Spirality: A Novel Way to Measure Spiral Arm Pitch Angle

Shields, Douglas W.; Boe, Benjamin; Pfountz, Casey; Davis, Benjamin L.; Hartley, Matthew; Imani, Hamed Pour; Slade, Zac; Kennefick, Daniel; Kennefick, Julia

doi:10.48550/arxiv.1511.06365

Cited by 8 publications

(13 citation statements)

References 17 publications

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“…A large fraction of local spirals can be modeled by superpositions of logarithmic spiral functions. Based on this, automatic spiral arm finding and logarithmic function fitting tools have been developed and applied in local galaxy surveys (e.g., Davis et al 2012;Davis & Hayes 2014;Shields et al 2015;Hart et al 2017). Our on-going effort of testing and adapting these tools at high-redshift will help to quantify spiral arms and to separate spiral from irregular structures objectively.…”

Section: Spiral Arms Vs Clumpy Disks and Irregularsmentioning

confidence: 99%

“…Most galaxies at z 2 have half-light radii of ≤ 0. ′′ 3 (Allen et al 2016), making the identification and quantification of spiral features such as the number of arms and pitch angles challenging (Shields et al 2015). More studies like van den Bergh et al (2002) focusing on testing the visibility of spiral arms at high redshift are required before concluding the actual number density of spiral galaxies at z > 1.…”

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confidence: 99%

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The Most Ancient Spiral Galaxy: A 2.6-Gyr-old Disk with a Tranquil Velocity Field

Yuan

Richard

Gupta

et al. 2017

ApJ

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We report an integral-field spectroscopic (IFS) observation of a gravitationally lensed spiral galaxy A1689B11 at redshift z = 2.54. It is the most ancient spiral galaxy discovered to date and the second kinematically confirmed spiral at z 2. Thanks to gravitational lensing, this is also by far the deepest IFS observation with the highest spatial resolution (∼ 400 pc) on a spiral galaxy at a cosmic time when the Hubble sequence is about to emerge. After correcting for a lensing magnification of 7.2 ± 0.8, this primitive spiral disk has an intrinsic star formation rate of 22 ± 2 M ⊙ yr −1 , a stellar mass of 10 9.8±0.3 M ⊙ and a half-light radius of r 1/2 = 2.6 ± 0.7 kpc, typical of a main-sequence star-forming (SF) galaxy at z ∼ 2. However, the Hα kinematics show a surprisingly tranquil velocity field with an ordered rotation (V c = 200 ± 12 km s −1 ) and uniformly small velocity dispersions (V σ,mean = 23 ± 4 km s −1 and V σ,outer−disk = 15 ± 2 km s −1 ). The low gas velocity dispersion is similar to local spiral galaxies and is consistent with the classic density wave theory where spiral arms form in dynamically cold and thin disks. We speculate that A1689B11 belongs to a population of rare spiral galaxies at z 2 that mark the formation epoch of thin disks. Future observations with JWST will greatly increase the sample of these rare galaxies and unveil the earliest onset of spiral arms.

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Section: Spiral Arms Vs Clumpy Disks and Irregularsmentioning

confidence: 99%

mentioning

confidence: 99%

The Most Ancient Spiral Galaxy: A 2.6-Gyr-old Disk with a Tranquil Velocity Field

Yuan

Richard

Gupta

et al. 2017

ApJ

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“…The final determination of PA is therefore −15.07 ± 2.23. We also checked our measurement with the Spirality code of Shields et al (2015), which uses template fitting rather than Fourier decomposition to measure PA. The re-sults from these two independent methods agree well within the uncertainties.…”

Section: Spiral Arms Analysismentioning

confidence: 99%

Searching for intermediate-mass black holes in galaxies with low-luminosity AGN: a multiple-method approach

Koliopanos

Ciambur

Graham

et al. 2017

A&A

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Aims. This work is the first stage of a campaign to search for intermediate-mass black holes (IMBHs) in low-luminosity active galactic nuclei (LLAGN) and dwarf galaxies. An additional and equally important aim of this pilot study is to investigate the consistency between the predictions of several popular black hole scaling relations and the fundamental plane (FP) of black-hole activity (FP-BH). Methods. We used well established X-ray and radio luminosity relations in accreting black holes, along with the latest scaling relations between the mass of the central black hole (M BH ) and the properties of its host spheroid, to predict M BH in seven LLAGN, that were previously reported to be in the IMBH regime. Namely, we used the recently re-evaluated M BH − M sph (M sph : spheroid absolute magnitude at 3.6 µm) scaling relation for spiral galaxies, the M BH − n sph (n sph : major axis Sérsic index of the spheroid component) relation, the M BH − PA (PA: spiral pitch angle) relation, and a recently re-calibrated version of the FP-BH for weakly accreting BHs, to independently estimate M BH in all seven galaxies. Results. We find that all LLAGN in our list have low-mass central black holes with log M BH /M ≈ 6.5 on average, but that they are, most likely, not IMBHs. All four methods used predicted consistent BH masses in the 1σ range. Furthermore, we report that, in contrast to previous classification, galaxy NGC 4470 is bulge-less, and we also cast doubts on the AGN classification of NGC 3507. Conclusions. We find that our latest, state-of-the-art techniques for bulge magnitude & Sérsic index computations and the most recent updates of the M BH − L sph , M BH − n sph , and M BH − PA relations and the FP-BH produce consistent results in the low-mass regime. We thus establish a multiple-method approach for predicting BH masses in the regime where their spheres of gravitational influence cannot be spatially resolved. Our approach mitigates against outliers from any one relation and provides a more robust average prediction. We will use our new method to revisit more IMBH candidates in LLAGN.

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“…The pitch angle of a spiral is defined as the angle between the spiral's tangent at a given point and the tangent line drawn to a concentric circle with the center located at the galactic center, that passes through that point. Pitch angle measurements were performed by two independent methods namely 2DFFT method (Seigar et al 2008;Davis et al 2012) and the Spirality (Shields et al 2015) 3 method. The 2DFFT method uses a modified two dimensional fast Fourier transform process to generate the pitch angles as a function of galaxy radius in pixels for different harmonic modes.…”

Section: De-projecting and Measuring Pitch Anglesmentioning

confidence: 99%

“…This process was done by two independent methods. One using the above mentioned OL script and the other utilizing, Spirality; Spiral arm count (Shields et al 2015) script. In order to incorporate the uncertainties of the pitch angles each image was traced twice, using the maximum and the minimum pitch angle uncertainties, giving rise to two image arrays.…”

Section: Tracing the Individual Imagesmentioning

confidence: 99%

Determining the Co-Rotation Radii of Spiral Galaxies Using Spiral Arm Pitch Angle Measurements at Multiple Wavelengths

Abdeen,

Kennefick,

Kennefick

et al. 2020

Preprint

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The spiral arms spanning disk galaxies are believed to be created by density waves that propagate through galactic disks. We present a novel method of finding the co-rotation radius where the spiral arm pattern speed matches the velocities of the stars within the disk. Our method uses an imageoverlay technique, which involves tracing the arms of spiral galaxies on images observed in different wavelengths. Density wave theory predicts that spiral arms observed from different wavelengths show a phase crossing at the co-rotation radius. For the purpose of this study, 20 nearby galaxies were analyzed in four different wavelengths with pitch angle measurements performed by two independent methods. We used optical wavelength images (B-band 440nm), two infrared wavelength images provided by Spitzer (3.6µm and 8µm) and ultraviolet images from GALEX (1350 Å, 1750 Å). The results were compared and verified with other records found in the literature. We then found rotation curve data for six of our galaxies and used our co-rotation radii estimates to measure the time that would elapse between star formation and moving to their observed positions in the B-band spirals. The average time lapse for this motion was found to be ∼ 50 Myr. The success of this new method of finding the co-rotation radius confirms density wave theory in a very direct way.

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Spirality: A Novel Way to Measure Spiral Arm Pitch Angle

Cited by 8 publications

References 17 publications

The Most Ancient Spiral Galaxy: A 2.6-Gyr-old Disk with a Tranquil Velocity Field

The Most Ancient Spiral Galaxy: A 2.6-Gyr-old Disk with a Tranquil Velocity Field

Searching for intermediate-mass black holes in galaxies with low-luminosity AGN: a multiple-method approach

Determining the Co-Rotation Radii of Spiral Galaxies Using Spiral Arm Pitch Angle Measurements at Multiple Wavelengths

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