it belongs to, together with the exact extent of the galaxy. If this process stops because no free field remains, it suffices to check whether the computed galaxies are pairwise nonoverlapping. Otherwise, at least one free field could not be assigned to any galaxy, and thus we are in presence of a no-instance.
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Spiral Arms in the Disk of HD 142527 from CO Emission Lines with ALMA

Spiral Arms in the Disk of HD 142527 from CO Emission Lines with ALMA

(A color version of this figure is available in the online journal.) Equation (1) after θ c instead of the minus sign given in Muto et al. (2012) since the disk of HD 142527 is rotating clockwise. First fits with Equation (1) were computed by fixing the values of α to 1.5 (Keplerian rotation) and β to 0.25 (see q in Section 2.3.1). We found plausible values of h c (between 0.01 and 1.0) with the points of the CO 2–1 I peak map for S1 (h c = 0.15) and S3 (h c = 0.27), but not for S2, and for neither spiral with the points of the CO 3–2 I peak map. In order to further reduce the parameter space, a second set of fits was run fixing as well the value of h c to 0.15. The best fit models are shown in solid dark gray lines in Figures 3(b) and (d); the inflection point in the spiral curves represents the best fit location of the planet. The values of the best fit r c , θ c , and χ 2 are given in Table 1.
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ORIGIN: Blind detection of faint emission line galaxies in MUSE datacubes

ORIGIN: Blind detection of faint emission line galaxies in MUSE datacubes

These spectra are collected in continuum and residual data cubes named b C and R respectively. The parameter N DCT controls the number of DCT basis vectors used in the continuum estimation. A value that is too small lets large scale oscillations in the resid- ual spectrum, while a value that is too large tends to capture spectral features with small extension like emission lines, which become then more difficult to detect in the residual. A satisfac- tory compromise was found here 1 with N DCT = 10. This value leaves the lines almost intact: typically, the energy of the line in the DCT residual remains close to 100% until N DCT reaches several hundreds, depending on the line width. The continuum subtraction with N DCT = 10 is not perfect, but a large part of the work is done: for bright objects, 99 % of the continuum’s energy is typically contained in the subspace spanned by the first 10 DCT modes and decreases very slightly afterward. The PCA does the rest.
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