We present the optical data for 195 H I-selected galaxies that fall within both the Sloan Digital Sky Survey (SDSS) and the Parkes Equatorial Survey (ES). The photometric quantities have been ...independently recomputed for our sample using a new photometric pipeline optimized for large galaxies, thus correcting for SDSS's limited reliability for automatic photometry of angularly large or low surface brightness (LSB) galaxies. We outline the magnitude of the uncertainty in the SDSS catalog-level photometry and derive a quantitative method for correcting the over-sky subtraction in the SDSS photometric pipeline. The main thrust of this paper is to present the ES/SDSS sample and discuss the methods behind the improved photometry, which will be used in future scientific analysis. We present the overall optical properties of the sample and briefly compare to a volume-limited, optically selected sample. Compared to the optically selected SDSS sample (in the similar volume), H I-selected galaxies are bluer and more luminous (fewer dwarf ellipticals and more star formation). However, compared to typical SDSS galaxy studies, which have their own selection effect, our sample is bluer, fainter, and less massive.
We utilize color information for an H I-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the H I ...selection creates a significant offset toward bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the H I selection restricts the sample to bluer, actively star-forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g - r< 0.3. We also demonstrate that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r - i colors but leave the g - r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.
Abstract
We present the results of ALMA spectroscopic follow-up of a
z
= 6.766 Ly
α
emitting galaxy behind the cluster RX J1347.1−1145. We report the detection of C
ii
158
μ
m line fully consistent ...with the Ly
α
redshift and with the peak of the optical emission. Given the magnification of
μ
= 5.0 ± 0.3, the intrinsic (corrected for lensing) luminosity of the C
ii
line is
L
C
ii
, roughly ∼5 times fainter than other detections of
z
∼ 7 galaxies. The result indicates that low
L
C
ii
in
z
∼ 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset (
) between the Ly
α
and C
ii
line is unusual, and may be indicative of ionizing photons escaping.
We present the results of ALMA spectroscopic follow-up of a z = 6.766 Ly alpha emitting galaxy behind the cluster RX J1347.1-1145. We report the detection of C II 158 mu m line fully consistent with ...the Ly alpha redshift and with the peak of the optical emission. Given the magnification of mu = 5.0 +/- 0.3, the intrinsic (corrected for lensing) luminosity of the C II line is LC II= 1.4(-0.3)(+0.3) x 10(7) L-circle dot, roughly similar to 5 times fainter than other detections of z similar to 7 galaxies. The result indicates that low LC II in z similar to 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset (Delta v = 20(-40)(+40) km s(-1)) between the Ly alpha and C II line is unusual, and may be indicative of ionizing photons escaping.
We present the results of ALMA spectroscopic follow-up of a z= 6.766 Lyalpha emitting galaxy behind the cluster RX J1347.1?1145. We report the detection of Cii 158 mu m line fully consistent with the ...Lyalpha redshift and with the peak of the optical emission. Given the magnification of mu= 5.0 + or - 0.3, the intrinsic (corrected for lensing) luminosity of the CII line is L sub(CII)= (ProQuest: Formulae and/or non-USASCII text omitted), roughlt ~5 times fainter than other detections of z~ 7 galaxies. The result indicates that low L sub(CII) in z~ 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset (Delta sub(nu)= (ProQuest: Formulae and/or non-USASCII text omitted)) between the Lyalpha and CII line is unusual, and may be indicative of ionizing photons escaping.
We present the results of ALMA spectroscopic follow-up of a z = 6.766 Ly emitting galaxy behind the cluster RX J1347.1−1145. We report the detection of C ii 158 m line fully consistent with the Ly ...redshift and with the peak of the optical emission. Given the magnification of = 5.0 0.3, the intrinsic (corrected for lensing) luminosity of the C ii line is LC ii , roughly ∼5 times fainter than other detections of z ∼ 7 galaxies. The result indicates that low LC ii in z ∼ 7 galaxies compared to the local counterparts might be caused by their low metallicities and/or feedback. The small velocity offset ( ) between the Ly and C ii line is unusual, and may be indicative of ionizing photons escaping.
We utilize color information for an H I-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the H I ...selection creates a significant offset toward bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the H I selection restricts the sample to bluer, actively star-forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g - r< 0.3. We also demonstrate that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r - i colors but leave the g - r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.
We present the optical data for 195 H I-selected galaxies that fall within both the Sloan Digital Sky Survey (SDSS) and the Parkes Equatorial Survey (ES). The photometric quantities have been ...independently recomputed for our sample using a new photometric pipeline optimized for large galaxies, thus correcting for SDSS's limited reliability for automatic photometry of angularly large or low surface brightness (LSB) galaxies. We outline the magnitude of the uncertainty in the SDSS catalog-level photometry and derive a quantitative method for correcting the over-sky subtraction in the SDSS photometric pipeline. The main thrust of this paper is to present the ES/SDSS sample and discuss the methods behind the improved photometry, which will be used in future scientific analysis. We present the overall optical properties of the sample and briefly compare to a volume-limited, optically selected sample. Compared to the optically selected SDSS sample (in the similar volume), H I-selected galaxies are bluer and more luminous (fewer dwarf ellipticals and more star formation). However, compared to typical SDSS galaxy studies, which have their own selection effect, our sample is bluer, fainter, and less massive.
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