# Technical Papers and Additional References

The documentation web pages describe the key features of APOGEE observations, data analysis, and data products, but, by necessity, the pages must be concise. The APOGEE technical papers provide more details and context for the APOGEE data.

The references that are required for all use of the APOGEE data are given in Required References, and our current full compilation of papers is given in All Technical Papers. References to convenience data products added to APOGEE data products are given in non-SDSS Data References. References to catalogs used for Targeting are summarized in Targeting References .

## Required References

In addition to the SDSS required references and acknowledgement, all users of APOGEE data should acknowledge the following publications in papers and presentations:

In addition, those using stellar parameters or chemical abundances need to cite the following publications:

Lastly, users should consider the list of papers below and cite those that are appropriate for their analyses, including appropriate references to non-SDSS data that are included in the SDSS catalogs for the convenience of the user (See Additional Non-SDSS Data).

### Other Acknowledgements

We encourage authors to use acknowledge facilities and software following the technical requirements of the Journal they are using. We further encourage authors to follow the advice in the Best Practices for Data Publication in the Astronomical Literature (Chen et al. 2021).

## All Technical Papers

### Current Data Release Papers

All papers using DR17 data are required to cite the following papers:

DR17 Data Release Description
Abdurro’uf et al. (2022) is the latest SDSS-IV data release paper, describing SDSS Data Release 17. The latest data release paper should always be used as the primary reference for most uses of SDSS data.
DR17 Pipeline and Data Release Description and Validation
Holtzman et al. (in prep.) provides extensive detail with regard to DR16-related modifications of the data reduction and ASPCAP pipelines and evaluates all DRP- and ASPCAP-generated data products (e.g., radial velocity values, stellar atmospheric parameters and individual element abundances).

### Overview

Publications using APOGEE-1 or APOGEE-2 data are required to cite the overview papers.

APOGEE Overview
Majewski et al. (2017) discusses the scientific motivation for the APOGEE-1 survey, the survey requirements, and the choice of survey fields. It describes survey operations, summarizes the level to which requirements are met, and references the data releases. Much of this information remains highly relevant for APOGEE-2.
APOGEE-2 Overview
Majewski et al. (in prep.) discusses the scientific motivation for the APOGEE-2 survey, its survey requirements, and choices relating to the programs that were initiated. It describes dual hemisphere survey operations, summarizes the level to which requirements are met, and references the data releases.

### Telescopes

The telescope can be identified for a target using the TELESCOPE tag. Users should reference the publications describing the telescopes that obtained the data in their samples.

SDSS 2.5m Telescope
Gunn et al. (2006) describes the technical setup for the SDSS 2.5-meter telescope.
NMSU 1m Telescope
Holtzman et al. (2010) describes the technical setup for the NMSU 1-meter telescope.
LCO 2.5m Telescope
Bowen and Vaughan (1973) describes the optical design of the Irénée du Pont Telescope at Las Campanas Observatory.

### Instrument & Hardware

All papers are required to cite the APOGEE Instruments paper. Other references are optional.

The APOGEE Instruments
Wilson et al. (2019) describes the technical details of the APOGEE-N and APOGEE-S instruments, themselves, and present instrument performance data. Prior to DR16, the reference was Wilson et al. (2012).
Fiber Development and FRD Testing
Brunner et al. (2010) describes technical details about the APOGEE fibers, optimization concerns, and testing the focal ratio degradation (FRD) required for the instrument.
VPH Grating
Arns et al. (2010) discusses the technical details of the VPH grating.
The Cryostat
Blank et al. (2010) describes technical considerations for and the design of the APOGEE cyrostat.

### Targeting

All papers are required to cite the appropriate targeting paper(s) from the list below. At a minimum, the survey-level strategies are described in Zasowski et al. (2013), Zasowski et al. (2017) , Beaton et al. (2021), and Santana et al. (2021). The other references may be more suitable for sub-samples.

APOGEE-1 Target Selection
Zasowski et al. (2013) discusses the target selection for main survey and APOGEE-1 ancillary science projects.

APOGEE-2 Target Selection
Zasowski et al. (2017) describes the APOGEE-2 field plan and explains in detail the targeting strategy employed for APOGEE-2N and APOGEE-2S.

• Pinsoneault et al. (2018) provides updates to the APOKASC program in APOGEE-2.
• Cottle et al. (2018) describes the target selection for the Young Clusters program in APOGEE-2.
• Nidever et al. (2020) describes the target selection for the Magellanic Clouds program in APOGEE-2. Though we note substantial expansions are described in Santana et al. (2021).
• Donor et al. (2018) provides an update for the Open Cluster Chemical Abundance and Mapping survey (OCCAM), including revisions to the target selection using early releases from Gaia.
Final APOGEE-2N Target Selection
Beaton et al. (2021) describes the final APOGEE-2N field plan, special programs in APOGEE-2N, and modifications to the target selection strategy undertaken to reach survey goals.
Final APOGEE-2S Target Selection
Santana et al. (2021) describes the final APOGEE-2S field plan, special programs in APOGEE-2S, and modifications to the target selection strategy undertaken to reach survey goals.

### Data Processing & RV Pipeline

APOGEE Data Reduction
Nidever et al. (2015) discusses the data reduction pipeline, describing how the raw data are analyzed to produce reduced, calibrated spectra. It also presents additional instrument performance data (flats, darks, LSF, persistence, etc.) and discusses the measurement of radial velocities and their quality.

• In DR17, a new procedure, "Doppler," was adopted for RV Measurements. This code is also available on github: github/dnidever/doppler
• The specific implementation of these codes for APOGEE data are available on github/sdss/apogee
NMSU 1-meter Data Processing
Holtzman et al. (2015) has sections discussing the 1-meter data processing, which differs slightly from that in the main survey.
The following papers address specific expansions or applications of our RV results that may be useful for other science applications:

• Deshpande et al. (2013) discusses specific requirements for the determination of M-dwarf stars with APOGEE data.
• Badenes et al. (2018) use the variation of RV for the APOGEE sample as a means to draw inference on the binary population. Technical descriptions and testing conducted in this paper are useful for evaluating the RV precision and variability.
• Price-Whelan et al. (2018, 2020, in prep.) use the individual epoch RVs to identify multiple star systems using The Joker (Price-Whelan et al. 2017, ASCL Entry, GitHub). Technical descriptions and testing conducted in this paper are useful for evaluating the RV precision and variability.
In DR16 and DR17, a Value-Added Catalog applied these methods to the full dataset and made those results fully public.

### Stellar Parameters & Abundances

All papers are required to cite the ASPCAP Overview paper alongside the Data Release paper that describes its current implementation. Users may also wish to acknowledge the underlying software for ASPCAP using "software" keywords as are described below.

ASPCAP Overview
Garcia Perez et al. (2016) describes how the spectra are analyzed to derive stellar parameters and abundances. It demonstrates validation of the overall method using simulated data and discusses uncertainties that are introduced by real-world issues: SNR, issues related computational efficiency, variation and uncertainty of the LSF, and issues involving the loss of information under skylines. It presents some basic tests of the methodology from very-high-resolution observations of some well-studied stars.

APOGEE Model Atmospheres
Jönsson et al. (2020) describes the model grid and the interpolation methods that were adopted in DR16 and DR17.

APOGEE Line List
The line list used for DR16 and DR17 was significantly expanded from previous efforts, this is described in Smith et al. (2021).
Additional papers discussing the line list development are as follows:

• The line list used for DR10-DR15 was described in Shetrone et al. (2015) , which also presents the details of how the H-band linelists, a critical component for ASPCAP, were developed.
• The APOGEE linelists were tested using high-resolution IR spectra of several well-studied stars in Smith et al. (2013).
• Further tests of the individual elements derived from the ASPCAP pipeline are found in Cunha et al. (2015).
• The identification and characterization of Neodymium is described in Hasselquist et al. (2016).
• The identification and characterization of Cerium is described Cunha et al. (2017)
APOGEE Spectral Grids
The DR17 spectral grids are described in Holtzman et al. (in prep). Additional supporting publications are:

Other papers describing the development of the spectral grids are as follows:

• The DR16 grids were described by Jönsson et al. (2020).
• Prior to DR16, Zamora et al. (2015) presents how the spectral synthesis was done, documents the libraries that have been used, and investigates the sensitivity of the result to the choice of synthesis code and model atmospheres.
• Mezaros et al. 2012 presented additional supporting material for the APOGEE spectral grids.
FERRE
Allende Prieto et al. (2006) describes FERRE, which is the spectral fitting engine used for ASPCAP. The code is available on github with its own documentation available (pdf; updated regularly).
The Cannon
The Cannon is described in Ness et al. (2015) and Casey et al. (2016).

### Data Release Papers

Users are required to cite the appropriate Data Release Paper.

APOGEE DR10 Calibration
Meszaros et al. (2013) discusses calibration of stellar parameters that were released in DR10.
APOGEE DR12 Data
Holtzman et al. (2015) describes the APOGEE data contained in DR12 of in SDSS-III.
APOGEE DR13/DR14 Data
Holtzman et al. (2018) provides extensive detail with regard to DR13- and DR14-related modifications of the data reduction and ASPCAP pipelines and evaluates all DRP- and ASPCAP-generated data products (e.g., radial velocity values, stellar atmospheric parameters and individual element abundances).
DR13/DR14 Validation
Jönsson et al. (2018) compares DR13 and DR14 ASPCAP-derived parameters with various optical abundance analyses from the literature.
DR16 Data
Jönsson et al. (2020) is the DR16 data release paper that describes the processing and data analysis employed.
DR17 Data
Holtzman et al. (in prep.) is the DR17 APOGEE data release paper that describes the processing and data analysis employed.

## Additional non-SDSS Data Products in APOGEE Catalogs

The APOGEE data products contain some data adopted from other major observational programs. In this section, we provide references for those surveys or methods. Typically, these data are provided for a large fraction of the APOGEE targets. Data that was specifically use for targeting only is summarized in Targeting References.

#### Gaia EDR3 References

Gaia Mission
Gaia Collaboration, Prusti et al. (2016) provides a description of the Gaia mission, including the spacecraft, instruments, survey, and measurement principles.
Gaia EDR3
Gaia EDR3 Astrometry
Lindegren et al. (2021) provides the description of the Gaia EDR3 Astrometric Solution.
Gaia EDR3 Photometry
Riello et al. (2021) provides a description of the Gaia EDR3 Photometric System.
Seabroke et al. (2021) provides a description of the updates to the Gaia DR2 radial velocities as presented in Gaia EDR3.
Distances
Bailer-Jones et al. (2021) is a catalog of geometric distances derived from Gaia EDR3 parallax data using rigorous statistical methods.

#### Photometry

2MASS
The canonical paper for 2MASS is Skrutskie et al. (2006) and the acknowledgement is provided on the 2MASS IPAC webpage.
WISE
Wright et al. (2010) describes the WISE mission and spacecraft and the AllWise catalog is cited as Cutri et al. (2013). The acknowledgement is provided on the WISE2 IPAC Webpage and the AllWise IPAC Webpage.
Spitzer
Werner et al. (2004) describes the Spitzer Space Telescope and Mission. The IRAC instrument is described in Fazio et al. (2004). In particular, APOGEE targeting in the disk and Bulge makes use of data products from Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). Acknowledgements for Spitzer are described on the Spitzer IRAC Webpage.
Washington+DDO51
The Washington+DDO51 photometry included in the summary files is described in Zasowksi et al. (2013).
Those using these data may also include the following acknowledgement: "The APOGEE project thanks Jeff Munn (NOFS) for collecting Washington$+DDO51$ imaging for large areas of the sky."

#### Reddening and Extinction

$E(B-V)$
$E(B-V)$ estimates are provided from the maps of Schlegel, Finkbeiner, and Davis (1998).
RJCE
The Rayleigh-Jeans Color Excess method is also employed to estimate $A_{K}$ using 2MASS with either WISE or Spitzer photometry and the method is described in Majewski, Zasowski, and Nidever (2011) with some additional modifications described in Zasowksi et al. (2013).

## Targeting Catalog References

For some scientific purposes, having an understanding of the input targeting references can be important as these guided the target's selection. Two parameters are important: (1) the input photometry catalog (sets the exposure time) and (2) proper motion catalogs (proper motion corrections are applied to the position).

### Photometry Catalog References

The targeting photometry references are coded into the SRC_H tag in the summary catalogs. Full information can be found in the intermediate targeting files on the SAS (see Data Access for more details).

The Targeting Team has provided a DR17 H_SRC Table (PDF with hyperlinks) that provides the SRC_H values, a description of the source and the application, and the appropriate references, when possible. This Table was constructed from the intermediate targeting files and, thus, includes all input SRC_H values irregardless of if they appear in the final output catalogs.

### Proper Motion Catalog References

The input proper motion catalog references are provided both in the intermediate targeting files on the SAS (see Data Access for more details). These may be important for many scientific applications because these proper motions are used to determine the coordinates of the target at the epoch of observation.

The Targeting Team has provided a DR17 TARG_PM_SRC Table (PDF with Hyperlinks) that provides the TARG_PM_SRC values, a description of the source and the application, and the appropriate references, when possible. This Table was constructed from the intermediate targeting files and, thus, includes all input TARG_PM_SRC values irregardless of if they appear in the final output catalogs.