J/ApJ/853/114 Vertical population gradients in NGC 891. I. (Eigenbrot+, 2018) ================================================================================ Vertical population gradients in NGC 891. I. {nabla}Pak instrumentation and spectral data. Eigenbrot A., Bershady M.A. =2018ApJ...853..114E ================================================================================ ADC_Keywords: Galaxies, spectra; Spectroscopy; Spectra, optical Keywords: galaxies: individual (NGC 891); galaxies: spiral; galaxies: stellar content; instrumentation: spectrographs Abstract: We have measured vertical and radial stellar population gradients in NGC 891. We compare these gradients to those known for the Milky Way from studies of resolved stars. Optical spectroscopic measurements extend spatially from the disk midplane up to 2.6kpc in height and out to a radius of 12kpc on both sides of the galaxy. Data were acquired with {nabla}Pak, a variable-pitch fiber integral field unit (IFU) on the WIYN telescope. We describe the laboratory and on-sky performance of {nabla}Pak, as well as modifications to the standard observational and analysis procedures necessary to calibrate data taken with this unique IFU. {nabla}Pak has a mean throughput of 80% at 5500{AA}. To achieve an estimated precision of 10% in light-weighted mean age and metallicity, we define a set of spatial apertures in radius and height in which spectra are binned to achieve a signal-to-noise ratio of ~20{AA}^-1^. We use spectral indices to measure age, metallicity, and abundance, indicating that NGC 891's stellar populations have 0.27Gyr) stellar populations at 0.4kpc, roughly the scale height of the thin disk. We also find a slight trend toward younger populations at larger radii, consistent with flaring in an inside-out disk formation scenario. The vertical age gradient in NGC 891 is in remarkable qualitative agreement with a model for disk heating tuned to studies of the Milk Way's solar cylinder. Description: Observations of NGC 891 were obtained over two runs in 2014 November and December using the {nabla}Pak (GradPak) IFU coupled to the WIYN Bench Spectrograph. See section 4. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 02 22 32.91 +42 20 53.9 NGC 891 = LEDA 9031 ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table5.dat 74 261 Data apertures table6.dat 54 261 Velocity and radial data table8.dat 64 261 NGC 891 index measurements table9.dat 47 109 {nabla} Pak fiber locations and lab data -------------------------------------------------------------------------------- See also: III/211 : Keck/HIRES Sky Line Atlas (Osterbrock+ 1997) III/232 : STELIB: library of R~2000 stellar spectra (Le Borgne+, 2003) J/ApJS/111/377 : H{gamma} & H{delta} absorption features (Worthey+ 1997) J/MNRAS/371/703 : MILES library of empirical spectra (Sanchez-Blazquez+, 2006) J/ApJ/653/1027 : TKRS/GOODS-N Field galaxies (Weiner+, 2006) J/MNRAS/386/715 : Absorption-line strengths in Coma galaxies (Trager+, 2008) J/MNRAS/396/1231 : Astrophotometric catalogue of NGC 891 (Rejkuba+, 2009) J/ApJ/706/1364 : SINS survey of high-z galaxies (Forster Schreiber+, 2009) J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009) J/A+A/565/A4 : NGC 891 70-500um images (Hughes+, 2014) J/A+A/575/A17 : NGC 891 Herschel PACS and SPIRE spectroscopy (Hughes+, 2015) J/A+A/581/A103 : CALIFA survey across the Hubble sequence (Gonzalez+, 2015) J/ApJS/219/15 : Morphologies of z=0-10 galaxies with HST (Shibuya+, 2015) J/ApJ/832/118 : Emission-line spectroscopy in NGC 891 (Boettcher+, 2016) J/ApJ/823/114 : The Cannon: a new approach to determine masses (Ness+, 2016) Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 I1 --- P [1/6] Pointing 3- 4 I2 --- Ap [1/60] Aperture 6- 8 I3 um Core [200/600] Fiber core diameter 10- 11 I2 --- N [1/15] Number of individual fibers in aperture 13- 52 A40 --- Fiber Fiber ID's in aperture; comma-separated 54- 59 F6.2 --- SNR [13.7/108] Signal-to-noise 61- 66 F6.2 kpc rproj [-11/9] Projected radius 68- 72 F5.2 kpc Z [-0.3/2.4] Height above midplane 74 A1 --- Flag Quality flag (g=high-quality spectra) (1) -------------------------------------------------------------------------------- Note (1): Quality flag as follows: g = high-quality spectra; b = wavelength solution appears to be wrong by more than ~100km/s; u = spectra have noise structure despite acceptable signal/noise. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table6.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 I1 --- P [1/6] Pointing 3- 4 I2 --- Ap [1/60] Aperture 6- 11 F6.1 km/s VHaNS [-960/1316]?=-99 Nebular emission velocity 13- 18 F6.1 km/s e_VHaNS [24/315]?=-99 Uncertainty in VHaNS 20- 25 F6.1 km/s V*c [129/1393] Corrected stellar velocity 27- 32 F6.1 km/s VLOS [-416/1354] "Observed" line-of-sight velocity 34- 39 F6.1 km/s e_VLOS [24.5/554] Uncertainty in VLOS 41- 46 F6.1 kpc r [0.3/112] Galactic radius 48- 54 F7.1 kpc e_r [0.1/2449] Uncertainty in r -------------------------------------------------------------------------------- Byte-by-byte Description of file: table8.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 I1 --- P [1/6] Pointing 3- 4 I2 --- Ap [1/60] Aperture 6- 10 F5.2 --- Dn4000 [0.9/2.4] The 4000 Angstrom break 12- 16 F5.2 --- e_Dn4000 [0.01/0.1] Uncertainty in Dn4000 18- 22 F5.2 0.1nm HdA [-2.1/8] The H-delta index; Angstroms 24- 28 F5.2 0.1nm e_HdA [0.2/2.6] Uncertainty in HdA 30- 34 F5.2 0.1nm Mgb [0.03/4.3] The Mgb index; Angstroms 36- 40 F5.2 0.1nm e_Mgb [0.1/1.1] Uncerainty in Mgb 42- 46 F5.2 0.1nm [-0.3/2.7] Composite Iron index; Angstroms 48- 52 F5.2 0.1nm e_ [0.1/0.9] Uncertainty in 54- 58 F5.2 0.1nm [MgFe] [0.2/2.8]? The Magnesium/Iron index; Angstroms 60- 64 F5.2 0.1nm e_[MgFe] [0.1/1.8]? Uncertainty in [MgFe] -------------------------------------------------------------------------------- Byte-by-byte Description of file: table9.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- Fiber [1/109] Fiber number 5- 10 F6.2 arcsec oRA [-33.1/66.5] Offset distance in RA from fiber 105 12- 17 F6.2 arcsec oDE [-51.5/50] Offset distance in DEC from fiber 105 19- 22 F4.2 arcsec Diam [1.8/5.7] Fiber on-sky diameter 24- 27 F4.2 --- Ttot [0.7/0.9] Total throughput 29- 32 F4.2 --- T4 [0.5/0.9] Output flux within f/4 (1) 34- 37 F4.2 --- T4.4 [0.4/0.9] Output flux within f/4.4 (1) 39- 42 F4.2 --- T5 [0.3/0.9] Output flux within f/5 (1) 44- 47 F4.2 --- LFRD [0.04/0.3] FRD-induced throughput loss -------------------------------------------------------------------------------- Note (1): Divided by input flux within f/6.3. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 30-Oct-2018