New far-infrared and submillimeter photometry from the Herschel Space Observatory is presented for 61 nearby galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel ...(KINGFISH) sample. The spatially integrated fluxes are largely consistent with expectations based on Spitzer far-infrared photometry and extrapolations to longer wavelengths using popular dust emission models. Dwarf irregular galaxies are notable exceptions, as already noted by other authors, as their 500 mu m emission shows evidence for a submillimeter excess. In addition, the fraction of dust heating attributed to intense radiation fields associated with photodissociation regions is found to be (21 + or - 4)% larger when Herschel data are included in the analysis. Dust masses obtained from the dust emission models of Draine & Li are found to be on average nearly a factor of two higher than those based on single-temperature modified blackbodies, as single blackbody curves do not capture the full range of dust temperatures inherent to any galaxy. The discrepancy is largest for galaxies exhibiting the coolest far-infrared colors.
NGC 1097 is a nearby SBb galaxy with a Seyfert nucleus and a bright starburst ring. We study the physical properties of the interstellar medium (ISM) in the ring using spatially resolved far-infrared ...spectral maps of the circumnuclear starburst ring of NGC 1097, obtained with the PACS spectrometer on board the Herschel Space Observatory. In particular, we map the important ISM cooling and diagnostic emission lines of OI 63 μm, OIII 88 μm, NII 122 μm, CII 158 μm and NII 205 μm. We observe that in the OI 63 μm, OIII 88 μm, and NII 122 μm line maps, the emission is enhanced in clumps along the NE part of the ring. We observe evidence of rapid rotation in the circumnuclear ring, with a rotation velocity of ~220 km s-1 (inclination uncorrected) measured in all lines. The OI 63 μm/CII 158 μm ratio varies smoothly throughout the central region, and is enhanced on the northeastern part of the ring, which may indicate a stronger radiation field. This enhancement coincides with peaks in the OI 63 μm and OIII 88 μm maps. Variations of the NII 122 μm/NII 205 μm ratio correspond to a range in the ionized gas density between 150 and 400 cm-3.
We have mapped the key mid-IR diagnostics in eight major merger systems of the Toomre sequence (NGC 4676, NGC 7592, NGC 6621, NGC 2623, NGC 6240, NGC 520, NGC 3921, and NGC 7252) using the Spitzer ...Infrared Spectrograph. With these maps, we explore the variation of the ionized-gas, polycyclic aromatic hydrocarbon (PAH), and warm gas (H2) properties across the sequence and within the galaxies. While the global PAH interband strength and ionized gas flux ratios (Ne III/Ne II) are similar to those of normal star-forming galaxies, the distribution of the spatially resolved PAH and fine structure line flux ratios is significantly different from one system to the other. Rather than a constant H2/PAH flux ratio, we find that the relation between the H2 and PAH fluxes is characterized by a power law with a roughly constant exponent (0.61 ? 0.05) over all merger components and spatial scales. While following the same power law on local scales, three galaxies have a factor of 10 larger integrated (i.e., global) H2/PAH flux ratio than the rest of the sample, even larger than what it is in most nearby active galactic nuclei. These findings suggest a common dominant excitation mechanism for H2 emission over a large range of global H2/PAH flux ratios in major mergers. Early-merger systems show a different distribution between the cold (CO J = 1-0) and warm (H2) molecular gas components, which is likely due to the merger interaction. Strong evidence for buried star formation in the overlap region of the merging galaxies is found in two merger systems (NGC 6621 and NGC 7592) as seen in the PAH, Ne II, Ne III, and warm gas line emission, but with no apparent corresponding CO (J = 1-0) emission. The minimum of the 11.3/7.7 Delta *mm PAH interband strength ratio is typically located in the nuclei of galaxies, while the Ne III/Ne II ratio increases with distance from the nucleus. Our findings also demonstrate that the variations of the physical conditions within a merger are much larger than any systematic trends along the Toomre sequence.
[C II] 158 μm EMISSION AS A STAR FORMATION TRACER Herrera-Camus, R; Bolatto, A D; Wolfire, M G ...
Astrophysical journal/The Astrophysical journal,
02/2015, Letnik:
800, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The CII 157.74 mu m transition is the dominant coolant of the neutral interstellar gas, and has great potential as a star formation rate (SFR) tracer. Using the Herschel KINGFISH sample of 46 nearby ...galaxies, we investigate the relation of CII surface brightness and luminosity with SFR. We conclude that CII can be used for measurements of SFR on both global and kiloparsec scales in normal star-forming galaxies in the absence of strong active galactic nuclei (AGNs). The uncertainty of the capital sigma sub(CII) - capital sigma sub(SFR) calibration is + or -0.21 dex. The main source of scatter in the correlation is associated with regions that exhibit warm IR colors, and we provide an adjustment based on IR color that reduces the scatter. We show that the color-adjusted capital sigma sub(CII) - capital sigma sub(SFR) correlation is valid over almost five orders of magnitude in capital sigma sub(SFR), holding for both normal star-forming galaxies and non-AGN luminous infrared galaxies. Using CII luminosity instead of surface brightness to estimate SFR suffers from worse systematics, frequently underpredicting SFR in luminous infrared galaxies even after IR color adjustment (although this depends on the SFR measure employed). We suspect that surface brightness relations are better behaved than the luminosity relations because the former are more closely related to the local far-UV field strength, most likely the main parameter controlling the efficiency of the conversion of far-UV radiation into gas heating. A simple model based on Starburst99 population-synthesis code to connect SFR to CII finds that heating efficiencies are l%-3% in normal galaxies.
ABSTRACT
The N
ii
122 and 205
μ
m transitions are powerful tracers of the ionized gas in the interstellar medium. By combining data from 21 galaxies selected from the
Herschel
KINGFISH and Beyond ...the Peak surveys, we have compiled 141 spatially resolved regions with a typical size of ∼1 kpc, with observations of both N
ii
far-infrared lines. We measure N
ii
122/205 line ratios in the ∼0.6–6 range, which corresponds to electron gas densities of
n
e
∼ 1–300 cm
−3
, with a median value of
n
e
= 30 cm
−3
. Variations in the electron density within individual galaxies can be as high as a factor of ∼50, frequently with strong radial gradients. We find that
n
e
increases as a function of infrared color, dust-weighted mean starlight intensity, and star-formation rate (SFR) surface density (Σ
SFR
). As the intensity of the N
ii
transitions is related to the ionizing photon flux, we investigate their reliability as tracers of the SFR. We derive relations between the N
ii
emission and SFR in the low-density limit and in the case of a log-normal distribution of densities. The scatter in the correlation between N
ii
surface brightness and Σ
SFR
can be understood as a property of the
n
e
distribution. For regions with
n
e
close to or higher than the N
ii
line critical densities, the low-density limit N
ii
-based SFR calibration systematically underestimates the SFR because the N
ii
emission is collisionally quenched. Finally, we investigate the relation between N
ii
emission, SFR, and
n
e
by comparing our observations to predictions from the MAPPINGS-III code.
The physical state of interstellar gas and dust is dependent on the processes which heat and cool this medium. To probe heating and cooling of the interstellar medium over a large range of infrared ...surface brightness, on sub-kiloparsec scales, we employ line maps of CII 158 mu m, OI 63 mu m, and NII 122 mu m in NGC 1097 and NGC 4559, obtained with the Photodetector Array Camera & Spectrometer on board Herschel. We matched new observations to existing Spitzer Infrared Spectrograph data that trace the total emission of polycyclic aromatic hydrocarbons (PAHs). We confirm at small scales in these galaxies that the canonical measure of photoelectric heating efficiency, (CII + OI)/TIR, decreases as the far-infrared (far-IR) color, nufunctionof sub(nu)(70 mu m) nufunctionof sub(nu)(100 mu m), increases. In contrast, the ratio of far-IR cooling to total PAH emission, (CII + OI)/PAH, is a near constant ~6% over a wide range of far-IR color, 0.5 < nufunctionof sub(nu)(70 mu m) nufunctionof sub(nu)(100 mu m) <, ~0.95. In the warmest regions, where nufunctionof sub(nu)(70 mu m) nufunctionof sub(nu)(100 mu m) > ~0.95, the ratio (CII + OII)/PAH drops rapidly to 4%. We derived representative values of the local ultraviolet radiation density, G sub(0), and the gas density, n sub(H), by comparing our observations to models of photodissociation regions. The ratio G sub(0)/n sub(H), derived from fine-structure lines, is found to correlate with the mean dust-weighted starlight intensity, left angle bracketUright angle bracket, derived from models of the IR spectral energy distribution. Emission from regions that exhibit a line deficit is characterized by an intense radiation field, indicating that small grains are susceptible to ionization effects. We note that there is a shift in the 7.7/11.3 mu m PAH ratio in regions that exhibit a deficit in (CII + OI)/PAH, suggesting that small grains are ionized in these environments.
Breast cancer is the most common cancer among women and its metastatic potential is responsible for numerous deaths. Thus, the need to find new targets for improving treatment, and even finding the ...cure, becomes increasingly greater. Ion channels are known to participate in several physiological functions, such as muscle contraction, cell volume regulation, immune response and cell proliferation. In breast cancer, different types of ion channels have been associated with tumorigenesis. Recently, voltage-gated Na+ channels (VGSC) have been implicated in the processes that lead to increased tumor aggressiveness. To explain this relationship, different theories, associated with pH changes, gene expression and intracellular Ca2+, have been proposed in an attempt to better understand the role of these ion channels in breast cancer. However, these theories are having difficulty being accepted because most of the findings are contrary to the present scientific knowledge. Several studies have shown that VGSC are related to different types of cancer, making them a promising pharmacological target against this debilitating disease. Molecular biology and cell electrophysiology have been used to look for new forms of treatment aiming to reduce aggressiveness and the disease progress.
Biomedical signals constitute time-series that sustain machine learning techniques to achieve classification. These signals are complex with measurements of several features over, eventually, an ...extended period. Characterizing whether the data can anticipate prediction is an essential task in time-series mining. The ability to obtain information in advance by having early knowledge about a specific event may be of great utility in many areas. Early classification arises as an extension of the time-series classification problem, given the need to obtain a reliable prediction as soon as possible. In this work, we propose an information-theoretic method, named Multivariate Correlations for Early Classification (MCEC), to characterize the early classification opportunity of a time-series. Experimental validation is performed on synthetic and benchmark data, confirming the ability of the MCEC algorithm to perform a trade-off between accuracy and earliness in a wide-spectrum of time-series data, such as those collected from sensors, images, spectrographs, and electrocardiograms.
The metal content of a galaxy, a key property for distinguishing between viable galaxy evolutionary scenarios, strongly influences many of the physical processes in the interstellar medium. An ...absolute and robust determination of extragalactic metallicities is essential in constraining models of chemical enrichment and chemical evolution. Current gas-phase abundance determinations, however, from optical fine-structure lines are uncertain to 0.8 dex as conversion of these optical line fluxes to abundances is strongly dependent on the electron temperature of the ionized gas. In contrast, the far-infrared (far-IR) emission lines can be used to derive an O super(++) abundance that is relatively insensitive to temperature, while the ratio of the optical to far-IR lines provides a consistent temperature to be used in the derivation of an O super(+) abundance. We present observations of the OIII 88 mu m fine-structure line in NGC 628 that were obtained as part of the Key Insights on Nearby Galaxies: a Far Infared Survey with Herschel program. These data are combined with optical integrated field unit data to derive oxygen abundances for seven H II regions. We find the abundance of these regions to all lie between the high and low values of strong-line calibrations and to be in agreement with estimates that assume temperature fluctuations are present in the H II regions.
We present high spatial resolution (image35 pc) 5-38 mum spectra of the central region of M82, taken with the Spitzer Infrared Spectrograph. From these spectra we determined the fluxes and equivalent ...widths (EWs) of key diagnostic features, such as the Ne ii 12.8 mum, Ne iii 15.5 mum, and H sub(2) S(1) 17.03 mum lines, and the broad mid-IR polycyclic aromatic hydrocarbon (PAH) emission features in six representative regions and analyzed the spatial distribution of these lines and their ratios across the central region. We find a good correlation of the dust extinction with the CO 1-0 emission. The PAH emission follows closely the ionization structure along the galactic disk. The observed variations of the diagnostic PAH ratios across M82 can be explained by extinction effects, within systematic uncertainties. The 16-18 mum PAH complex is very prominent, and its EW is enhanced outward from the galactic plane. We interpret this as a consequence of the variation of the UV radiation field. The EWs of the 11.3 mum PAH feature and the H sub(2) S(1) line correlate closely, and we conclude that shocks in the outflow regions have no measurable influence on the H sub(2) emission. The Ne iii/Ne ii ratio is on average low, at image0.18, and shows little variations across the plane, indicating that the dominant stellar population is evolved (5-6 Myr) and well distributed. There is a slight increase of the ratio with distance from the galactic plane of M82, which we attribute to a decrease in gas density. Our observations indicate that the star formation rate has decreased significantly in the last 5 Myr. The quantities of dust and molecular gas in the central area of the galaxy argue against starvation and for negative feedback processes, observable through the strong extraplanar outflows.
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