Showing papers by "George H. Rieke published in 2004"
TL;DR: The Spitzer Space Telescope, NASA's great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit as mentioned in this paper.
Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical, and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first 6 months of the Spitzer mission.
3,177 citations
TL;DR: The Multiband Imaging Photometer for Spitzer (MIPS) as discussed by the authors provides long-wavelength capability for the mission in imaging bands at 24, 70, and 160?m and measurements of spectral energy distributions between 52 and 100?m at a spectral resolution of about 7%.
Abstract: The Multiband Imaging Photometer for Spitzer (MIPS) provides long-wavelength capability for the mission in imaging bands at 24, 70, and 160 ?m and measurements of spectral energy distributions between 52 and 100 ?m at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point-spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The 24 ?m array has excellent photometric properties, and measurements with rms relative errors of about 1% can be obtained. The two longer-wavelength arrays use detectors with poor photometric stability, but a system of onboard stimulators used for relative calibration, combined with a unique data pipeline, produce good photometry with rms relative errors of less than 10%.
2,370 citations
TL;DR: In this article, the authors present the results from deep 24 μm imaging from Spitzer surveys, which include ≈5 × 10^4 sources to an 80% completeness of ≃ 60 μJy.
Abstract: Galaxy source counts in the infrared provide strong constraints on the evolution of the bolometric energy output from distant galaxy populations. We present the results from deep 24 μm imaging from Spitzer surveys, which include ≈5 × 10^4 sources to an 80% completeness of ≃ 60 μJy. The 24 μm counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with a super-Euclidean rate between 0.4 and 4 mJy, and converge below ~0.3 mJy. The 24 μm counts exceed expectations from nonevolving models by a factor of ≳10 at S_ν ~ 0.1 mJy. The peak in the differential number counts corresponds to a population of faint sources that is not expected from predictions based on 15 μm counts from the Infrared Space Observatory. We argue that this implies the existence of a previously undetected population of infrared-luminous galaxies at z ~ 1-3. Integrating the counts to 60 μJy, we derive a lower limit on the 24 μm background intensity of 1.9 ± 0.6 nW m^(-2) sr^(-1) of which the majority (~60%) stems from sources fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60 μJy contribute 0.8^(+0.9)_(-0.4) nW m^(-2) sr^(-1) to the background, which provides an estimate of the total 24 μm background of 2.7^(+1.1)_(-0.7) nW m^(-2) sr^(-1).
347 citations
TL;DR: In this article, the authors present the results from deep 24 micron imaging from Spitzer surveys, which include approximately 50,000 sources to an 80% completeness of 60 uJy.
Abstract: Galaxy source counts in the infrared provide strong constraints on the evolution of the bolometric energy output from distant galaxy populations. We present the results from deep 24 micron imaging from Spitzer surveys, which include approximately 50,000 sources to an 80% completeness of 60 uJy. The 24 micron counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with a super-Euclidean rate between 0.4 - 4 mJy, and converge below 0.3 mJy. The 24 micron counts exceed expectations from non-evolving models by a factor >10 at 0.1 mJy. The peak in the differential number counts corresponds to a population of faint sources that is not expected from predictions based on 15 micron counts from ISO. We argue that this implies the existence of a previously undetected population of infrared-luminous galaxies at z ~ 1-3. Integrating the counts to 60 uJy, we derive a lower limit on the 24 micron background intensity of 1.9 +/- 0.6 nW m-2 sr-1 of which the majority (~ 60%) stems from sources fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60 uJy contribute 0.8 {+0.9/-0.4} nW m-2 sr-1 to the background, which provides an estimate of the total 24 micron background of 2.7 {+1.1/-0.7} nW m-2 sr-1.
319 citations
TL;DR: The Spitzer Space Telescope was used to study the mid-to far-infrared properties of NGC 300 and to compare dust emission to Hα to elucidate the heating of the interstellar medium and the star formation cycle at scales smaller than 100 pc as mentioned in this paper.
Abstract: The Spitzer Space Telescope was used to study the mid- to far-infrared properties of NGC 300 and to compare dust emission to Hα to elucidate the heating of the interstellar medium (ISM) and the star formation cycle at scales smaller than 100 pc. The new data allow us to discern clear differences in the spatial distribution of 8 μm dust emission with respect to 24 μm dust and to H II regions traced by Hα light. The 8 μm emission highlights the rims of H II regions, and the 24 μm emission is more strongly peaked in star-forming regions than 8 μm. We confirm the existence and approximate amplitude of interstellar dust emission at 4.5 μm, detected statistically in Infrared Space Observatory (ISO) data, and conclude it arises in star-forming regions. When averaging over regions larger than ~1 kpc, the ratio of Hα to aromatic feature emission in NGC 300 is consistent with the values observed in disks of spiral galaxies. The mid- to far-infrared spectral energy distribution of dust emission is generally consistent with pre-Spitzer models.
312 citations
TL;DR: In this article, an updated phenomenological galaxy evolution model was proposed to fit the Spitzer 24, 70, and 160 μm number counts, as well as all the previous mid- and far-infrared observations.
Abstract: We present an updated phenomenological galaxy evolution model to fit the Spitzer 24, 70, and 160 μm number counts, as well as all the previous mid- and far-infrared observations. Only a minor change of the comoving luminosity density distribution in the previous model (Lagache, Dole, & Puget), combined with a slight modification of the starburst template spectra mainly between 12 and 30 μm, are required to fit all the data available. We show that the peak in the Spitzer Multiband Imaging Photometer 24 μm counts is dominated by galaxies with redshift between 1 and 2, with a nonnegligible contribution from the z ≥ 2 galaxies (~30% at S = 0.2 mJy). The very close agreement between the model and number counts at 15 and 24 μm strikingly implies that (1) the polycyclic aromatic hydrocarbon features remain prominent in the redshift band 0.5-2.5 and (2) the IR energy output has to be dominated by ~3 × 1011 L⊙ to ~3 × 1012 L⊙ galaxies from redshift 0.5 to 2.5. Combining Spitzer with Infrared Space Observatory deep cosmological surveys gives for the first time an unbiased view of the infrared universe from z = 0 to 2.5.
277 citations
TL;DR: In this article, an overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided, as well as initial results of the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position.
Abstract: The Infrared Array Camera (IRAC) shallow survey covers 8.5 deg2 in the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes ≈370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 σ limits of 6.4, 8.8, 51, and 50 μJy at 3.6, 4.5, 5.8, and 8 μm, respectively, including some with unusual spectral energy distributions.
244 citations
TL;DR: The Spitzer Space Telescope, NASA's great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit as discussed by the authors.
Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first six months of the Spitzer mission.
174 citations
TL;DR: In this paper, the authors presented Spitzer Space Telescope early release observations of Fomalhaut, a nearby A-type star with dusty circumstellar debris, spatially resolved at 24, 70, and 160 m using the Multiband Imaging Photometer for Spitzer (MIPS).
Abstract: We present Spitzer Space Telescope early release observations of Fomalhaut, a nearby A-type star with dusty circumstellar debris. The disk is spatially resolved at 24, 70, and 160 � m using the Multiband Imaging Photometer for Spitzer (MIPS). While the disk orientation and outer radius are comparable to values measured in the submillimeter, the disk inner radius cannot be precisely defined: the central hole in the submillimeter ring is at least partially filled with emission from warm dust, seen inSpitzerInfrared Spectrograph (IRS) 17.5‐34 � m spectra and MIPS 24 � m images. The disk surface brightness becomes increasingly asymmetric toward shorter wavelengths, with the south-southeast ansa always brighter than the north-northwest one. This asymmetry may reflect perturbations on the disk by an unseen interior planet. Subject headingg circumstellar matter — infrared: stars — planetary systems — stars: individual (Fomalhaut)
164 citations
TL;DR: In this article, 3.6-24 μm Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 μm by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies (hereafter SMGs).
Abstract: We present 3.6-24 μm Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 μm by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies (hereafter SMGs). Owing to the coarse resolution of submillimeter/millimeter cameras, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multiwavelength catalogs to show that the overlap between 24 and 1200 μm must be close to complete at these flux levels. We find that all (4/4) of the most secure ≥4 σ SMGs have ≥4 σ counterparts at 1.4 GHz, while the fraction drops to 7/9 using all ≥3 σ SMGs. We show that combining mid-infrared (MIR) and marginal (≥3 σ) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the MIR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of an S24 μm/S8 μm versus S8 μm/S4.5 μm color-color plot as a diagnostic for this purpose. However, we conclude that the majority (~75%) of SMGs have rest-frame mid/far-IR spectral energy distributions commensurate with obscured starbursts. Sensitive 24 μm observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies, complementing what is possible via deep radio imaging.
137 citations
TL;DR: In this paper, the authors search for infrared excesses due to debris disks toward 26 FGK field stars known from radial velocity (RV) studies to have one or more planets.
Abstract: As part of a large Spitzer/MIPS GTO program, we have searched for infrared excesses due to debris disks toward 26 FGK field stars known from radial velocity (RV) studies to have one or more planets. While none of these stars show excesses at 24um, we have detected 70um excesses around 6 stars at the 3-sigma confidence level. The excesses are produced by cool material (< 100 K) located beyond 10 AU, well outside the "habitable zones" of these systems and consistent with the presence of Kuiper Belt analogues with ~100 times more emitting surface area than in our own planetary system.
These planet-bearing stars are, by selection for RV studies, typically older than 1 Gyr, and the stars identified here with excesses have a median age of 4 Gyr. We find a preliminary correlation of both the frequency and the magnitude of dust emission with the presence of known planets. These are the first stars outside the solar system identified as having both well-confirmed planetary systems and well-confirmed IR excesses.
TL;DR: In this article, the authors present an empirical infrared spectral library of 218 red stars, spanning a range of [Fe/H] from ~-2.2 to ~+0.3.
Abstract: We present an empirical infrared spectral library of medium-resolution (R ≈ 2000-3000) H (1.6 μm) and K (2.2 μm) band spectra of 218 red stars, spanning a range of [Fe/H] from ~-2.2 to ~+0.3. The sample includes Galactic disk stars, bulge stars from Baade's window, and red giants from Galactic globular clusters. We report the values of 19 indices covering 12 spectral features measured from the spectra in the library. Finally, we derive calibrations to estimate the effective temperature, and diagnostic relationships to determine the luminosity classes of individual stars from near-infrared spectra. This paper is part of a larger effort aimed at building a near-IR spectral library to be incorporated in population synthesis models, as well as at testing synthetic stellar spectra.
TL;DR: In this article, the authors derived galaxy source counts at 70 and 160 μm using the Multiband Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field-South (CDF-S) and other fields.
Abstract: We derive galaxy source counts at 70 and 160 μm using the Multiband Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field-South (CDF-S) and other fields. At 70 μm, our observations extend upward about 2 orders of magnitude in flux density from a threshold of 15 mJy, and at 160 μm they extend about an order of magnitude upward from 50 mJy. The counts are consistent with previous observations on the bright end. Significant evolution is detected at the faint end of the counts in both bands, by factors of 2-3 over no-evolution models. This evolution agrees well with models that indicate that most of the faint galaxies lie at redshifts between 0.7 and 0.9. The new Spitzer data already resolve about 23% of the cosmic far-infrared background at 70 μm and about 7% at 160 μm.
TL;DR: In this paper, the authors presented Spitzer Space Telescope imaging observations at 3.6, 4.5, 5.8, 8.0, and 24 m of the SCUBA submillimeter sources and VLA radio sources in a 5'? 5' area in the Lockman Hole East region.
Abstract: We present Spitzer Space Telescope imaging observations at 3.6, 4.5, 5.8, 8.0, and 24 ?m of the SCUBA submillimeter sources and ?Jy VLA radio sources in a 5' ? 5' area in the Lockman Hole East region. Out of the ~40 SCUBA/VLA sources in the field, Spitzer counterparts were detected for nearly all except for the few low-weight SCUBA detections. We show that the majority (80%-90%) of the detected sources are cold (i.e., starburst-like) infrared-luminous galaxies (LIR > 1011 L?) at redshift 0.5 < z < 3.5, whose star-formation rate density (SFRD) is comparable to that of the optically selected star-forming galaxies.
TL;DR: In this paper, the authors present Spitzer observations in five wavebands between 3.6 and 24um of an unbiased sample of 9 luminous, dusty galaxies selected at 1200um by the MAMBO camera on the IRAM 30m telescope, a population akin to the well-known submm or ''SCUBA' galaxies (hereafter SMGs).
Abstract: We present Spitzer observations in five wavebands between 3.6 and 24um of an unbiased sample of 9 luminous, dusty galaxies selected at 1200um by the MAMBO camera on the IRAM 30-m telescope, a population akin to the well-known submm or `SCUBA' galaxies (hereafter SMGs). Owing to the coarse resolution of submm/mm instrumentation, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multi-wavelength catalogs to show that the overlap between 24 and 1200um must be close to complete at these flux levels. We find that all (4/4) of the most secure >=4sigma SMGs have robust >=4sigma counterparts at 1.4GHz, while the fraction drops to 7/9 using all >=3sigma SMGs. We show that combining mid-IR and marginal (>=3sigma) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the mid-IR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of a S(24um)/S(8um) vs S(8um)/S(4.5um) color-color plot as a diagnostic for this purpose. However, we conclude that the majority (~75%) of SMGs have rest-frame mid-/far-IR SEDs commensurate with obscured starbursts. Sensitive 24-um observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies, complementing what is possible via deep radio imaging.
TL;DR: In this paper, the authors reported the detection of a z~7 galaxy strongly lensed by the massive galaxy cluster Abell 2218 (z=0.175) at 3.6 and 4.5 um using the Spitzer Observatory and at 1.1 am using the Hubble Space Telescope.
Abstract: We report the detection of a z~7 galaxy strongly lensed by the massive galaxy cluster Abell 2218 (z=0.175) at 3.6 and 4.5 um using the Spitzer Observatory and at 1.1 um using the Hubble Space Telescope. The new data indicate a refined photometric redshift in the range of 6.6-6.8 depending on the presence of Ly-alpha emission. The spectral energy distribution is consistent with having a significant Balmer break, suggesting that the galaxy is in the poststarburst stage with an age of at least ~50 Myr and quite possibly a few hundred Myr. This suggests the possibility that a mature stellar population is already in place at such a high redshift. Compared with typical Lyman break galaxies at z~3-4, the stellar mass is an order of magnitude smaller (~10^{9} Msun), but the specific star formation rate (star formation rate/M_{star}) is similarly large (> 10^{-9} yr^{-1}), indicating equally vigorous star-forming activity.
TL;DR: In this article, the authors obtained thermal images and spectra of 29P/Schwassmann-Wachmann 1 in late 2003 November and revealed an extensive coma with an estimated dust production rate of 50 kg s-1.
Abstract: We obtained thermal images and spectra of comet and Centaur object 29P/Schwassmann-Wachmann 1 in late 2003 November. Images at 8, 24, and 70 ?m reveal an extensive coma. At 24 ?m the coma extends at least 8' from the nucleus and exhibits a single jet. The dust production rate is estimated as 50 kg s-1. The 24 to 70 ?m color temperature of the coma is 160 K. The debris trail is also detected at 24 ?m and has an optical depth of ~(7 ? 3) ? 10-9. Thermal models fitted to photometry at 8, 24, and 70??m indicate a nuclear radius of 27 ? 5 km, larger than all previous size estimates, and a geometric albedo of 0.025 ? 0.01, lower than any other Centaur object, but consistent with other comets. Analysis of the jet morphology indicates a rotation period in excess of 60 days. The spectra reveal features at 11.3 and 34 ?m, which are tentatively identified as emission from olivine, including forsterite. This is the first identification of the minerology of the dust emitted by a Centaur object.
TL;DR: Far-infrared and molecular line observations demonstrate that most of the detected submillimetre emission originates from interstellar dust in a molecular cloud complex located in the line of sight between the Earth and Cas A, and is therefore not associated with the remnant.
Abstract: A large amount (about three solar masses) of cold (18 K) dust in the prototypical type II supernova remnant Cassiopeia A was recently reported. It was concluded that dust production in type II supernovae can explain how the large quantities (approximately 10(8) solar masses) of dust observed in the most distant quasars could have been produced within only 700 million years after the Big Bang. Foreground clouds of interstellar material, however, complicate the interpretation of the earlier submillimetre observations of Cas A. Here we report far-infrared and molecular line observations that demonstrate that most of the detected submillimetre emission originates from interstellar dust in a molecular cloud complex located in the line of sight between the Earth and Cas A, and is therefore not associated with the remnant. The argument that type II supernovae produce copious amounts of dust is not supported by the case of Cas A, which previously appeared to provide the best evidence for this possibility.
TL;DR: In this article, the authors used the source counts measured with the Multiband Imaging Photometer for Spitzer at 24, 70, and 160 μm to determine the 5 σ confusion limits due to extragalactic sources.
Abstract: We use the source counts measured with the Multiband Imaging Photometer for Spitzer at 24, 70, and 160 μm to determine the 5 σ confusion limits due to extragalactic sources: 56 μJy, 3.2 mJy, and 40 mJy at 24, 70, and 160 μm, respectively. We also make predictions for confusion limits for a number of proposed far-infrared missions of larger aperture (3.5-10 m diameter).
TL;DR: In this paper, the authors show that He I 2.06 μm/Brγ and [O III]/Hβ are generally unreliable diagnostics in starbursts.
Abstract: Determining the properties of starbursts requires spectral diagnostics of their ultraviolet radiation fields, to test whether very massive stars are present. We test several such diagnostics, using new models of line ratio behavior combining CLOUDY, Starburst99, and up-to-date spectral atlases. For six galaxies we obtain new measurements of He I 1.7 μm/Br10, a difficult to measure but physically simple (and therefore reliable) diagnostic. We obtain new measurements of He I 2.06 μm/Brγ in five galaxies. We find that He I 2.06 μm/Brγ and [O III]/Hβ are generally unreliable diagnostics in starbursts. The heteronuclear and homonuclear mid-infrared line ratios (notably [Ne III] 15.6 μm/[Ne II] 12.8 μm) consistently agree with each other and with He I 1.7 μm/Br10; this argues that the mid-infrared line ratios are reliable diagnostics of spectral hardness. In a sample of 27 starbursts, [Ne III]/[Ne II] is significantly lower than model predictions for a Salpeter initial mass function (IMF) extending to 100 M☉. Plausible model alterations strengthen this conclusion. By contrast, the low-mass and low-metallicity galaxies II Zw 40 and NGC 5253 show relatively high neon line ratios, compatible with a Salpeter slope extending to at least ~40-60 M☉. One solution for the low neon line ratios in the high-metallicity starbursts would be that they are deficient in 40 M☉ stars compared to a Salpeter IMF. An alternative explanation, which we prefer, is that massive stars in high-metallicity starbursts spend much of their lives embedded within ultracompact H II regions that prevent the near- and mid-infrared nebular lines from forming and escaping. This hypothesis has important consequences for starburst modeling and interpretation.
TL;DR: In this article, the authors investigated the variation of the ultraviolet (UV), Hα, and infrared (IR) luminosities and star formation rate (SFR) indicators across the face of M81 using the MIPS images and archival UV and Hα images.
Abstract: We present Multiband Imaging Photometer for Spitzer (MIPS) observations of M81 at 24, 70, and 160 μm. The grand design nature of M81 is clearly seen, showing two well-resolved spiral arms containing numerous bright star-forming regions. The MIPS images reveal a significant amount of cold dust associated with the spiral arms. We investigate the variation of the ultraviolet (UV), Hα, and infrared (IR) luminosities and star formation rate (SFR) indicators across the face of M81 using the MIPS images and archival UV and Hα images. For regions in M81, we find that UV and Hα SFRs (uncorrected for dust attenuation) are always lower than the IR SFR. The cause of this behavior is dust attenuation and/or using SFR calibrations appropriate for entire galaxies, not regions in galaxies. The characteristics of the dust attenuation for the regions indicate the dust grains and/or geometry are different from those in starburst galaxies. The behavior of the infrared-radio correlation in M81 is seen to vary from the global average, with variations correlated with the morphology of M81.
TL;DR: In this article, the authors presented new images of the supernova remnant (SNR) Cas A observed in the 24 and 70 μm bands of the Spitzer Space Telescope (Spitzer).
Abstract: We present new images of the supernova remnant (SNR) Cas A observed in the 24 and 70 μm bands of the Spitzer Space Telescope (Spitzer). The IR emission correlates well with the Si X-ray and optical [S II] emission but poorly with either the synchrotron-dominated radio structure or the continuum X-ray emission. The IR is therefore dominated by thermal emission from dust within the SNR and associated with emission-line gas inside the reverse shock region, confirming earlier IRAS and Infrared Space Observatory results. Supplemented by new photometric measurements from archived Midcourse Space Experiment images, we suggest stochastic heating to model the overall mid- to far-IR spectral energy distribution. The 24 and 70 μm images also reveal a counterjet to the well-known northeast jet feature imaged previously at X-ray, optical, and radio wavelengths. This IR counterjet corresponds well with (optical) fast-moving knots confirming its outflow nature. The opposing jetlike features define a symmetry axis that bisects the SNR and suggest that the supernova explosion was axisymmetric. The IR images also show a region in which the SNR forward shock appears to be propagating into a ~650 M⊙ molecular cloud. The new images also show other details of the surrounding ISM structure, including two groups of knots extending ~6'-12' on either side of the SNR.
University of Arizona1, Spanish National Research Council2, Jet Propulsion Laboratory3, Goddard Space Flight Center4, Max Planck Society5, Space Telescope Science Institute6, Danish Space Research Institute7, Stockholm University8, Dublin Institute for Advanced Studies9, Katholieke Universiteit Leuven10, Paul Scherrer Institute11
TL;DR: The MIRI is the mid-IR instrument for JWST and provides imaging, coronography and low and medium resolution spectroscopy over the 5-28μm band as discussed by the authors.
Abstract: The MIRI is the mid-IR instrument for JWST and provides imaging, coronography and low and medium resolution spectroscopy over the 5-28μm band. In this paper we provide an overview of the key driving requirements and design status.
TL;DR: In this paper, the authors show that the mid-infrared line ratios of starbursts are reliable diagnostics of spectral hardness, consistent with a Salpeter slope extending to at least 40--60 Msol.
Abstract: Determining the properties of starbursts requires spectral diagnostics of their ultraviolet radiation fields, to test whether very massive stars are present. We test several such diagnostics, using new models of line ratio behavior combining Cloudy, Starburst99 and up-to-date spectral atlases. For six galaxies we obtain new measurements of HeI 1.7 um / Brackett 10, a difficult to measure but physically simple (and therefore reliable) diagnostic. We obtain new measurements of HeI 2.06 um / Brackett gamma in five galaxies, and find that it and [OIII]/Hbeta are generally unreliable diagnostics in starbursts. The heteronuclear and homonuclear mid--infrared line ratios (notably [NeIII] 15.6 um / [NeII] 12.8 um) consistently agree with each other and with HeI 1.7 um / Br10; this argues that the mid-infrared line ratios are reliable diagnostics of spectral hardness. In a sample of 27 starbursts, [NeIII]/[NeII] ratios are significantly less excited than model predictions for a Salpeter IMF extending to 100 solar masses. Plausible model alterations strengthen this conclusion. By contrast, the low-mass and low-metallicity galaxies II Zw 40 and NGC 5253 show relatively high neon line ratios, compatible with a Salpeter slope extending to at least 40--60 Msol. One solution for the low neon line ratios in the high--metallicity starbursts would be that they are deficient in >40 Msol stars compared to a Salpeter IMF. An alternative explanation, which we prefer, is that massive stars in high--metallicity starbursts spend much of their lives embedded within ultra--compact HII regions that prevent the near- and mid-infrared nebular lines from forming and escaping. This hypothesis has important consequences for starburst modelling and interpretation.
TL;DR: In this article, multiband imaging photometer for Spitzer (MIPS) observations of M81 at 24, 70, and 160 micron were used to investigate the variation of the ultraviolet (UV), H-alpha, and infrared (IR) luminosities and star formation rate (SFR) indicators across the face of a galaxy.
Abstract: We present Multiband Imaging Photometer for Spitzer (MIPS) observations of M81 at 24, 70, and 160 micron. The grand design nature of M81 is clearly seen, showing two well resolved spiral arms containing numerous bright star forming regions. The MIPS images reveal a significant amount of cold dust associated with the spiral arms. We investigate the variation of the ultraviolet (UV), H-alpha, and infrared (IR) luminosities and star formation rate (SFR) indicators across the face of M81 using the MIPS images and archival UV and H-alpha images. For regions in M81, we find that UV and H-alpha SFRs (uncorrected for dust attenuation) are always lower than the IR SFR. The cause of this behavior is dust attenuation and/or using SFR calibrations appropriate for entire galaxies, not regions in galaxies. The characteristics of the dust attenuation for the regions indicate the dust grains and/or geometry are different from those in starburst galaxies. The behavior of the infrared-radio correlation in M81 is seen to vary from the global average, with variations correlated with the morphology of M81.
TL;DR: In this article, a significant population of sources, likely pre-main-sequence members of the young stellar cluster, are revealed outside the central photoionization region, where they are associated with the densest part of the molecular cloud surrounding the photometric region.
Abstract: We present observations of the star formation region NGC 7129 taken with the Multiband Imaging Photometer for Spitzer (MIPS) A significant population of sources, likely pre-main-sequence members of the young stellar cluster, are revealed outside the central photoionization region Combining Infrared Array Camera (IRAC) and ground-based near-infrared images, we have obtained colors and spectral energy distributions for some 60 objects The [36]-[45] versus [8]-[24] color-color plane shows sources clustered at several different loci, which roughly correspond to the archetypal evolutionary sequence Class 0, I, II, and III We obtain preliminary classifications for 36 objects and find significant numbers of both Class I and II objects Most of the pre-main-sequence candidates are associated with the densest part of the molecular cloud surrounding the photoionization region, indicating active star formation over a broad area outside the central cluster We discuss three Class II candidates that exhibit evidence of inner disk clearing, which would be some of the youngest known examples of a transition from accretion to optically thin quiescent disks
TL;DR: The nearby spiral galaxy NGC 7331 was spectrally mapped from 5 to 38 μm using all modules of Spitzer's Infrared Spectrograph (IRS) as discussed by the authors.
Abstract: The nearby spiral galaxy NGC 7331 was spectrally mapped from 5 to 38 μm using all modules of Spitzer's Infrared Spectrograph (IRS) A strong new dust emission feature, presumed due to polycyclic aromatic hydrocarbons, was discovered at 171 μm The feature's intensity is nearly half that of the ubiquitous 113 μm band The 7-14 μm spectral maps revealed significant variation in the 77 and 113 μm PAH features between the stellar ring and nucleus Weak [O IV] 259 μm line emission was found to be centrally concentrated in the nucleus, with an observed strength of over 10% of the combined neon line flux, indicating an AGN or unusually active massive star photoionization Two [S III] lines fix the characteristic electron density in the H II regions at ne 200 cm-3 Three detected H2 rotational lines, tracing warm molecular gas, together with the observed IR continuum, are difficult to match with standard photodissociation region (PDR) models Either additional PDR heating or shocks are required to simultaneously match lines and continuum
TL;DR: In this article, IRAC imaging of a 47 × 47 area in the Lockman Hole detected over 400 galaxies in the IRAC 3.6 and 4.5 GHz bands, 120 in the 5.8 GHz band, and 80 in the 8.0 GHz band in 30 minutes of observing time.
Abstract: IRAC imaging of a 47 × 47 area in the Lockman Hole detected over 400 galaxies in the IRAC 3.6 and 4.5 μm bands, 120 in the 5.8 μm band, and 80 in the 8.0 μm band in 30 minutes of observing time. Color-color diagrams suggest that about half of these galaxies are at redshifts 0.6 1.3). We also detect IRAC counterparts for six of the seven SCUBA sources and all nine XMM-Newton sources in this area. The detection of the counterparts of the SCUBA sources and galaxies at z > 1.3 demonstrates the ability of IRAC to probe the universe at very high redshifts.
TL;DR: In this paper, the authors obtained images of the obscured massive star-forming region DR 21 using both the IRAC and Multiband Imaging Photometer for Spitzer (MIPS) instruments aboard the Spitzer Space Telescope.
Abstract: We have obtained images of the obscured massive star-forming region DR 21 using both the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) instruments aboard the Spitzer Space Telescope. Our images cover an area of more than half a square degree. The unprecedented high sensitivity and resolution of both IRAC and MIPS allow us to reveal the complexity of this region for the first time. Our images show extended outflows from a dense disk of material. Previously observed molecular outflows from the center of DR 21 are clearly visible in our images and are embedded in a much larger region of diffuse filaments apparently flowing out from DR 21. Many of the point sources in the region seen by Spitzer at 8 and 24 μm are both very obscured and intrinsically red. We discuss the properties of some of these extremely red objects and indicate that they are likely to be Class I or earlier protostars. Other features observed include mid-infrared dark clouds that occasionally appear as swept up features from extremely red objects, including a 15 pc long north-south filament to the south of DR 21 itself.
01 Jan 2004
TL;DR: In this article, the authors used the source counts measured with the Multiband Imaging Photometer for Spitzer (MIPS) at 24, 70, and 160 µm to determine the 5-� confusion limits due to extragalactic sources: 56µJy, 3.2 µm, and 40 µm.
Abstract: We use the source counts measured with the Multiband Imaging Photometer for Spitzer (MIPS) at 24, 70, and 160 µm to determine the 5-� confusion limits due to extragalactic sources: 56µJy, 3.2 and 40 mJy at 24, 70 and 160 µm, respectively. We also make predictions for confusion limits for a number of proposed far infrared missions of larger aperture (3.5 to 10m diameter). Subject headings: infrared: galaxies – galaxies: evolution – galaxies: statistics