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Galaxy

About: Galaxy is a(n) research topic. Over the lifetime, 109980 publication(s) have been published within this topic receiving 4788911 citation(s). The topic is also known as: extragalactic nebula.

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Open accessJournal ArticleDOI: 10.1086/305772
Abstract: We present a full-sky 100 μm map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 μm data, we have constructed a map of the dust temperature so that the 100 μm map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of H2 in molecular clouds. In contrast, high-velocity H I clouds are deficient in dust emission, as expected. To generate the full-sky dust maps, we must first remove zodiacal light contamination, as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 μm DIRBE map against the Leiden-Dwingeloo map of H I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 μm flux. This procedure removes virtually all traces of the zodiacal foreground. For the 100 μm map no significant CIB is detected. At longer wavelengths, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 ± 13 nW m-2 sr-1 at 140 μm and of 17 ± 4 nW m-2 sr-1 at 240 μm (95% confidence). This integrated flux ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. To calibrate our maps, we assume a standard reddening law and use the colors of elliptical galaxies to measure the reddening per unit flux density of 100 μm emission. We find consistent calibration using the B-R color distribution of a sample of the 106 brightest cluster ellipticals, as well as a sample of 384 ellipticals with B-V and Mg line strength measurements. For the latter sample, we use the correlation of intrinsic B-V versus Mg2 index to tighten the power of the test greatly. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening. The maps are expected to be significantly more accurate in regions of high reddening. These dust maps will also be useful for estimating millimeter emission that contaminates cosmic microwave background radiation experiments and for estimating soft X-ray absorption. We describe how to access our maps readily for general use.

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Topics: Spinning dust (62%), Zodiacal light (57%), Cosmic infrared background (56%) ...read more

15,382 Citations


Open accessJournal ArticleDOI: 10.1088/0067-0049/182/2/543
Abstract: This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg^2 of imaging data, with most of the ~2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120° long, 2°.5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg^2. The survey has completed spectroscopy over 9380 deg^2; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.

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  • Table 1 Coverage and Contents of DR7
    Table 1 Coverage and Contents of DR7
  • Figure 1. Distribution on the sky of the data included in DR7 (upper panel: imaging; lower panel: spectra), shown in an Aitoff equal-area projection in J2000 Equatorial Coordinates. The Galactic plane is the sinuous line that goes through each panel. The center of each panel is at α = 120◦ ≡ 8h, and the plots cut off at δ = −25◦, below which the SDSS did not extend. The Legacy imaging survey covers the contiguous area of the Northern Galactic Cap (centered roughly at α = 200◦, δ = 30◦), as well as three stripes (each of width 2.◦5) in the Southern Galactic Cap. In addition, several stripes (indicated in blue in the imaging data) are auxiliary imaging data, while the SEGUE imaging scans are indicated in red. The green scans are additional runs as described in Finkbeiner et al. (2004). In the spectroscopy panel, the lighter regions indicate that area in the Northern Galactic Cap which is new to DR7; note that the Northern Galactic Cap is now contiguous. Red points indicate SEGUE plates and blue points indicate other non-Legacy plates (mostly as described in the DR4 paper).
    Figure 1. Distribution on the sky of the data included in DR7 (upper panel: imaging; lower panel: spectra), shown in an Aitoff equal-area projection in J2000 Equatorial Coordinates. The Galactic plane is the sinuous line that goes through each panel. The center of each panel is at α = 120◦ ≡ 8h, and the plots cut off at δ = −25◦, below which the SDSS did not extend. The Legacy imaging survey covers the contiguous area of the Northern Galactic Cap (centered roughly at α = 200◦, δ = 30◦), as well as three stripes (each of width 2.◦5) in the Southern Galactic Cap. In addition, several stripes (indicated in blue in the imaging data) are auxiliary imaging data, while the SEGUE imaging scans are indicated in red. The green scans are additional runs as described in Finkbeiner et al. (2004). In the spectroscopy panel, the lighter regions indicate that area in the Northern Galactic Cap which is new to DR7; note that the Northern Galactic Cap is now contiguous. Red points indicate SEGUE plates and blue points indicate other non-Legacy plates (mostly as described in the DR4 paper).
  • Figure 2. Distribution on the sky of SEGUE (red) and other non-Legacy (blue) spectroscopic observations, here plotted in Galactic coordinates. The contiguous blue stripe across the bottom is Stripe 82, along the celestial equator. As described in the DR4 paper, Stripe 82 includes extensive spectroscopy of a number of different types of targets outside the Legacy Survey.
    Figure 2. Distribution on the sky of SEGUE (red) and other non-Legacy (blue) spectroscopic observations, here plotted in Galactic coordinates. The contiguous blue stripe across the bottom is Stripe 82, along the celestial equator. As described in the DR4 paper, Stripe 82 includes extensive spectroscopy of a number of different types of targets outside the Legacy Survey.
  • Figure 3. Stripe 82, the equatorial stripe in the South Galactic Cap, has been imaged multiple times. The lower pair of curves shows the number of scans covering a given right ascension in the North and South strips that are included in the co-addition (mostly data taken through 2005). In addition, Stripe 82 has been covered many more times as part of a comprehensive survey for 0.05 < z < 0.35 supernovae, although often in conditions of poor seeing, bright moon, and/or clouds; the total numbers of scans at each right ascension in the North and South strips are indicated in the upper pair of curves. All these data have been flux calibrated, as discussed in the text, and are available (together with the co-add itself) in the stripe82 database.
    Figure 3. Stripe 82, the equatorial stripe in the South Galactic Cap, has been imaged multiple times. The lower pair of curves shows the number of scans covering a given right ascension in the North and South strips that are included in the co-addition (mostly data taken through 2005). In addition, Stripe 82 has been covered many more times as part of a comprehensive survey for 0.05 < z < 0.35 supernovae, although often in conditions of poor seeing, bright moon, and/or clouds; the total numbers of scans at each right ascension in the North and South strips are indicated in the upper pair of curves. All these data have been flux calibrated, as discussed in the text, and are available (together with the co-add itself) in the stripe82 database.
  • Table 2 Asinh Magnitude Softening Parameters for the Co-Addition
    Table 2 Asinh Magnitude Softening Parameters for the Co-Addition
  • + 7

Topics: Photometry (astronomy) (54%), Astrograph (53%), Galaxy (52%) ...read more

5,374 Citations


Open accessJournal ArticleDOI: 10.1088/0067-0049/182/2/543
Abstract: This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most of the roughly 2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry over 250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A coaddition of these data goes roughly two magnitudes fainter than the main survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2 in the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog (UCAC-2), reducing the rms statistical errors at the bright end to 45 milli-arcseconds per coordinate. A systematic error in bright galaxy photometr is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat-fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities. (Abridged)

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  • Table 1 Coverage and Contents of DR7
    Table 1 Coverage and Contents of DR7
  • Figure 1. Distribution on the sky of the data included in DR7 (upper panel: imaging; lower panel: spectra), shown in an Aitoff equal-area projection in J2000 Equatorial Coordinates. The Galactic plane is the sinuous line that goes through each panel. The center of each panel is at α = 120◦ ≡ 8h, and the plots cut off at δ = −25◦, below which the SDSS did not extend. The Legacy imaging survey covers the contiguous area of the Northern Galactic Cap (centered roughly at α = 200◦, δ = 30◦), as well as three stripes (each of width 2.◦5) in the Southern Galactic Cap. In addition, several stripes (indicated in blue in the imaging data) are auxiliary imaging data, while the SEGUE imaging scans are indicated in red. The green scans are additional runs as described in Finkbeiner et al. (2004). In the spectroscopy panel, the lighter regions indicate that area in the Northern Galactic Cap which is new to DR7; note that the Northern Galactic Cap is now contiguous. Red points indicate SEGUE plates and blue points indicate other non-Legacy plates (mostly as described in the DR4 paper).
    Figure 1. Distribution on the sky of the data included in DR7 (upper panel: imaging; lower panel: spectra), shown in an Aitoff equal-area projection in J2000 Equatorial Coordinates. The Galactic plane is the sinuous line that goes through each panel. The center of each panel is at α = 120◦ ≡ 8h, and the plots cut off at δ = −25◦, below which the SDSS did not extend. The Legacy imaging survey covers the contiguous area of the Northern Galactic Cap (centered roughly at α = 200◦, δ = 30◦), as well as three stripes (each of width 2.◦5) in the Southern Galactic Cap. In addition, several stripes (indicated in blue in the imaging data) are auxiliary imaging data, while the SEGUE imaging scans are indicated in red. The green scans are additional runs as described in Finkbeiner et al. (2004). In the spectroscopy panel, the lighter regions indicate that area in the Northern Galactic Cap which is new to DR7; note that the Northern Galactic Cap is now contiguous. Red points indicate SEGUE plates and blue points indicate other non-Legacy plates (mostly as described in the DR4 paper).
  • Figure 2. Distribution on the sky of SEGUE (red) and other non-Legacy (blue) spectroscopic observations, here plotted in Galactic coordinates. The contiguous blue stripe across the bottom is Stripe 82, along the celestial equator. As described in the DR4 paper, Stripe 82 includes extensive spectroscopy of a number of different types of targets outside the Legacy Survey.
    Figure 2. Distribution on the sky of SEGUE (red) and other non-Legacy (blue) spectroscopic observations, here plotted in Galactic coordinates. The contiguous blue stripe across the bottom is Stripe 82, along the celestial equator. As described in the DR4 paper, Stripe 82 includes extensive spectroscopy of a number of different types of targets outside the Legacy Survey.
  • Figure 3. Stripe 82, the equatorial stripe in the South Galactic Cap, has been imaged multiple times. The lower pair of curves shows the number of scans covering a given right ascension in the North and South strips that are included in the co-addition (mostly data taken through 2005). In addition, Stripe 82 has been covered many more times as part of a comprehensive survey for 0.05 < z < 0.35 supernovae, although often in conditions of poor seeing, bright moon, and/or clouds; the total numbers of scans at each right ascension in the North and South strips are indicated in the upper pair of curves. All these data have been flux calibrated, as discussed in the text, and are available (together with the co-add itself) in the stripe82 database.
    Figure 3. Stripe 82, the equatorial stripe in the South Galactic Cap, has been imaged multiple times. The lower pair of curves shows the number of scans covering a given right ascension in the North and South strips that are included in the co-addition (mostly data taken through 2005). In addition, Stripe 82 has been covered many more times as part of a comprehensive survey for 0.05 < z < 0.35 supernovae, although often in conditions of poor seeing, bright moon, and/or clouds; the total numbers of scans at each right ascension in the North and South strips are indicated in the upper pair of curves. All these data have been flux calibrated, as discussed in the text, and are available (together with the co-add itself) in the stripe82 database.
  • Table 2 Asinh Magnitude Softening Parameters for the Co-Addition
    Table 2 Asinh Magnitude Softening Parameters for the Co-Addition
  • + 7

Topics: Galaxy (53%), Celestial equator (53%), Astrograph (52%) ...read more

4,909 Citations


Open accessJournal ArticleDOI: 10.1086/308692
Daniela Calzetti1, Lee Armus2, Ralph C. Bohlin1, Anne L. Kinney1  +2 moreInstitutions (4)
Abstract: We present far-infrared (FIR) photometry at 150 and 205 micron(s) of eight low-redshift starburst galaxies obtained with the Infrared Space Observatory (ISO) ISOPHOT. Five of the eight galaxies are detected in both wave bands, and these data are used, in conjunction with IRAS archival photometry, to model the dust emission at lambda approximately greater than 40 microns. The FIR spectral energy distributions (SEDs) are best fitted by a combination of two modified Planck functions, with T approx. 40 - 55 K (warm dust) and T approx. 20-23 K (cool dust) and with a dust emissivity index epsilon = 2. The cool dust can be a major contributor to the FIR emission of starburst galaxies, representing up to 60% of the total flux. This component is heated not only by the general interstellar radiation field, but also by the starburst itself. The cool dust mass is up to approx. 150 times larger than the warm dust mass, bringing the gas-to-dust ratios of the starbursts in our sample close to Milky Way values, once resealed for the appropriate metallicity. The ratio between the total dust FIR emission in the range 1-1000 microns and the IRAS FIR emission in the range 40 - 120 microns is approx. 1.75, with small variations from galaxy to galaxy. This ratio is about 40% larger than previously inferred from data at millimeter wavelengths. Although the galaxies in our sample are generally classified as "UV bright," for four of them the UV energy emerging shortward of 0.2 microns is less than 15% of the FIR energy. On average, about 30% of the bolometric flux is coming out in the UV-to-near-IR wavelength range; the rest is emitted in the FIR. Energy balance calculations show that the FIR emission predicted by the dust reddening of the UV-to-near-IR stellar emission is within a factor of approx. 2 of the observed value in individual galaxies and within 20% when averaged over a large sample. If our sample of local starbursts is representative of high-redshift (z approx. greater than 1), UV - bright star-forming galaxies, these galaxies' FIR emission will be generally undetected in submillimeter surveys, unless: (1) their bolometric luminosity is comparable to or larger than that of ultraluminous FIR galaxies and (2) their FIR SED contains a cool dust component.

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  • TABLE 1
    TABLE 1
  • TABLE 2
    TABLE 2
  • FIG. 1.ÈSpectral energy distributions, from 0.12 to 240 km, of the eight galaxies in our sample. UV-optical spectrophotometry is shown as a continuous line in the wavelength range 0.12È1.0 km, near-IR photometry as empty circles, IRAS data as Ðlled squares, and our ISO measurements as Ðlled triangles. Upper limits are shown as downward arrows. No renormalization between the small UVÈopticalÈnear-IR observational apertures (D20@@] 10@@) and the large FIR apertures (D a few arcminutes) has been performed. For Ðve of the galaxies, the best-Ðt curve to the dust emission in the range 40È240 km is also shown (solid line). The best-Ðt model corresponds to single or two modiÐed Planck functions with the temperatures given in Table 3, a dust emissivity v\ 2, and 50% contribution to the observed F(25) Ñux density. For comparison, a model of a single blackbody with v\ 1 dust emissivity is also shown (dashed line).
    FIG. 1.ÈSpectral energy distributions, from 0.12 to 240 km, of the eight galaxies in our sample. UV-optical spectrophotometry is shown as a continuous line in the wavelength range 0.12È1.0 km, near-IR photometry as empty circles, IRAS data as Ðlled squares, and our ISO measurements as Ðlled triangles. Upper limits are shown as downward arrows. No renormalization between the small UVÈopticalÈnear-IR observational apertures (D20@@] 10@@) and the large FIR apertures (D a few arcminutes) has been performed. For Ðve of the galaxies, the best-Ðt curve to the dust emission in the range 40È240 km is also shown (solid line). The best-Ðt model corresponds to single or two modiÐed Planck functions with the temperatures given in Table 3, a dust emissivity v\ 2, and 50% contribution to the observed F(25) Ñux density. For comparison, a model of a single blackbody with v\ 1 dust emissivity is also shown (dashed line).
  • TABLE 3
    TABLE 3
  • TABLE 4
    TABLE 4
  • + 7

Topics: Luminous infrared galaxy (63%), Galaxy (56%), Lyman-break galaxy (54%) ...read more

4,719 Citations


Book ChapterDOI: 10.1007/978-1-4757-4363-0_1
01 Jan 1991-
Abstract: This new, enlarged reference catalogue of bright galaxies in three volumes reflects the explosive growth of extragalactic astronomy over the last 15 years. With data on more than 23,000 galaxies, it includes all galaxies with apparent diameters larger than one arc minute, magnitudes brighter than about magnitude 15.5, and redshifts not larger than 15,000 km/sec, as well as many other objects of interest. Volume 1 contains the explanations and references; volumes 2 and 3 contain the catalogue proper. The catalogue gives for each galaxy, the position, names, type and luminosity class, optical diameters, optical and infrared magnitudes, various colour indices and radial velocities. The work also makes reference to papers on bright galaxies published between 1913 and 1988. This dictionary/encyclopaedia on stellar systems is intended for researchers in astronomy.

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Topics: Luminous infrared galaxy (61%), Dwarf elliptical galaxy (57%), Extragalactic astronomy (57%) ...read more

4,561 Citations


Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20222
20213,364
20204,053
20194,376
20184,082
20173,893

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Topic's top 5 most impactful authors

Francoise Combes

712 papers, 26.2K citations

Anton M. Koekemoer

665 papers, 65K citations

Rob Ivison

657 papers, 63K citations

Luis C. Ho

578 papers, 41.8K citations

Fabian Walter

515 papers, 44.9K citations

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