J/AJ/154/53 WISE/NEOWISE observations of comets (Bauer+, 2017)
Debiasing the NEOWISE cryogenic mission comet populations. Bauer J.M., Grav T., Fernandez Y.R., Mainzer A.K., Kramer E.A., Masiero J.R., Spahr T., Nugent C.R., Stevenson R.A., Meech K.J., Cutri R.M., Lisse C.M., Walker R., Dailey J.W., Rosser J., Krings P., Ruecker K., Wright E.L., (the NEOWISE Team) <Astron. J., 154, 53-53 (2017)> =2017AJ....154...53B (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Comets ; Infrared sources ; Surveys Keywords: comets: general - infrared: planetary systems - Oort Cloud - surveys Abstract: We use NEOWISE data from the four-band and three-band cryogenic phases of the Wide-field Infrared Survey Explorer mission to constrain size distributions of the comet populations and debias measurements of the short- and long-period comet (LPC) populations. We find that the fit to the debiased LPC population yields a cumulative size-frequency distribution (SFD) power-law slope (β) of -1.0±0.1, while the debiased Jupiter-family comet (JFC) SFD has a steeper slope with β=-2.3±0.2. The JFCs in our debiased sample yielded a mean nucleus size of 1.3km in diameter, while the LPCs' mean size is roughly twice as large, 2.1km, yielding mean size ratios (<DLPC>/<DJFC>) that differ by a factor of 1.6. Over the course of the 8 months of the survey, our results indicate that the number of LPCs passing within 1.5 au are a factor of several higher than previous estimates, while JFCs are within the previous range of estimates of a few thousand down to sizes near 1.3km in diameter. Finally, we also observe evidence for structure in the orbital distribution of LPCs, with an overdensity of comets clustered near 110° inclination and perihelion near 2.9 au that is not attributable to observational bias. Description: NEOWISE/WISE detected 164 recognized cometary bodies during the four-band mission, including 56 Long-Period Comets (LPCs) and 108 Short-Period Comets (SPCs). A total of 71 of these were detected by creating stacked images in the co-moving reference frames of previously known comets that were undetectable in the individual frames. Objects recovered from stacked images will be affected by different detection biases (e.g., they were found at different sensitivity levels) than those detected by the WISE Moving Object Processing System (WMOPS) and so are excluded from the debiasing analyses. A total of 95 of the 108 SPCs were Jupiter-Family Comets (JFCs), the remainder being 7 active main-belt asteroids, 4 active centaurs, and 2 Halley-type comets. Several comets have been discussed in previous publications. NEOWISE observations of those comets not discussed in previous publications and their extracted fluxes from the stacked images are summarized in Table1. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 72 107 Comet observations table2.dat 94 10 Coma subtraction model fit parameters table3.dat 165 188 Diameters and εfρ
See also: B/comets : Database of the orbital elements of comets (Rocher, 2007) II/311 : WISE All-Sky Data Release (Cutri+ 2012) J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014) J/ApJ/760/L12 : WISE/NEOWISE NEOs preliminary thermal fits (Mainzer+, 2012) J/ApJ/759/L8 : Main belt asteroids WISE/NEOWISE observations (Masiero+, 2012) J/ApJ/759/49 : WISE/NEOWISE Jovian Trojan asteroids: taxonomy (Grav+, 2012) J/ApJ/744/197 : WISE/NEOWISE observations of Hilda asteroids (Grav+, 2012) J/ApJ/743/156 : NEOWISE obs. of NEOs: preliminary results (Mainzer+, 2011) J/ApJ/742/40 : Jovian Trojans asteroids with WISE/NEOWISE (Grav+, 2011) J/ApJ/741/68 : Main Belt asteroids with WISE/NEOWISE. I. (Masiero+, 2011) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 5 A5 --- Type Period type (Short or Long) 7- 17 A11 --- Comet Comet designation 19- 23 F5.2 AU Rhelio [2/12] Heliocentric distance 25- 29 F5.2 AU Delta [1.73/11.85] Comet-spacecraft distance Δ 31- 36 F6.2 mJy SW3 [0.05/410]? WISE W3 band (12µm) band flux density (1) 38- 42 F5.2 mJy e_SW3 [0.02/75]? Uncertainty in SW3 44- 49 F6.2 mJy SW4 [1.5/127]? WISE W4 band (22µm) band flux density (1) 51- 55 F5.2 mJy e_SW4 [0.5/24]? Uncertainty in SW4 57 A1 --- Act Apparent activity? (Y=Yes, N=No, U=Uncertain) (2) 59- 69 F11.5 d MJD Modified Julian Date of stacked image mid-exposure 71- 72 I2 --- Nfr [3/38] Number of frames co-added in stacked image
Note (1): From 11'' aperture. Conversion from DNs to flux were carried out as described in Wright et al. (2010AJ....140.1868W). A blank indicates extracted flux values with no detectable signal. Note (2): Apparent activity flags are defined as follows: Y = Apparent activity in the image (dust coma or tail). There's obvious coma; N = No apparent sign of activity (no obvious coma); U = Coma presence could not be ruled out.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 A2 --- Band WISE band 4 I1 --- Model Model 6- 8 F3.1 arcsec Int0 ? Starting value of the coma fit interval (1) 9 A1 --- --- [-] 10- 13 F4.1 arcsec Int1 ? Ending value of the coma fit interval (1) 15- 49 A35 --- n_Int1 Note about the coma fit interval 51- 94 A44 --- Com Comments
Note (1): Coma fit interval in arcsec from central condensation.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 5 A5 --- Type Period type (Short or Long) 7- 17 A11 --- Comet Comet designation 19 A1 --- f_Comet [*] Flag on Comet (1) 21- 24 F4.2 --- eta [0.56/1.6]? Dimensionless beaming parameter η (2) 26- 29 F4.2 --- e_eta [0.02/0.85]? Uncertainty in eta 31- 36 F6.2 km Diam [0.43/201]? Diameter 38- 42 F5.2 km e_Diam [0.04/62]? Uncertainty in Diam 44 A1 --- l_efrho [<] Upper limit flag on efrho 45- 49 F5.2 [cm] efrho [0/30]? Log emissivity-fractional area-comet centric distance εfρ (3) 51- 54 F4.2 [cm] e_efrho [0/5]? Uncertainty in εfρ 56 I1 --- W3a [1/5]? Coma subtraction model for W3 band (4) 58 I1 --- W3b [2/4]? Coma subtraction model for W3 band (4) 60 I1 --- W3c [3/4]? Coma subtraction model for W3 band (4) 62 I1 --- W3d ? Coma subtraction model for W3 band (4) 64- 95 A32 --- r_W3d Reference where diameter fits were previously published 97 I1 --- W4a [1/5]? Coma subtraction model for W4 band (4) 99 I1 --- W4b [2/4]? Coma subtraction model for W4 band (4) 101 I1 --- W4c [3/4]? Coma subtraction model for W4 band (4) 103 I1 --- W4d ? Coma subtraction model for W4 band (4) 105-136 A32 --- r_W4d Reference where diameter fits were previously published 138-165 A28 --- Com Additional comments regarding fits and signal
Note (1): * = The comet was NOT detected by the WISE Moving Object Processing System (WMOPS), but was rather found in the co-moving image stacks. Note (2): Provided for those fits where η was a free parameter. A blank value indicates η was fixed (see text). Note (3): A blank indicates the signal was too weak to constrain εfρ. Values of 0 for εfρ indicate no evidence of coma. Note (4): The coma subtraction models for W3 and W4 that were used for the nucleus effective diameter fits, as listed in Table2 and described in the text. Blank values in these two columns indicate that the signal in that band was not used in the diameter fit, usually owing to the weak signal in that band.
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 25-Oct-2017
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