Spectrophotometry with Hectospec, the MMT's Fiber-Fed Spectrograph

Fabricant, Daniel G.; Kurtz, Michael J.; Geller, Margaret J.; Caldwell, Nelson; Woods, D.; Dell’Antonio, Ian

doi:10.1086/593023

Cited by 50 publications

(68 citation statements)

References 45 publications

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“…The spectra were corrected to relative fluxes using standard star measurements taken at irregular intervals during the observation period. The spectrograph throughput was remarkably consistent over this period (Fabricant et al 2008), thus we are confident in the corrections to fluxed spectra. The fluxing process was needed only for determining the reddening values.…”

Section: Hectospec Observationssupporting

confidence: 56%

Star Clusters in M31. Ii. Old Cluster Metallicities and Ages From Hectospec Data

Caldwell

Schiavon

Morrison

et al. 2011

The Astronomical Journal

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400

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We present new high signal-to-noise spectroscopic data on the M31 globular cluster (GC) system, obtained with the Hectospec multifiber spectrograph on the 6.5 m MMT. More than 300 clusters have been observed at a resolution of 5 Å and with a median S/N of 75 per Å, providing velocities with a median uncertainty of 6 km s −1 . The primary focus of this paper is the determination of mean cluster metallicities, ages, and reddenings. Metallicities were estimated using a calibration of Lick indices with [Fe/H] provided by Galactic GCs. These match well the metallicities of 24 M31 clusters determined from Hubble Space Telescope color-magnitude diagrams, the differences having an rms of 0.2 dex. The metallicity distribution is not generally bimodal, in strong distinction with the bimodal Galactic globular distribution. Rather, the M31 distribution shows a broad peak, centered at [Fe/H] = −1, possibly with minor peaks at [Fe/H] = −1.4, −0.7, and −0.2, suggesting that the cluster systems of M31 and the Milky Way had different formation histories. Ages for clusters with [Fe/H] > −1 were determined using the automatic stellar population analysis program EZ_Ages. We find no evidence for massive clusters in M31 with intermediate ages, those between 2 and 6 Gyr. Moreover, we find that the mean ages of the old GCs are remarkably constant over about a decade in metallicity (−0.95 [Fe/H] 0.0).

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Section: Hectospec Observationssupporting

confidence: 56%

Star Clusters in M31. Ii. Old Cluster Metallicities and Ages From Hectospec Data

Caldwell

Schiavon

Morrison

et al. 2011

The Astronomical Journal

Self Cite

166

400

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“…Fabricant et al (2008) show that D 4000 n measured from Hectospec and SDSS spectroscopy are consistent to within~5%. This level of consistency is sufficient for our application.…”

Section: Nmentioning

confidence: 67%

“…Although A2029 appears relaxed in the optical, X-ray observations reveal an extended X-ray sloshing spiral structure indicative of complex internal dynamics in the intracluster medium (Clarke et al 2004;Walker et al 2012;Paterno-Mahler et al 2013). To study the statistical properties of A2029 member galaxies, we carry out a redshift survey using Hectospec (Fabricant et al 2008), a wide-field spectrograph on the 6.5 m MMT.…”

Section: A2029mentioning

confidence: 99%

The Velocity Dispersion Function of Very Massive Galaxy Clusters: Abell 2029 and Coma

Sohn¹,

Geller²,

Zahid³

et al. 2017

ApJS

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107

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Based on an extensive redshift survey for galaxy clusters Abell 2029 and Coma, we measure the luminosity functions (LFs) and stellar mass functions (SMFs) for the entire cluster member galaxies. Most importantly, we measure the velocity dispersion functions (VDFs) for quiescent members. The MMT/Hectospec redshift survey for galaxies in A2029 identifies 982 spectroscopic members; for 838 members, we derive the central velocity dispersion from the spectroscopy. Coma is the only other cluster surveyed as densely. The LFs, SMFs, and VDFs for A2029 and Coma are essentially identical. The SMFs of the clusters are consistent with simulations. The A2029 and Coma VDFs for quiescent galaxies have a significantly steeper slope than those of field galaxies for velocity dispersion  -100 km s 1 . The cluster VDFs also exceed the field at velocity dispersion  -250 km s 1 . The differences between cluster and field VDFs are potentially important tests of simulations and of the formation of structure in the universe.

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“…This program fits a polynomial continuum (S continuum = A λ × (λ/λ 0 ) α λ ) and a Gaussian around the redshifted C iv, Mg ii, and Hβ regions, based on the HSRED or SpecObj redshifts (see also Section 3). Objects are kept as quasar candidates if they have at least one BEL (FWHM > 1000 km s −1 ; Schneider et al 2007) in the secure spectral ranges with limited atmospheric extinction and instrument errors: 3850-8400 Å (Fabricant et al 2008) for MMT targets and 3850-9000 Å (Stoughton et al 2002) for SDSS targets. Outside these ranges, the spectra start to be bounded by sky-subtraction errors and are therefore not reliable.…”

Section: Broad-line Object Identificationmentioning

confidence: 99%

“…The non-Gaussian, flat-topped fiber profile of MMT Hectospec (Fabricant et al 2008) renders this correction imperfect and will be discussed in the absorption paper (Y. S. Dai et al, in preparation). We adopt the Monte Carlo flux randomization method as in the SDSS routine (S11).…”

Section: Uncertainties Of Spectral Measurements and Error Estimatesmentioning

confidence: 99%

Mid-Infrared-Selected Quasars. I. Virial Black Hole Mass and Eddington Ratios

Dai

Elvis

Bergeron

et al. 2014

ApJ

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We provide a catalog of 391 mid-infrared-selected (MIR; 24 μm) broad-emission-line (BEL; type 1) quasars in the 22 deg 2 SWIRE Lockman Hole field. This quasar sample is selected in the MIR from Spitzer MIPS with S 24 > 400 μJy, jointly with an optical magnitude limit of r (AB) < 22.5 for broad line identification. The catalog is based on MMT and Sloan Digital Sky Survey (SDSS) spectroscopy to select BEL quasars, extending the SDSS coverage to fainter magnitudes and lower redshifts, and recovers a more complete quasar population. The MIR-selected quasar sample peaks at z ∼ 1.4 and recovers a significant and constant (20%) fraction of extended objects with SDSS photometry across magnitudes, which were not included in the SDSS quasar survey dominated by point sources. This sample also recovers a significant population of z < 3 quasars at i > 19.1. We then investigate the continuum luminosity and line profiles of these MIR quasars, and estimate their virial black hole masses and the Eddington ratios. The supermassive black hole mass shows evidence of downsizing, although the Eddington ratios remain constant at 1 < z < 4. Compared to point sources in the same redshift range, extended sources at z < 1 show systematically lower Eddington ratios. The catalog and spectra are publicly available online.

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Spectrophotometry with Hectospec, the MMT's Fiber-Fed Spectrograph

Cited by 50 publications

References 45 publications

Star Clusters in M31. Ii. Old Cluster Metallicities and Ages From Hectospec Data

Star Clusters in M31. Ii. Old Cluster Metallicities and Ages From Hectospec Data

The Velocity Dispersion Function of Very Massive Galaxy Clusters: Abell 2029 and Coma

Mid-Infrared-Selected Quasars. I. Virial Black Hole Mass and Eddington Ratios

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