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Mapping of molecular gas inflow towards the Seyfert nucleus of NGC 4051 using Gemini NIFS

Riffel, Rogemar André; Storchi-Bergmann, Thaisa; Winge, Claudia; McGregor, Peter J.; Beck, Tracy; Schmitt, Henrique Roberto
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
25.8%
We present 2D stellar and gaseous kinematics of the inner ~ 130×180 pc² of the Narrow-Line Seyfert 1 galaxy NGC4051 at a sampling of 4.5 pc, from near-infrared K-band spectroscopic observations obtained with the Gemini’s Near-infrared Integral Field Spectrograph (NIFS) operating with the ALTAIR adaptive optics module. We have used the CO absorption band heads around 2.3 μm to obtain the stellar kinematics which show the turnover of the rotation curve at only ≈ 55 pc from the nucleus, revealing a highly concentrated gravitational potential. The stellar velocity dispersion of the bulge is ≈ 60 km s-ˡ – implying on a nuclear black hole mass of ≈ 10 6 Mʘ – within which patches of lower velocity dispersion suggest the presence of regions of more recent star formation. From measurements of the emission-line profiles we have constructed 2D maps for the flux distributions, line ratios, radial velocities and gas velocity dispersions for the H2, HII and [Ca VIII] emitting gas. Each emission-line samples a distinct kinematics. The Brγ emission-line shows no rotation as well as no blueshifts or redshifts in excess of 30 km s-ˡ, and is thus not restricted to the galaxy plane. The [Ca VIII] coronal region is compact but resolved...

Quality control on radiant heaters manufacture

González Fernández, Daniel Aquilino; Madruga Saavedra, Francisco Javier; Ibarra Castanedo, Clemente; Conde Portilla, Olga María; López Higuera, José Miguel
Fonte: SPIE Society of Photo-Optical Instrumentation Engineers Publicador: SPIE Society of Photo-Optical Instrumentation Engineers
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
ENG
Relevância na Pesquisa
45.87%
An inspection process of radiant heaters is presented in this paper. The proposed non destructive testing and evaluation (NDT and E) technique for defect assessment of radiant heaters is based on infrared thermography images properly acquired and processed. The technique can be used in on-line fabrication quality control radiant heaters manufacturing processes. By exciting the heater with a very short electrical pulse, a sequence of thermographic images is captured by an infrared camera and then analyzed. Regardless of the electrical excitation applied to the heating element of the heater, the electrical power supplied will dissipate at the resistor. Provided enough spatial resolution, the heaters could be tested with an infrared camera capturing the radiated heat. The analysis of the heating wire during the heating flank shows differences among pixels corresponding to defective points and pixels belonging to non-defective areas of the wire. The automation is provided by the development of an algorithm that looks for the slope of the heating evolution of each pixel. A Radon Transform based algorithm is here proposed to reduce human intervention providing just one image where an operator could quickly locate possible defects.

Rational production of veneer by IR-heating of green wood during peeling: Modeling experiments

DUPLEIX, Anna; OULD AHMEDOU, Sid' Ahmed; BLÉRON, Laurent; ROSSI, Fréderic; HUGHES, Mark
Fonte: De Gruyter Publicador: De Gruyter
EN
Relevância na Pesquisa
45.86%
Heating green wood logs by infrared (IR) radiation during peeling for veneer production has been numerically simulated, focusing on the heating kinetics of a green wood cylinder rotating with a decreasing radius. The results confi rm those of previous experiments, that this kind of heating is a promising alternative to soaking wood prior to peeling. The model integrates the green wood parameters such as moisture content, density, distribution and ratios of earlywood and latewood, on the one hand, and the peeling conditions of veneer thickness and peeling speed, on the other. The following heat transfer processes were considered: conduction within the bolt, external heating by the IR source, and convection between the bolt surface and the external environment. The outputs were the temperatures of the bolt surface and of layers several millimeters deep. For maximal heat penetration, the bolt should turn in front of the IR source before cutting starts and the IR source should be positioned at the greatest angular distance ahead of the knife. Several heating scenarios could be simulated by the model, thus it is a useful decision-making tool for the design of an in-line IR heating system installed on the peeling lathe.; Institut Carnot ARTS...

Experimental validation of green wood peeling assisted by IR heating – some analytical system design considerations

DUPLEIX, anna; BATSALE, Jean-Christophe; KUSIAK, Andrzej; HUGHES, Mark; DENAUD, Louis
Fonte: de gruyter Publicador: de gruyter
EN
Relevância na Pesquisa
65.76%
Experimental results have been used to validate a 2D simulation model in order to check its reliability in predicting the heating of a green log rotating under an IR heating source. For the purpose of validation, it was assumed that this experimental situation could be described by simplified analytical solutions. This assumption has been confirmed. Knowing the thermal and physical characteristics of green wood, two methods are now available to calculate rapidly the temperature within the wood and the maximum surface temperature reached by a green log rotating under an IR heating source: (1) by numerical simulation and (2) by analytical equations which dispense with the computationally intensive finite element method. Experimental results, validated by both methods, show that an IR heating system embedded on an industrial peeling machine would not warm-up green wood to the required peeling temperature at current peeling speeds.; The research was carried out with the use of equipment funded by the French National Agency for Research under the program "Investments for the Future" (ANR-10-EQPX-16

On-line monitoring of methane in sewer air

Liu, Yiwen; Sharma, Keshab R.; Murthy, Sudhir; Johnson, Ian; Evans, Ted; Yuan, Zhiguo
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 16/10/2014 EN
Relevância na Pesquisa
45.67%
Methane is a highly potent greenhouse gas and contributes significantly to climate change. Recent studies have shown significant methane production in sewers. The studies conducted so far have relied on manual sampling followed by off-line laboratory-based chromatography analysis. These methods are labor-intensive when measuring methane emissions from a large number of sewers, and do not capture the dynamic variations in methane production. In this study, we investigated the suitability of infrared spectroscopy-based on-line methane sensors for measuring methane in humid and condensing sewer air. Two such sensors were comprehensively tested in the laboratory. Both sensors displayed high linearity (R2 > 0.999), with a detection limit of 0.023% and 0.110% by volume, respectively. Both sensors were robust against ambient temperature variations in the range of 5 to 35°C. While one sensor was robust against humidity variations, the other was found to be significantly affected by humidity. However, the problem was solved by equipping the sensor with a heating unit to increase the sensor surface temperature to 35°C. Field studies at three sites confirmed the performance and accuracy of the sensors when applied to actual sewer conditions...

ISO measurements of [CII] line variations in galaxies

Malhotra, S.; Helou, G.; Stacey, G.; Hollenbach, D.; Lord, S.; Beichman, C. A.; Dinerstein, H.; Hunter, D. A.; Lo, K. Y.; Lu, N. Y.; Rubin, R. H.; Silbermann, N.; Thronson Jr., H. A.; Werner, M. W.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/10/1997
Relevância na Pesquisa
35.89%
We report measurements of the [CII] fine structure line at 157.714 micron in 30 normal star-forming galaxies with the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). The ratio of the line to total far-infrared luminosity, [CII]/FIR, measures the ratio of the cooling of gas to that of dust; and thus the efficiency of the grain photoelectric heating process. This ratio varies by a factor of 40 in the current sample. About two-thirds of the galaxies have [CII]/FIR = 2-7 x 10^{-3}. The other one-third show trends of decreasing [CII]/FIR with increasing dust temperature, indicated by the ratio of infrared emission at 60 and 100 microns; and with increasing star-formation activity, measured by the ratio of far-infrared and blue band luminosity. We find three FIR bright galaxies with undetected [CII] line at 3-sigma upper limits of [CII]/FIR < 0.5-2 x 10^{-4}. The trend in the [CII]/FIR ratio with the temperature of dust and with star-formation activity may be due to decreased efficiency of photoelectric heating of gas at high UV radiation intensity as dust grains become positively charged, decreasing the yield and the energy of the photoelectrons. The three galaxies with no observed PDR lines have among the highest ratios of FIR to Blue luminosity and the ratio of 60 and 100 micron emission. Their lack of [CII] lines may be due to a continuing trend of decreasing [CII]/FIR with increasing star-formation activity and dust temperature seen in one-third of the sample with warm IRAS colors. In that case the upper limits on [CII]/FIR imply a ratio of UV flux to gas density G_0/n > 10 cm$^3. The low [CII]/FIR could also be due to either weak [CII] because of self-absorption or strong FIR continuum from regions weak in [CII]...

The origin of the infrared emission in radio galaxies. III. Analysis of 3CRR objects

Dicken, D.; Tadhunter, C.; Axon, D.; Robinson, A.; Morganti, R.; Kharb, P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/08/2010
Relevância na Pesquisa
25.84%
We present Spitzer photometric data for a complete sample of 19 low redshift (z<0.1) 3CRR radio galaxies as part of our efforts to understand the origin of the prodigious mid- to far-infrared (MFIR) emission from radio-loud AGN. Our results show a correlation between AGN power (indicated by [OIII] 5007 emission line luminosity) and 24 micron luminosity. This result is consistent with the 24 micron thermal emission originating from warm dust heated directly by AGN illumination. Applying the same correlation test for 70 micron luminosity against [OIII] luminosity we find this relation to suffer from increased scatter compared to that of 24 micron. In line with our results for the higher-radio-frequency-selected 2Jy sample, we are able to show that much of this increased scatter is due to heating by starbursts which boost the far-infrared emission at 70 micron in a minority of objects (17-35%). Overall this study supports previous work indicating AGN illumination as the dominant heating mechanism for MFIR emitting dust in the majority of low to intermediate redshift radio galaxies (0.03

Near/Mid Infrared-Wavelength Study of the Interacting Galaxy Pair UGC 12914/5 -- "Taffy"

Jarrett, T. H.; Helou, G.; Van Buren, D.; Valjavec, E.; Condon, J. J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/04/2000
Relevância na Pesquisa
35.83%
We report on an infrared 1 to 17 micron study of the nearby (cz = 4600 km/s) interacting spiral galaxy system, UGC 12914/12915, using the ground-based Palomar 200" telescope and PFIRCAM near-infrared detector and space-based mid-infrared imaging and spectral observations using ISOCAM and Phot-S on the Infrared Space Observatory (ISO). Strong line emission from aromatic band features at 6.2, 7.7 and 11.3 microns are seen in both the mid-IR imaging and Phot-S spectro-photometry centered on the nuclei. In the connecting bridge, the mid-infrared imaging reveals dust grains intermixed with the atomic hydrogen gas. The heating mechanism for the hot dust is likely to be UV photons diffusing out from the galactic disks and the H II complex located along the extreme northeastern portion of the bridge: The dust emission, or mid-infrared intensity per atomic hydrogen column density ratio, is consistent with heating from the local (bridge) interstellar radiation field.; Comment: see http://spider.ipac.caltech.edu/staff/jarrett/papers/vv254/

Supersonic Line Broadening within Young and Massive Super Star Clusters

Tenorio-Tagle, G.; Wunsch, R.; Silich, S.; Munoz-Tunon, C.; Palous, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/11/2009
Relevância na Pesquisa
35.69%
The origin of supersonic infrared and radio recombination nebular lines often detected in young and massive superstar clusters are discussed. We suggest that these arise from a collection of repressurizing shocks (RSs), acting effectively to re-establish pressure balance within the cluster volume and from the cluster wind which leads to an even broader although much weaker component. The supersonic lines are here shown to occur in clusters that undergo a bimodal hydrodynamic solution (Tenorio-Tagle et al. 2007), that is within clusters that are above the threshold line in the mechanical luminosity or cluster mass vs the size of the cluster (Silich et al. 2004). The plethora of repressurizing shocks is due to frequent and recurrent thermal instabilities that take place within the matter reinserted by stellar winds and supernovae. We show that the maximum speed of the RSs and of the cluster wind, are both functions of the temperature reached at the stagnation radius. This temperature depends only on the cluster heating efficiency ($\eta$). Based on our two dimensional simulations (Wunsch et al. 2008) we calculate the line profiles that result from several models and confirm our analytical predictions. From a comparison between the predicted and observed values of the half-width zero intensity of the two line components we conclude that the thermalization efficiency in SSC's above the threshold line must be lower than 20%.; Comment: 17 pages...

Optical Versus Mid-Infrared Spectroscopic Classification of Ultraluminous Infrared Galaxies

Taniguchi, Yoshiaki; Yoshino, Akira; Ohyama, Youichi; Nishiura, Shingo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/10/1998
Relevância na Pesquisa
25.82%
The origin of huge infrared luminosities of ultraluminous infrared galaxies (ULIGs) is still in question. Recently, Genzel et al. made mid-infrared (MIR) spectroscopy of a large number of ULIGs and found that the major energy source in them is massive stars formed in the recent starburst activity; i.e., $\sim$ 70% -- 80% of the sample are predominantly powered by the starburst. However, it is known that previous optical spectroscopic observations showed that the majority of ULIGs are classified as Seyferts or LINERs (low-ionization nuclear emission-line regions). In order to reconcile this difference, we compare types of emission-line activity for a sample of ULIGs which have been observed in both optical and MIR. We confirm the results of previous studies that the majority of ULIGs classified as LINERs based on the optical emission-line diagnostics turn to be starburst-dominated galaxies based on the MIR ones. Since the MIR spectroscopy can probe more heavily-reddened, inner parts of the ULIGs, it is quite unlikely that the inner parts are powered by the starburst while the outer parts are powered by non-stellar ionization sources. The most probable resolution of this dilemma is that the optical emission-line nebulae with the LINER properties are powered predominantly by shock heating driven by the superwind activity; i.e....

Photoelectric heating and [CII] cooling in translucent clouds: results for cloud models based on simulations of compressible MHD turbulence

Juvela, M.; Padoan, P.; Jimenez, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
25.86%
The photoelectric heating is believed to be the main heating mechanism in cool HI clouds. The heating rate can be estimated through observations of the [CII] line emission, since this is the main coolant in regions where the photoelectric effect dominates the heating. Comparison of the [CII] emission with the far-infrared (FIR) emission allows to constrain the efficiency of the photoelectric heating, using model calculations that take into account the strength of the radiation field. Recent [CII] observations carried out with the ISO satellite have made this study possible. In this work we study the correlation between FUV absorption and FIR emission using three-dimensional models. The density distributions are obtained with numerical simulations of compressible magneto-hydrodynamic turbulence, with rms sonic Mach numbers 0.6

Detection of H2 pure rotational line emission from the GG~Tau binary system

Thi, Wing-Fai; van Dishoeck, Ewine F.; Blake, Geoffrey A.; van Zadelhoff, Gerd-Jan; Hogerheijde, Michiel R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/06/1999
Relevância na Pesquisa
35.66%
We present the first detection of the low-lying pure rotational emission lines of H2 from circumstellar disks around T~Tauri stars, using the Short Wavelength Spectrometer on the Infrared Space Observatory. These lines provide a direct measure of the total amount of warm molecular gas in disks. The J=2->0 S(0) line at 28.218 mum and the J=3->1 S(1) line at 17.035 mum have been observed toward the double binary system GG Tau. Together with limits on the J=5->3 S(3) and J=7->5 S(5) lines, the data suggest the presence of gas at T_kin=110+-10 K with a mass of (3.6+-2.0)x10^-3 M_sol (3sigma). This amounts to ~3% of the total gas + dust mass of the circumbinary disk as imaged by millimeter interferometry, but is larger than the estimated mass of the circumstellar disk(s). Possible origins for the warm gas seen in H2 are discussed in terms of photon and wind-shock heating mechanisms of the circumbinary material, and comparisons with model calculations are made.; Comment: 14 pages including 1 figure. To appear in Astrophysical Journal Letters

CO J=2-1 line emission in cluster galaxies at z~1: fueling star formation in dense environments

Wagg, Jeff; Pope, Alexandra; Alberts, Stacey; Armus, Lee; Brodwin, Mark; Bussmann, Robert S.; Desai, Vandana; Dey, Arjun; Jannuzi, Buell; Floc'h, Emeric Le; Melbourne, Jason; Stern, Daniel
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/04/2012
Relevância na Pesquisa
25.82%
We present observations of CO J=2-1 line emission in infrared-luminous cluster galaxies at z~1 using the IRAM Plateau de Bure Interferometer. Our two primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie within 2 Mpc of the centers of two massive (>10^14 Msun) galaxy clusters. CO line emission is not detected in either DOG. We calculate 3-sigma upper limits to the CO J=2-1 line luminosities, L'_CO < 6.08x10^9 and < 6.63x10^9 K km/s pc^2. Assuming a CO-to-H_2 conversion factor derived for ultraluminous infrared galaxies in the local Universe, this translates to limits on the cold molecular gas mass of M_H_2 < 4.86x10^9 Msun and M_H_2 < 5.30x10^9 Msun. Both DOGs exhibit mid-infrared continuum emission that follows a power-law, suggesting that an AGN contributes to the dust heating. As such, estimates of the star formation efficiencies in these DOGs are uncertain. A third cluster member with an infrared luminosity, L_IR < 7.4x10^11 Lsun, is serendipitously detected in CO J=2-1 line emission in the field of one of the DOGs located roughly two virial radii away from the cluster center. The optical spectrum of this object suggests that it is likely an obscured AGN, and the measured CO line luminosity is L'_CO = (1.94 +/- 0.35)x10^10 K km/s pc^2...

Resolving the Far-IR Line Deficit: Photoelectric Heating and Far-IR Line Cooling in NGC 1097 and NGC 4559

Croxall, Kevin V.; Smith, J. D.; Wolfire, M. G.; Roussel, H.; Sandstrom, K. M.; Draine, B. T.; Aniano, G.; Dale, D. A.; Armus, L.; Beirão, P.; Helou, G.; Bolatto, A. D.; Appleton, P. N.; Brandl, B. R.; Calzetti, D.; Crocker, A. F.; Galametz, M.; Groves,
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/01/2012
Relevância na Pesquisa
25.93%
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 ISM over a large range of infrared surface brightness, on sub-kiloparsec scales, we employ line maps of [C \ii] 158 $\mu$m, [O \one] 63 $\mu$m, and [N \ii] 122 $\mu$m in NGC 1097 and NGC 4559, obtained with the PACS spectrometer onboard {\it Herschel}. We matched new observations to existing Spitzer-IRS 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, ([C \ii] + [O \one])/TIR, decreases as the far-infrared color, $\nu f_\nu$(70 $\mu$m)/$\nu f_\nu$(100 $\mu$m), increases. In contrast, the ratio of far-infrared (far-IR) cooling to total PAH emission, ([C \ii] + [O \one])/PAH, is a near constant $\sim$6% over a wide range of far-infrared color, 0.5 \textless\ $\nu f_\nu$(70 $\mu$m)/$\nu f_\nu$(100 $\mu$m) $\lesssim$ 0.95. In the warmest regions, where $\nu f_\nu$(70 $\mu$m)/$\nu f_\nu$(100 $\mu$m) $\gtrsim$ 0.95, the ratio ([C \ii] + [O \one])/PAH drops rapidly to 4%. We derived representative values of the local UV radiation density, $G_0$, and the gas density...

Resolving the Far-IR Line Deficit: Photoelectric Heating and Far-IR Line Cooling in NGC 1097 and NGC 4559

Croxall, Kevin V.; Armus, L.; Beirão, P.; Helou, G.; Appleton, P. N.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/03/2012
Relevância na Pesquisa
25.92%
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 [C II] 158 μm, [O I] 63 μm, and [N II] 122 μm 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, ([C II] + [O I])/TIR, decreases as the far-infrared (far-IR) color, ν_f ν(70 μm) νf_ν(100 μm), increases. In contrast, the ratio of far-IR cooling to total PAH emission, ([C II] + [O I])/PAH, is a near constant ~6% over a wide range of far-IR color, 0.5 < νf_ν(70 μm) νf_ν(100 μm) ≾ 0.95. In the warmest regions, where νf_ν(70 μm) νf_ν(100 μm) ≳ 0.95, the ratio ([C II] + [OI])/PAH drops rapidly to 4%. We derived representative values of the local ultraviolet radiation density, G_0, and the gas density, n_H, by comparing our observations to models of photodissociation regions. The ratio G_0/n_H...

Detection of H_2 Pure Rotational Line Emission from the GG Tauri Binary System

Thi, Wing-Fai; van Dishoeck, Ewine F.; Blake, Geoffrey A.; van Zadelhoff, Gerd-Jan; Hogerheijde, Michiel R.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 10/08/1999
Relevância na Pesquisa
35.66%
We present the first detection of the low-lying pure rotational emission lines of H_2 from circumstellar disks around T Tauri stars, using the Short Wavelength Spectrometer on the Infrared Space Observatory. These lines provide a direct measure of the total amount of warm molecular gas in disks. The J = 2 → 0 S(0) line at 28.218 μm and the J = 3 → 1 S(1) line at 17.035 μm have been observed toward the double binary system GG Tau. Together with limits on the J = 5 → 3 S(3) and J = 7 → 5 S(5) lines, the data suggest the presence of gas at T_(kin) ≈ 110 ± 10 K with a mass of (3.6 ± 2.0) × 10^(-3) M_☉ (±3 σ). This amounts to ~3% of the total gas + dust mass of the circumbinary disk as imaged by millimeter interferometry, but it is larger than the estimated mass of the circumstellar disk(s). Possible origins for the warm gas seen in H_2 are discussed in terms of photon and wind-shock heating mechanisms of the circumbinary material, and comparisons with model calculations are made.

Searching for gas emission lines in Spitzer Infrared Spectrograph (IRS) spectra of young stars in Taurus

Baldovin-Saavedra, C.; Audard, M.; Güedel, M.; Rebull, L. M.; Padgett, D. L.; Skinner, S. L.; Carmona, A.; Glauser, A. M.; Fajardo-Acosta, S. B.
Fonte: EDP Sciences Publicador: EDP Sciences
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /04/2011
Relevância na Pesquisa
25.83%
Context. Our knowledge of circumstellar disks has traditionally been based on studies of dust. However, gas dominates the disk mass and its study is key to our understanding of accretion, outflows, and ultimately planet formation. The Spitzer Space Telescope provides access to gas emission lines in the mid-infrared, providing crucial new diagnostics of the physical conditions in accretion disks and outflows. Aims. We seek to identify gas emission lines in mid-infrared spectra of 64 pre-main-sequence stars in Taurus. Using line luminosities and other known star-disk-outflow parameters, we aim to identify correlations that will help to constrain gas heating, excitation mechanisms, and the line formation. Methods. We have based our study on Spitzer observations using the Infrared Spectrograph (IRS), mainly with the high-resolution modules. Line luminosities (or 3σ upper limits) have been obtained by fitting Gaussian profiles to the lines. We have further searched for correlations between the line luminosities and different parameters related to the star-disk system. Results. We have detected H_2 (17.03, 28.22 μm) emission in 6 objects, [Ne II] (12.81 μm) emission in 18 objects, and [Fe II] (17.93, 25.99 μm) emission in 7 objects. [Ne II] detections are found primarily in Class II objects. The luminosity of the [Ne II] line (L_(NeII)) is in general higher for objects known to drive jets than for those without known jets...

Cool dust heating and temperature mixing in nearby star-forming galaxies

Hunt, L. K.; Draine, B. T.; Bianchi, S.; Gordon, K. D.; Aniano, G.; Calzetti, D.; Dale, D. A.; Helou, G.; Hinz, J. L.; Kennicutt, R. C.; Roussel, H.; Wilson, C. D.; Bolatto, A.; Boquien, M.; Croxall, K. V.; Galametz, M.; Gil de Paz, A.; Koda, J.; Muñoz-M
Fonte: EDP Sciences Publicador: EDP Sciences
Tipo: Article; PeerReviewed Formato: application/pdf; application/pdf
Publicado em /04/2015
Relevância na Pesquisa
25.83%
Physical conditions of the interstellar medium in galaxies are closely linked to the ambient radiation field and the heating of dust grains. In order to characterize dust properties in galaxies over a wide range of physical conditions, we present here the radial surface brightness profiles of the entire sample of 61 galaxies from Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH). The main goal of our work is the characterization of the grain emissivities, dust temperatures, and interstellar radiation fields (ISRFs) responsible for heating the dust. We first fit the radial profiles with exponential functions in order to compare stellar and cool-dust disk scalelengths, as measured by 3.6 μm and 250 μm surface brightnesses. Our results show that the stellar and dust scalelengths are comparable, with a mean ratio of 1.04, although several galaxies show dust-to-stellar scalelength ratios of 1.5 or more. We then fit the far-infrared spectral energy distribution (SED) in each annular region with single-temperature modified blackbodies using both variable (MBBV) and fixed (MBBF) emissivity indices β, as well as with physically motivated dust models. The KINGFISH profiles are well suited to examining trends of dust temperature T_(dust) and β because they span a factor of ~200 in the ISRF intensity heating the bulk of the dust mass...

CO J = 2-1 Line Emission in Cluster Galaxies at z ~ 1: Fueling Star Formation in Dense Environments

Wagg, Jeff; Pope, Alexandra; Alberts, Stacey; Armus, Lee; Brodwin, Mark; Bussmann, Robert S.; Desai, Vandana; Dey, Arjun; Jannuzi, Buell T.; Le Floc'h, Emeric; Melbourne, Jason; Stern, Daniel
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 20/06/2012
Relevância na Pesquisa
25.82%
We present observations of CO J = 2–1 line emission in infrared-luminous cluster galaxies at z ∼ 1 using the IRAM Plateau de Bure Interferometer. Our two primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie within 2Mpc of the centers of two massive (>10^(14)M_☉) galaxy clusters. CO line emission is not detected in either DOG. We calculate 3σ upper limits to the CO J = 2–1 line luminosities, L_(CO) < 6.08×10^9 and <6.63×10^9 K km s^(−1) pc^2. Assuming a CO-to-H_2 conversion factor derived for ultraluminous infrared galaxies in the local universe, this translates to limits on the cold molecular gas mass of M_(H2) < 4.86×10^9 M_☉ and M_(H2) < 5.30×10^9 M_☉. Both DOGs exhibit mid-infrared continuum emission that follows a power law, suggesting that an active galactic nucleus (AGN) contributes to the dust heating. As such, estimates of the star formation efficiencies in these DOGs are uncertain. A third cluster member with an infrared luminosity, L_(IR) < 7.4×10^(11)L_☉, is serendipitously detected in CO J = 2–1 line emission in the field of one of the DOGs located roughly two virial radii away from the cluster center. The optical spectrum of this object suggests that it is likely an obscured AGN...

The Impact of the Massive Young Star GL 2591 on Its Circumstellar Material: Temperature, Density, and Velocity Structure

van der Tak, Floris F. S.; van Dishoeck, Ewine F.; Evans, Neal J., II; Bakker, Eric J.; Blake, Geoffrey A.
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 10/09/1999
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The temperature, density, and kinematics of the gas and dust surrounding the luminous (2 × 10^4 L_☉) young stellar object GL 2591 are investigated on scales as small as ~100 AU, probed by 4.7 μm absorption spectroscopy, to over 60,000 AU, probed by single-dish submillimeter spectroscopy. These two scales are connected by interferometric 86-115 and 226 GHz images of size 30,000 AU and resolution 2000 AU in continuum and molecular lines. The data are used to constrain the physical structure of the envelope and investigate the influence of the young star on its immediate surroundings. The infrared spectra at λ/Δλ ≈ 40,000 indicate an LSR velocity of the ^(13)CO rovibrational lines of -5.7 ± 1.0 km s^(-1), consistent with the velocity of the rotational lines of CO. In infrared absorption, the ^(12)CO lines show wings out to much higher velocities, ≈-200 km s^(-1), than are seen in the rotational emission lines, which have a total width of ≈75 km s^(-1). This difference suggests that the outflow seen in rotational lines consists of envelope gas entrained by the ionized jet seen in Brγ and [S II] emission. The outflowing gas is warm, T > 100 K, since it is brighter in CO J = 6 → 5 than in lower-J CO transitions. The dust temperature due to heating by the young star has been calculated self-consistently as a function of radius for a power-law density distribution n = n_0r^(-α)...