Mission Overview

 

COS Legacy Archive Spectroscopic SurveY (CLASSY)

 

Primary Investigators: Danielle Berg, John Chisholm, Bethan James, Tim Heckman, Crystal Martin, Dan Stark

HLSP Website Authors: Danielle Berg, Bethan James, Meaghan McDonald, Teagan King

Released: 2022-03-15

Updated: 2022-03-15

Primary Reference(s): Berg et al. 2019

DOI: 10.17909/m3fq-jj25

Citations: See ADS Statistics

Source Data: 

CLASSY Coadded FUV Spectra

Final co-added absorption UV spectra from CLASSY observations. Vertical lines denote the following lines: blue = ISM, orange dashed = nebular, green dashed = wind.

CLASSY Coadded FUV Spectra

Final co-added emission FUV spectra from CLASSY observations. Vertical lines denote the following lines: blue = ISM, orange dashed = nebular, green dashed = wind.

Overview

 

Far-UV spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope (JWST) and construction of the extremely large telescopes (ELTs) will soon usher in a new era, pushing the UV spectroscopic frontier to z~15-20. The success of these future endeavors hinges on a comprehensive understanding of the massive star populations and interstellar medium (ISM) gas conditions that power the observed UV spectral features. This requires the level of detail that is only possible in local galaxies.  

The COS Legacy Spectroscopic SurveY (CLASSY) is a treasury survey that builds on the Hubble Space Telescope (HST) archive to construct the first high-quality, high-resolution far-ultraviolet (far-UV) spectral database of 45 nearby star-forming galaxies. The survey combines 177 orbits of archival observations with 135 new orbits (312 total orbits) of HST observations, or more than 600 total spectral images taken with the Cosmic Origins Spectrograph (COS). The CLASSY Treasury sample contains 45 star-forming galaxies selected to span similar properties as seen at high redshift, with a large range of masses, metallicities, ionization parameters, and densities, but enhanced star formation rates. The CLASSY spectral atlas contains a suite of emission and absorption features that enable investigations of the massive stellar population properties, the physical properties of large-scale outflows that regulate star formation, and the chemical abundance patterns of the gas and stars. Further, CLASSY will improve the diagnostic power of the rest-frame UV lines for use by future JWST/ELT surveys, providing a long-lasting legacy to the astronomical community for decades to come.

The main objective of CLASSY is to use FUV spectra to unify stellar and gas-phase physics, allowing a holistic understanding of massive stars as the drivers of the gaseous evolution of star-forming galaxies. Naturally, the pursuit of this goal will produce a number of additional HLSPs beyond the coadded spectra that will be useful to the astronomical community. Therefore, the enduring value and utility of CLASSY will reside in these state-of-the-art HLSPs products. 

 

Summary of Planned CLASSY Deliverables:

  • CLASSY spectral atlas 

  • Compiled ancillary data 

  • CLASSY stellar continuum fits

  • Database of emission and absorption feature properties

  • Database of Lyα emission profile fits

  • Database of tailored photoionization models

  • Database of nebular properties

  • UV Diagnostic Tools

  • Database of tailored chemical evolution models

  • Database of feedback properties

  • Predictive tools of inferred LyC escape fractions %of ionizing photons

  • Improved stellar models and prescriptions

  • User-friendly CLASSY tutorials on interacting with and utilizing the HLSPs

 

CLASSY Target Properties

CLASSY Target Properties

Target properties of the 45 CLASSY targets, including RA, Dec, redshift, stellar mass, star formation rate.
CLASSY Observation Details

CLASSY Observation Details

View details on COS observations of CLASSY targets, including dataset names, exposure times, grating, wavelength coverage, and more.
Download CLASSY Data

Download CLASSY Data

MAST tool to download CLASSY data, including subset selection based on target properties, observation parameters, or file type.

           

CLASSY Images

HST/COS NUV acquisition images for the CLASSY sample are shown in blue, overlaid on top of the red-yellow SDSS r-band images (when available, see Berg+2021 for exceptions). The 2.5” COS aperture used for the UV spectra are shown as blue circles, closely matching the SDSS 3” optical aperture in orange.

J0021+0052
J0021+0052
  • Pos: 00:21:01 +00:52:48
  • Redshift: 0.098393
  • log M 9.09 M
  • log SFR 1.07 yr-1
  • Metallicity: 0.30 Z/Z

View

J0036-3333
J0036-3333
  • Pos: 00:36:53 -33:33:17
  • Redshift: 0.020598
  • log M 9.14 Msol
  • log SFR 1.01 yr-1
  • Metallicity: 0.33 Z/Z

View

J0127-0619
J0127-0619
  • Pos: 01:27:36 -06:19:36
  • Redshift: 0.005400
  • log M:  8.74 Msol
  • log SFR:  -0.75 yr-1
  • Metallicity: 0.10 Z/Z

View

J0144+0453
J0144+0453
  • Pos: 01:44:41 +04:53:25
  • Redshift: 0.005200
  • log M:  7.65 Msol
  • log SFR:  -0.81 yr-1
  • Metallicity: 0.12 Z/Z

View

J0337-0502
J0337-0502
  • Pos: 03:37:44 -05:02:39
  • Redshift: 0.013520
  • log M:  7.06 Msol
  • log SFR:  -0.32 yr-1
  • Metallicity: 0.06 Z/Z

View

J0405-3648
J0405-3648
  • Pos: 04:05:20-36:48:59
  • Redshift: 0.002800
  • log M:  6.61 Msol
  • log SFR:  -1.81 yr-1
  • Metallicity: 0.02 Z/Z

View

J0808+3948
J0808+3948
  • Pos: 08:08:44+39:48:53
  • Redshift: 0.091230
  • log M:  9.12 Msol
  • log SFR:  1.26 yr-1
  • Metallicity: 1.20 Z/Z

View

J0823+2806
J0823+2806
  • Pos: 08:23:55+28:06:22
  • Redshift: 0.047223
  • log M:  9.38 Msol
  • log SFR:  1.48 yr-1
  • Metallicity: 0.39 Z/Z

View

J0926+4427
J0926+4427
  • Pos: 09:26:00+44:27:37
  • Redshift: 0.180667
  • log M:  8.76 Msol
  • log SFR:  1.03 yr-1
  • Metallicity: 0.25 Z/Z

View

J0934+5514
J0934+5514
  • Pos: 09:34:02+55:14:28
  • Redshift: 0.002500
  • log M:  6.27 Msol
  • log SFR: -1.52 yr-1
  • Metallicity: 0.02 Z/Z

View

J0938+5428
J0938+5428
  • Pos: 09:38:13+54:28:25
  • Redshift: 0.102102
  • log M:  9.15 Msol
  • log SFR:  1.05 yr-1
  • Metallicity: 0.36 Z/Z

View

J0940+2935
J0940+2935
  • Pos: 09:40:13+29:35:30
  • Redshift: 0.001675
  • log M:  6.71 Msol
  • log SFR:  -2.01 yr-1
  • Metallicity: 0.09 Z/Z

View

J0942+3547
J0942+3547
  • Pos: 09:42:53+35:47:26
  • Redshift: 0.014857
  • log M:  7.56 Msol
  • log SFR:  -0.76 yr-1
  • Metallicity: 0.28 Z/Z

View

J0944-0038
J0944-0038
  • Pos: 09:44:02-00:38:32
  • Redshift: 0.004776
  • log M:  6.83 Msol
  • log SFR:  -0.78 yr-1
  • Metallicity: 0.14 Z/Z

View

J0944+3424
J0944+3424
  • Pos: 09:44:26+34:42:08
  • Redshift: 0.020046
  • log M:  8.19 Msol
  • log SFR:  -0.01 yr-1
  • Metallicity: 0.09 Z/Z

View

J1016+3754
J1016+3754
  • Pos: 10:16:24+37:54:46
  • Redshift: 0.003879
  • log M:  6.72 Msol
  • log SFR:  -1.17 yr-1
  • Metallicity: 0.07 Z/Z

View

J1024+0524
J1024+0524
  • Pos: 10:24:29+05:24:51
  • Redshift: 0.033191
  • log M:  7.89 Msol
  • log SFR:  0.21 yr-1
  • Metallicity: 0.14 Z/Z

View

J1025+3622
J1025+3622
  • Pos: 10:25:48+36:22:58
  • Redshift: 0.126500
  • log M:  8.87 Msol
  • log SFR:  1.04 yr-1
  • Metallicity: 0.28 Z/Z

View

J1044+0353
J1044+0353
  • Pos: 10:44:58+03:53:13
  • Redshift: 0.012870
  • log M:  6.80 Msol
  • log SFR:  -0.59 yr-1
  • Metallicity: 0.06 Z/Z

View

J1105+4444
J1105+4444
  • Pos: 11:05:08+44:44:47
  • Redshift: 0.021540
  • log M:  8.98 Msol
  • log SFR:  0.69 yr-1
  • Metallicity: 0.35 Z/Z

View

J1112+5503
J1112+5503
  • Pos: 11:12:44+55:03:47
  • Redshift: 0.020598
  • log M:  9.59 Msol
  • log SFR:  1.60 yr-1
  • Metallicity: 0.58 Z/Z

View

J1119+5130
J1119+5130
  • Pos: 11:19:34+51:30:12
  • Redshift: 0.004458
  • log M:  6.77 Msol
  • log SFR:  -1.58 yr-1
  • Metallicity: 0.08 Z/Z

View

J1129+2034
J1129+2034
  • Pos: 11:29:14+20:34:52
  • Redshift: 0.004703
  • log M:  8.09 Msol
  • log SFR:  -0.37 yr-1
  • Metallicity: 0.39 Z/Z

View

J1132+5722
J1132+5722
  • Pos: 11:32:03+57:22:36
  • Redshift: 0.005041
  • log M:  7.31 Msol
  • log SFR:  -1.07 yr-1
  • Metallicity: 0.08 Z/Z

View

J1132+1411
J1132+1411
  • Pos: 11:32:35+14:11:30
  • Redshift: 0.017637
  • log M:  8.68 Msol
  • log SFR:  0.44 yr-1
  • Metallicity: 0.36 Z/Z

View

J1144+4012
J1144+4012
  • Pos: 11:44:22+40:12:21
  • Redshift: 0.126947
  • log M:  9.89 Msol
  • log SFR:  1.51 yr-1
  • Metallicity: 0.55 Z/Z

View

J1148+2546
J1148+2546
  • Pos: 11:48:27+25:46:12
  • Redshift: 0.045117
  • log M:  8.14 Msol
  • log SFR:  0.53 yr-1
  • Metallicity: 0.18 Z/Z

View

J1150+1501
J1150+1501
  • Pos: 11:50:03+15:01:23
  • Redshift: 0.002448
  • log M:  6.84 Msol
  • log SFR:  -1.33 yr-1
  • Metallicity: 0.28 Z/Z

View

J1157+3220
J1157+3220
  • Pos: 11:57:32+32:20:30
  • Redshift: 0.010970
  • log M:  9.04 Msol
  • log SFR:  0.97 yr-1
  • Metallicity: 0.55 Z/Z

View

J1200+1343
J1200+1343
  • Pos: 12:00:33+13:43:08
  • Redshift: 0.066750
  • log M:  8.12 Msol
  • log SFR:  0.75 yr-1
  • Metallicity: 0.37 Z/Z

View

J1225+6109
J1225+6109
  • Pos: 12:25:05+61:09:11
  • Redshift: 0.002341
  • log M:  7.12 Msol
  • log SFR:  -1.08 yr-1
  • Metallicity: 0.19 Z/Z

View

J1253-0312
J1253-0312
  • Pos: 12:53:06-03:12:59
  • Redshift: 0.022723
  • log M:  7.65 Msol
  • log SFR: 0.56 yr-1
  • Metallicity: 0.23 Z/Z

View

J1314+3452
J1314+3452
  • Pos: 13:14:47+34:52:60
  • Redshift: 0.002885
  • log M:  7.56 Msol
  • log SFR:  -0.67 yr-1
  • Metallicity: 0.37 Z/Z

View

J1323-0132
J1323-0132
  • Pos: 13:23:48-01:32:52
  • Redshift: 0.022464
  • log M:  6.31 Msol
  • log SFR:  -0.72 yr-1
  • Metallicity: 0.10 Z/Z

View

J1359+5726
J1359+5726
  • Pos: 13:59:51+57:26:23
  • Redshift 0.033829
  • log M 8.41 Msol
  • log SFR 0.42 yr-1
  • Metallicity: 0.19 Z/Z

View

J1416+1223
J1416+1223
  • Pos: 14:16:13+12:23:40
  • Redshift: 0.123156
  • log M:  9.59 Msol
  • log SFR:  1.57 yr-1
  • Metallicity: 0.69 Z/Z

View

J1418+2102
J1418+2102
  • Pos: 14:18:51+21:02:40
  • Redshift: 0.008550
  • log M:  6.22 Msol
  • log SFR:  -1.13 yr-1
  • Metallicity: 0.11 Z/Z

View

J1428+1653
J1428+1653
  • Pos: 14:28:56+16:53:39
  • Redshift: 0.181666
  • log M:  9.56 Msol
  • log SFR:  1.22 yr-1
  • Metallicity: 0.44 Z/Z

View

J1429+0643
J1429+0643
  • Pos: 14:29:47+06:43:35
  • Redshift: 0.173502
  • log M:  8.80 Msol
  • log SFR:  1.42 yr-1
  • Metallicity: 0.26 Z/Z

View

J1444+4237
J1444+4237
  • Pos: 14:44:11+42:37:36
  • Redshift: 0.002300
  • log M:  6.48 Msol
  • log SFR:  -1.94 yr-1
  • Metallicity: 0.09 Z/Z

View

J1448-0110
J1448-0110
  • Pos: 14:48:05-01:10:58
  • Redshift: 0.027412
  • log M:  7.61 Msol
  • log SFR:  0.39 yr-1
  • Metallicity: 0.28 Z/Z

View

J1521+0759
J1521+0759
  • Pos: 15:21:42+07:59:22
  • Redshift: 0.094261
  • log M:  9.00 Msol
  • log SFR:  0.95 yr-1
  • Metallicity: 0.42 Z/Z

View

J1525+0757
J1525+0757
  • Pos: 15:25:22+07:57:20
  • Redshift: 0.075791
  • log M:  10.10 Msol
  • log SFR:  1.00 yr-1
  • Metallicity: 0.44 Z/Z

View

J1545+0858
J1545+0858
  • Pos: 15:45:43+08:58:01
  • Redshift: 0.037724
  • log M:  7.52 Msol
  • log SFR:  0.37 yr-1
  • Metallicity: 0.11 Z/Z

View

J1612+0817
J1612+0817
  • Pos: 16:12:46+08:17:01
  • Redshift: 0.149143
  • log M:  9.78 Msol
  • log SFR:  1.58 yr-1
  • Metallicity: 0.31 Z/Z

View

Data Products

CLASSY was constructed to provide a critical legacy data set to the community that can be used for many years to come. Under this umbrella, we provide the research community with several high level science products (HLSPs) for each CLASSY target, which are listed below. The primary deliverable is co-added UV spectra for each target (derived from CLASSY program GO-15840 and archival programs) at multiple spectral resolutions (see Berg+2021 and James+2021 for more details). For more information on data products and their respective file extensions, click here

Data file naming convention:

hlsp_classy_hst_cos_<target>_multi_v1_<ext>

where:

  • <target> = CLASSY target name
  • <ext> = The high level science product file type extension

File types:

_coadded.fits Co-added UV spectra

Data Access

CLASSY data products are available to download below. To download a tarball of HLSPs use the ‘Download All CLASSY data’ button. To download a subset of CLASSY products based on target properties, observation parameters, or file type, click the ‘MAST Query Tool’ button.

Download all CLASSY data

Download All CLASSY Data

Download tarball of CLASSY HLSPs
MAST Query Tool

Search & Download CLASSY Data

Search and download CLASSY data products via the MAST query tool

Tutorials

 

Access Jupyter Notebook tutorials to interact with CLASSY HLSPs using Python. Click the links below to view the notebook in your browser, or download the notebook to your local computer and work through the steps on your own. Check back for additional notebook releases as more CLASSY HLSPs are released.

NOTE: This notebook was created and contributed by the CLASSY team.  MAST makes this notebook available "as-is" and does not take responsibility for its maintenance.

Plot CLASSY Spectra

Plot multi-grating co-added spectra using a Jupyter Notebook

Download Notebook

Spectra

Interactive HST/COS CLASSY spectra, combining archival and new FUV G130M+G160M+G185M observations. Note that chip gaps are indicated by blank spaces and that Milky Way absorption features and geocoronal lines are still present. By zooming in on different regions of the spectrum, you will see different stellar, ISM, and nebular features. Some of the common features are marked by colored bands and are labeled when you hover. You can click on the different types of spectral features in the legend to turn them on and off.

Citations

If you use CLASSY data in a published work, please cite the following:

For any use of CLASSY data:

  • CLASSY Website

  • CLASSY I: Berg et al. 2022

  • CLASSY II: James et al. 2022 

  • CLASSY III: Xu et al. 2022, submitted

  • CLASSY IV: Mingozzi et al. 2022

For use of the coadded spectra HLSPs: 

For use of the stellar continuum fits HLSPs:

  • CLASSY III: Xu et al. 2022, submitted

For use of the UV emission lines HLSPs:

  • TBD

For use of the optical emission lines HLSPs:

  • TBD

For use of the LyA HLSPs:

  • TBD

For use of the nebular properties HLSPs:

  • TBD

For use of the UV Diagnostic HLSPs:

  • TBD

For use of the photoionization model HLSPs:

  • TBD

For use of the chemical evolution HLSPs:

  • TBD

For use of the feedback properties HLSPs:

  • TBD

 

Note: These HLSP data products are licensed for use under CC BY 4.0.

References

List of CLASSY publications:

Acknowledgments

We extend our gratitude to the Lorentz Center for useful discussions during the “Characterizing Galaxies with Spectroscopy with a view for JWST” 2017 workshop that led to the formation of the CLASSY collaboration and survey.

We are sincerely grateful to the MAST team at STScI and their expertise in developing the MAST Search Tool for use with CLASSY data.