Work Description

Title: Line of Sight Velocity Distributions and Photometry Data for the paper The Black Hole Mass and Photometric Components of NGC 4826 Open Access Deposited

h
Attribute Value
Methodology
  • These data are high-level data products of line-of-sight velocity distributions (LOSVDs) for the galaxy NGC 4826 (from the New General Catalog) also known as M64 (from the Messier catalog of non-cometary objects, Catalogue des Nébuleuses et des Amas d'Étoiles). Data were from Hubble Space Telescope / Space Telescope Imaging Spectrograph (HST/STIS) and Hobby-Ebberly Telescope / Low-Resolution Spectrograph (HET/LRS). The spectra were fit to extract LOSVDs from the Ca II Triplet region of the spectrum using the following method. The STIS observations of NGC 4826 were used for Ca II triplet absorption measurement. The spectrograph was operated with the G750M grating. The 52" x 0.1" slit was positioned at the center of the galaxy, aligned with the galaxy major axis as determined from ground-based images (Position Angle [PA] = 110.3 degrees). Two exposures at central wavelength 8561 Å were taken at two dither positions for a total exposure time of 4190 s, and a third exposure was taken at central wavelength 6581 Å for 2842 s. The wavelength range of the spectra targeting the Ca II absorption was 8275--8842 Å. We followed standard pipeline procedures for our STIS data reduction. First, we extracted the raw spectra from the dataset and then we subtracted a value coming from a constant fit to the overscan region for bias determination. We used an iterative self-dark technique to take into account dark current as well as the warm and hot STIS CCD (Charge-Coupled Device) pixels. Next we flat-fielded, dark-subtracted, and shifted the spectra to a common dither position to combine into a final two-dimensional spectrum. One-dimensional spectra were then extracted using a bi-weight combination of rows. The STIS stellar absorption line data only extend to about 1" before the signal to noise becomes low enough to make the data unuseful, and we require additional spectroscopic data in order to measure the mass-to-light ratio and the stellar orbital structure, both of which are important for a measure of the black hole mass. The large radial spectroscopic data come from van den Bosch et al. (2015, doi:10.1088/0067-0049/218/1/10), using the Marcario Low Resolution Spectrometer (Hill et al. 1998; doi:10.1117/12.316773) on the Hobby-Eberly Telescope (HET). The HET spectra come from two slit positions: along the major axis and along the minor axis. The reductions follow van den Bosch (2012; doi:10.1038/nature11592) and van den Bosch et al. (2015, doi:10.1088/0067-0049/218/1/10). From the one-dimensional spectrum we extracted line-of-sight velocity distributions (LOSVDs) as described in Gültekin et al. (2009; doi:10.1088/0004-637X/695/2/1577), using the stellar template library due to Gebhardt (2003; doi:10.1086/345081). We experimented with several different spatial binning schemes to find the best combination of spatial resolution and signal to noise ratio (S/N). The best combination was a range of bin sizes from 0.05--0.55". Original HST data can be downloaded from  https://doi.org/10.17909/yep1-qr33 .
Description
  • These data came from research that was geared towards measuring the mass of the black hole in the galaxy NGC 4826. The data are line-of-sight velocity distributions (LOSVDs) inferred from high-spatial resolution stellar absorption line spectra of Hubble Space Telescope / Space Telescope Imaging Spectrograph (HST/STIS) data and lower-spatial resolution stellar absorption line spectra of Hobby-Ebberly Telescope / Low-Resolution Spectrograph (HET/LRS) data. These data can be used for kinematic analysis of the galaxy NGC 4826 (M64) including black hole mass estimation. The HST/STIS data span about one arcsec, and the HET/LRS data span about 90 arcsec.
Creator
Depositor
  • kayhan@umich.edu
Contact information
Discipline
Funding agency
  • National Aeronautics and Space Administration (NASA)
Keyword
Date coverage
  • 2001-04-20 to 2001-04-21
Citations to related material
  • Gültekin et al. (2024, in press)
Resource type
Last modified
  • 09/06/2024
Published
  • 09/06/2024
Language
DOI
  • https://doi.org/10.7302/kr8z-fj98
License
To Cite this Work:
Gultekin, K., Gebhardt, K., Kormendy, J., Foord, A., Bender, R., Lauer, T. R., Pinkney, J., Richstone, D. O., Tremaine, S. (2024). Line of Sight Velocity Distributions and Photometry Data for the paper The Black Hole Mass and Photometric Components of NGC 4826 [Data set], University of Michigan - Deep Blue Data. https://doi.org/10.7302/kr8z-fj98

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Files (Count: 3; Size: 25.6 KB)

Thumbnailthumbnail-column Title Original Upload Last Modified File Size Access Actions
losvd_data.csv 2024-08-06 2024-08-06 21.4 KB Open Access
losvd_spat_bins.csv 2024-08-06 2024-08-06 1 KB Open Access
README.txt 2024-09-05 2024-09-05 3.21 KB Open Access

Date: 2024 Apr 05

Dataset Title: Line of Sight Velocity Distributions and Photometry Data for the paper The Black Hole Mass and Photometric Components of NGC 4826

Dataset Creators: Kayhan Gultekin (https://orcid.org/0000-0002-1146-0198), Karl Gebhardt (https://orcid.org/0000-0002-8433-8185), John Kormendy (https://orcid.org/0000-0001-9854-5217), Adi Foord (https://orcid.org/0000-0002-1616-1701), Ralf Bender (https://orcid.org/0000-0001-7179-0626), Tod Lauer (https://orcid.org/0000-0003-3234-7247), Jason Pinkney, Douglas O. Richstone, Scott Tremaine (https://orcid.org/0000-0002-0278-7180)

Dataset Contact: Kayhan Gultekin (kayhan@umich.edu)

This dataset contains this README, and several ascii files with data formats explained below.

losvd_data.csv:
This file contains line-of-sight velocity distributions (LOSVDs) for the galaxy NGC 4826 taken from HST/STIS and HET/LRS as explained in the associated paper. Columns of this file are:
spatial_bin_index: index indicating which spatial bin the LOSVD belongs to. Corresponds to coordinates given in losvd_spat_bins.csv. Indexing starts at 1 because the program was written in FORTRAN 77. values 1--8 correspond to HST spectra. Values 9--38 correspond to HET spectra.
velocity_bin_index: index indicating which velocity bin the line belongs to,
velocity: central velocity of the velocity bin in km/s
f: distribution function value (arbitrary units)
f_upper: The 1-sigma upper bound on f,
f_lower: The 1-sigma lower bound on f

losvd_spat_bins.csv:
This file contains coordinates and information for the spatial bins of the LOSVDs. Coordinates are given in x and y, relative to the center of the galaxy defined by the dispersion peak of the galaxy, and the major axis of the galaxy corresponds to y=0. Units of coordinates are arcsec. Spatial bins are only defined for the upper-right quadrant as symmetry is assumed. Columns of this file are:
spatial_bin_index: index indicating which spatial bin the LOSVD belongs to. LOSVD values are given in losvd_data.csv. Indexing starts at 1 because the program was written in FORTRAN 77. values 1--8 correspond to HST spectra. Values 1 and 2 correspond to bins that were taken from the negative-x side of the galaxy (West?) but have been flipped (appropriately changed in the LOSVD data as well) to the positive side for symmetry. Values 9--38 correspond to HET spectra.
x_center: x-coordinate of bin
y_center: y-coordinate of bin
instr_code: 1 = HST data, 2 = HET data
x_min: min x-coord of spatial bin (if x_max = -1 width of bin is half-way between neighboring bins)
x_max: max x-coord of spatial bin (if x_max = -1 width of bin is half-way between neighboring bins)
y_min: min y-coord of spatial bin
y_max: max y-coord of spatial bin

Use and Access:
This data set is made available under a Creative Commons BY-NC license (CC BY_NC 4.0), http://creativecommons.org/licenses/by-nc/4.0/.

To Cite Data:
Gultekin, K., Gebhardt, K., Kormendy, J., Foord, A., Bender, R., Lauer, T. R., Pinkney, J., Richstone, D. O., Tremaine, S. Line of Sight Velocity Distributions and Photometry Data for the paper The Black Hole Mass and Photometric Components of NGC 4826 [Data set], University of Michigan - Deep Blue Data. https://doi.org/10.7302/kr8z-fj9

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