Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy

Jean Michel Deharveng, Todd Small, Tom A. Barlow, Céline Péroux, Bruno Milliard, Peter G. Friedman, D. Christopher Martin, Patrick Morrissey, David Schiminovich, Karl Forster, Mark Seibert, Ted K. Wyder, Luciana Bianchi, Jose Donas, Timothy M. Heckman, Young Wook Lee, Barry F. Madore, Susan G. Neff, R. Michael Rich, Alex S. SzalayBarry Y. Welsh, Sukyoung K. Yi

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Abstract

We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ∼8 Å in the far-ultraviolet (FUV; 1350-1750 Å) and ∼20 Å in the near-ultraviolet (NUV; 1950-2750 Å) for a systematic search of Lyα-emitting galaxies at low redshift. Our aim is to fill a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in five deep exposures (5.65 deg2) has resulted in 96 Lyα-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs. The Lyα equivalent widths (EWs) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, with the exception of a possible decrease in the most luminous objects that may be due to small-number statistics. The objects' distribution in EW is similar to that at z ∼ 3, but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a subsample of 66 objects in the range 0.2 < z < 0.35 has been used to build a Lyα luminosity function (LF). The incompleteness due to objects with significant Lyα emission but a UV continuum too low for spectral extraction has been evaluated. A comparison with Hα LFs in the same redshift domain is consistent with an average Lya/Ha of ∼1 in about 15% of the star-forming galaxies. A comparison with high-redshift Lyα LFs implies an increase of the Lya luminosity density by a factor of about 16 from z ∼ 0.3 to z ∼ 3. By comparison with the factor of 5 increase in the UV luminosity density in the same redshift range, this suggests an increase of the average Lyα escape fraction with redshift.

Original languageEnglish
Pages (from-to)1072-1082
Number of pages11
JournalAstrophysical Journal
Volume680
Issue number2
DOIs
Publication statusPublished - 2008 Jun 20

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spectroscopy
galaxies
luminosity
stars
escape
universe
statistics
continuums
trends
color
prediction
comparison
predictions

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Deharveng, J. M., Small, T., Barlow, T. A., Péroux, C., Milliard, B., Friedman, P. G., ... Yi, S. K. (2008). Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy. Astrophysical Journal, 680(2), 1072-1082. https://doi.org/10.1086/587953
Deharveng, Jean Michel ; Small, Todd ; Barlow, Tom A. ; Péroux, Céline ; Milliard, Bruno ; Friedman, Peter G. ; Martin, D. Christopher ; Morrissey, Patrick ; Schiminovich, David ; Forster, Karl ; Seibert, Mark ; Wyder, Ted K. ; Bianchi, Luciana ; Donas, Jose ; Heckman, Timothy M. ; Lee, Young Wook ; Madore, Barry F. ; Neff, Susan G. ; Rich, R. Michael ; Szalay, Alex S. ; Welsh, Barry Y. ; Yi, Sukyoung K. / Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy. In: Astrophysical Journal. 2008 ; Vol. 680, No. 2. pp. 1072-1082.
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abstract = "We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ∼8 {\AA} in the far-ultraviolet (FUV; 1350-1750 {\AA}) and ∼20 {\AA} in the near-ultraviolet (NUV; 1950-2750 {\AA}) for a systematic search of Lyα-emitting galaxies at low redshift. Our aim is to fill a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in five deep exposures (5.65 deg2) has resulted in 96 Lyα-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs. The Lyα equivalent widths (EWs) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, with the exception of a possible decrease in the most luminous objects that may be due to small-number statistics. The objects' distribution in EW is similar to that at z ∼ 3, but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a subsample of 66 objects in the range 0.2 < z < 0.35 has been used to build a Lyα luminosity function (LF). The incompleteness due to objects with significant Lyα emission but a UV continuum too low for spectral extraction has been evaluated. A comparison with Hα LFs in the same redshift domain is consistent with an average Lya/Ha of ∼1 in about 15{\%} of the star-forming galaxies. A comparison with high-redshift Lyα LFs implies an increase of the Lya luminosity density by a factor of about 16 from z ∼ 0.3 to z ∼ 3. By comparison with the factor of 5 increase in the UV luminosity density in the same redshift range, this suggests an increase of the average Lyα escape fraction with redshift.",
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Deharveng, JM, Small, T, Barlow, TA, Péroux, C, Milliard, B, Friedman, PG, Martin, DC, Morrissey, P, Schiminovich, D, Forster, K, Seibert, M, Wyder, TK, Bianchi, L, Donas, J, Heckman, TM, Lee, YW, Madore, BF, Neff, SG, Rich, RM, Szalay, AS, Welsh, BY & Yi, SK 2008, 'Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy', Astrophysical Journal, vol. 680, no. 2, pp. 1072-1082. https://doi.org/10.1086/587953

Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy. / Deharveng, Jean Michel; Small, Todd; Barlow, Tom A.; Péroux, Céline; Milliard, Bruno; Friedman, Peter G.; Martin, D. Christopher; Morrissey, Patrick; Schiminovich, David; Forster, Karl; Seibert, Mark; Wyder, Ted K.; Bianchi, Luciana; Donas, Jose; Heckman, Timothy M.; Lee, Young Wook; Madore, Barry F.; Neff, Susan G.; Rich, R. Michael; Szalay, Alex S.; Welsh, Barry Y.; Yi, Sukyoung K.

In: Astrophysical Journal, Vol. 680, No. 2, 20.06.2008, p. 1072-1082.

Research output: Contribution to journalArticle

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T1 - Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy

AU - Deharveng, Jean Michel

AU - Small, Todd

AU - Barlow, Tom A.

AU - Péroux, Céline

AU - Milliard, Bruno

AU - Friedman, Peter G.

AU - Martin, D. Christopher

AU - Morrissey, Patrick

AU - Schiminovich, David

AU - Forster, Karl

AU - Seibert, Mark

AU - Wyder, Ted K.

AU - Bianchi, Luciana

AU - Donas, Jose

AU - Heckman, Timothy M.

AU - Lee, Young Wook

AU - Madore, Barry F.

AU - Neff, Susan G.

AU - Rich, R. Michael

AU - Szalay, Alex S.

AU - Welsh, Barry Y.

AU - Yi, Sukyoung K.

PY - 2008/6/20

Y1 - 2008/6/20

N2 - We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ∼8 Å in the far-ultraviolet (FUV; 1350-1750 Å) and ∼20 Å in the near-ultraviolet (NUV; 1950-2750 Å) for a systematic search of Lyα-emitting galaxies at low redshift. Our aim is to fill a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in five deep exposures (5.65 deg2) has resulted in 96 Lyα-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs. The Lyα equivalent widths (EWs) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, with the exception of a possible decrease in the most luminous objects that may be due to small-number statistics. The objects' distribution in EW is similar to that at z ∼ 3, but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a subsample of 66 objects in the range 0.2 < z < 0.35 has been used to build a Lyα luminosity function (LF). The incompleteness due to objects with significant Lyα emission but a UV continuum too low for spectral extraction has been evaluated. A comparison with Hα LFs in the same redshift domain is consistent with an average Lya/Ha of ∼1 in about 15% of the star-forming galaxies. A comparison with high-redshift Lyα LFs implies an increase of the Lya luminosity density by a factor of about 16 from z ∼ 0.3 to z ∼ 3. By comparison with the factor of 5 increase in the UV luminosity density in the same redshift range, this suggests an increase of the average Lyα escape fraction with redshift.

AB - We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ∼8 Å in the far-ultraviolet (FUV; 1350-1750 Å) and ∼20 Å in the near-ultraviolet (NUV; 1950-2750 Å) for a systematic search of Lyα-emitting galaxies at low redshift. Our aim is to fill a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in five deep exposures (5.65 deg2) has resulted in 96 Lyα-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs. The Lyα equivalent widths (EWs) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, with the exception of a possible decrease in the most luminous objects that may be due to small-number statistics. The objects' distribution in EW is similar to that at z ∼ 3, but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a subsample of 66 objects in the range 0.2 < z < 0.35 has been used to build a Lyα luminosity function (LF). The incompleteness due to objects with significant Lyα emission but a UV continuum too low for spectral extraction has been evaluated. A comparison with Hα LFs in the same redshift domain is consistent with an average Lya/Ha of ∼1 in about 15% of the star-forming galaxies. A comparison with high-redshift Lyα LFs implies an increase of the Lya luminosity density by a factor of about 16 from z ∼ 0.3 to z ∼ 3. By comparison with the factor of 5 increase in the UV luminosity density in the same redshift range, this suggests an increase of the average Lyα escape fraction with redshift.

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Deharveng JM, Small T, Barlow TA, Péroux C, Milliard B, Friedman PG et al. Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy. Astrophysical Journal. 2008 Jun 20;680(2):1072-1082. https://doi.org/10.1086/587953