Testing Accuracy and Precision of Existing Photometry Algorithms on Moving Targets

Sonnett, S.; Meech, К. J.; Jedicke, Robert; Bus, S. J.; Tonry, J.; Hainaut, Olivier

doi:10.1086/670593

Cited by 18 publications

(16 citation statements)

References 22 publications

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“…These are the photon noise within the aperture, the standard deviation of the pixels comprising the sky ring that are used to determine the background, and a term that accounts for the uncertainty in the background level. 32 Our derived error estimates were verified with and compared to the ones available in Ref. 33.…”

Section: Construction Of Polarimetric Pointssupporting

confidence: 54%

Dual-beam optical linear polarimetry from Southern skies: characterization of CasPol for high-precision polarimetry

Sosa

Essen

Andruchow

et al. 2019

J. Astron. Telesc. Instrum. Syst.

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We present a characterization of CasPol, a dual-beam polarimeter mounted at the 2.15-m Jorge Sahade Telescope, located at the Complejo Astronómico El Leoncito, Argentina. The telescope is one of the few available meter-sized optical telescopes located in the southern hemisphere hosting a polarimeter. To carry out this work, we collected photopolarimetric data along five observing campaigns, the first one during January 2014, and the remaining ones spread between August 2017 and March 2018. The data were taken through the Johnson-Cousins V , R, and I filters. Along the campaigns, we observed eight unpolarized and four polarized standard stars. Our analysis began characterizing the impact of seeing and aperture into the polarimetric measurements, defining an optimum aperture extraction and setting a clear limit for seeing conditions. Then, we used the unpolarized standard stars to characterize the level of instrumental polarization and to assess the presence of polarization dependent on the position across the charge-coupled device. Polarized standard stars were investigated to quantify the stability of the instrument with wavelength. Specifically, we find that the overall instrumental polarization of CasPol is ∼0.2% in the V , R, and I bands, with a negligible polarization dependence on the position of the stars on the detector. The stability of the half-wave plate retarder is about 0.35 deg, making CasPol comparable to already existing instruments. We also provide measurements in the three photometric bands for both the unpolarized and polarized standard stars. Finally, we show scientific results, illustrating the capabilities of CasPol for precision polarimetry of relatively faint objects.

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Section: Construction Of Polarimetric Pointssupporting

confidence: 54%

Dual-beam optical linear polarimetry from Southern skies: characterization of CasPol for high-precision polarimetry

Sosa

Essen

Andruchow

et al. 2019

J. Astron. Telesc. Instrum. Syst.

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“…Since SExtractor generally underestimates photometric errors (e.g., Sonnett et al 2013), we decided to manually set a minimum error of 0.05 magnitudes for all those detections with a photometric error less than that value. Indeed, it represents the minimum systematic error for HST imaging data.…”

Section: Hst Photometry Of the Hff Lyα Emittersmentioning

confidence: 99%

The galaxy starburst/main-sequence bimodality over five decades in stellar mass at z ~ 3-6.5

Rinaldi,

Caputi,

van Mierlo

et al. 2021

Preprint

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We study the relation between stellar mass (M * ) and star formation rate (SFR) for star-forming galaxies over approximately five decades in stellar mass (5.5 log 10 (M * /M ) 10.5) at z ≈ 3 − 6.5. This unprecedented coverage has been possible thanks to the joint analysis of blank non-lensed fields (COSMOS/SMUVS) and cluster lensing fields (Hubble Frontier Fields) which allow us to reach very low stellar masses. Previous works have revealed the existence of a clear bimodality in the SFR − M * plane with a star-formation Main Sequence and a starburst cloud at z ≈ 4 − 5. Here we show that this bimodality extends to all star-forming galaxies and is valid in the whole redshift range z ≈ 3 − 6.5. We find that starbursts constitute at least ≈ 20% of all star-forming galaxies with M * 10 9 M at these redshifts and reach a peak of 40% at z = 4−5. More importantly, 60% to 90% of the total SFR budget at these redshifts is contained in starburst galaxies, indicating that the starburst mode of star-formation is dominant at high redshifts. Almost all the low stellar-mass starbursts with log 10 (M * /M ) 8.5 have ages comparable to the typical timescales of a starburst event, suggesting that these galaxies are being caught in the process of formation. Interestingly, galaxy formation models fail to predict the starburst/main-sequence bimodality and starbursts overall, suggesting that the starburst phenomenon may be driven by physical processes occurring at smaller scales than those probed by these models.

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“…A correction is then applied to account for the flux excluded by that aperture based on a 2 dimensional Gaussian profile fit to the source. In this way, source elongation can be at least roughly accounted for, with the RMS uncertainty increasing by modest amounts -∼ 50% in the case discussed by Sonnett et al (2013a).…”

Section: Test Of the Proceduresmentioning

confidence: 97%

“…Recently, Sonnett et al (2013a) presented a comparison of the relative performances of various photometry techniques in the scenario of moderate SNR observations ( 20), of a Kuiper Belt Object, moving at 2.8 "/hr. At the expense of knowledge of the PSF and any aperture corrections, the telescope was tracked at a non-sidereal rate to produce a (nearly) untrailed image of the KBO, allowing circular apertures to be used, facilitating comparison of a wide range of photometry packages.…”

Section: Test Of the Proceduresmentioning

confidence: 99%

TRIPPy: TRAILED IMAGE PHOTOMETRY IN PYTHON

Fraser

Alexandersen

Schwamb

et al. 2016

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Photometry of moving sources typically suffers from a reduced signal-to-noise ratio (S/N) or flux measurements biased to incorrect low values through the use of circular apertures. To address this issue, we present the software package, TRIPPy: TRailed Image Photometry in Python. TRIPPy introduces the pill aperture, which is the natural extension of the circular aperture appropriate for linearly trailed sources. The pill shape is a rectangle with two semicircular end-caps and is described by three parameters, the trail length and angle, and the radius. The TRIPPy software package also includes a new technique to generate accurate model point-spread functions (PSFs) and trailed PSFs (TSFs) from stationary background sources in sidereally tracked images. The TSF is merely the convolution of the model PSF, which consists of a moffat profile, and super-sampled lookup table. From the TSF, accurate pill aperture corrections can be estimated as a function of pill radius with an accuracy of 10 mmag for highly trailed sources. Analogous to the use of small circular apertures and associated aperture corrections, small radius pill apertures can be used to preserve S/Ns of low flux sources, with appropriate aperture correction applied to provide an accurate, unbiased flux measurement at all S/Ns.

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Testing Accuracy and Precision of Existing Photometry Algorithms on Moving Targets

Cited by 18 publications

References 22 publications

Dual-beam optical linear polarimetry from Southern skies: characterization of CasPol for high-precision polarimetry

Dual-beam optical linear polarimetry from Southern skies: characterization of CasPol for high-precision polarimetry

The galaxy starburst/main-sequence bimodality over five decades in stellar mass at z ~ 3-6.5

TRIPPy: TRAILED IMAGE PHOTOMETRY IN PYTHON

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