J/MNRAS/491/2057 MAGG I Near pristine gas cloud at z∼3.5 (Lofthouse+, 2020)
MUSE Analysis of Gas around Galaxies (MAGG)
I: Survey design and the environment of a near pristine gas cloud at z∼3.5.
Lofthouse E.K., Fumagalli M., Fossati M., O'Meara J.M., Murphy M.T.,
Christensen L., Prochaska J.X., Cantalupo S., Bielby R.M., Cooke R.J.,
Lusso E., Morris S.L.
<Mon. Not. R. Astron. Soc., 491, 2057-2074 (2020)>
=2020MNRAS.491.2057L 2020MNRAS.491.2057L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; QSOs ; Redshifts ; Ultraviolet ; Optical
Keywords: galaxies: evolution - galaxies: formation - galaxies: haloes -
galaxies: high-redshift - quasars: absorption lines
Abstract:
We present the design, methods, and first results of the MUSE Analysis
of Gas around Galaxies (MAGG) survey, a large programme on the
Multi-Unit Spectroscopic Explorer (MUSE) instrument at the Very Large
Telescope (VLT), which targets 28z>3.2 quasars to investigate the
connection between optically thick gas and galaxies at z∼3-4. MAGG
maps the environment of 52 strong absorption line systems at z≳3,
providing the first statistical sample of galaxies associated with
gas-rich structures in the early Universe. In this paper, we study the
galaxy population around a very metal poor gas cloud at z∼3.53 towards
the quasar J124957.23-015928.8. We detect three Lyα emitters
within ~<200km/s of the cloud redshift, at projected separations
~<185kpc (physical). The presence of star-forming galaxies near a very
metal-poor cloud indicates that metal enrichment is still spatially
inhomogeneous at this redshift. Based on its very low metallicity and
the presence of nearby galaxies, we propose that the most likely
scenario for this Lyman Limit System (LLS) is that it lies within a
filament which may be accreting on to a nearby galaxy. Taken together
with the small number of other LLSs studied with MUSE, the
observations to date show a range of different environments near
strong absorption systems. The full MAGG survey will significantly
expand this sample and enable a statistical analysis of the link
between gas and galaxies to pin down the origin of these diverse
environments at z∼3-4.
Description:
Our survey is designed to investigate the connection between optically
thick gas and galaxies at z∼3-4. For this purpose, we selected a
sample of quasars at z≳3.2 for which high-resolution (R≳30000)
spectroscopy was available from the Ultraviolet and Visual Echelle
Spectrograph (UVES; Dekker et al. 2000SPIE.4008..534D 2000SPIE.4008..534D) at VLT, the
Magellan Inamori Kyocera Echelle (MIKE; Bernstein et al.
2003SPIE.4841.1694B 2003SPIE.4841.1694B) at Magellan, and the High-Resolution Echelle
Spectrometer (HIRES; Vogt et al. 1994SPIE.2198..362V 1994SPIE.2198..362V) at Keck. This
results in a sample of quasars with magnitudes mr~<19mag. We further
restrict our sample to quasars with data at moderate or high signal to
noise (S/N≳20), and with at least one strong absorption line system
(NHI≳1017cm-2) at redshift z≳3.05. Finally, we restrict the
sample to quasars that are observable from Paranal with low airmass,
typically at declination δ<+15deg.
Our final selection comprises 28 quasars. As part of the programme ID
197.A-0384, we have observed each quasar field with five observing
blocks (OBs) of 1hr with MUSE between period 97 and period 103. After
excluding overheads, this corresponds to a total on-source observing
time of ∼4hr per field.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 83 62 Summary of the archival quasar spectroscopy
used in this survey
table3.dat 69 105 Continuum sources in the MUSE FOV extracted by
Sextractor with S/N>2 and mr<27mag
table4.dat 66 6 Line emitters extracted within 1000km/s of the
LLS at z∼3.525
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Quasar name (JHHMMSS.ss+DDMMSS.s)
21- 29 A9 --- Inst Instrument name
31- 45 A15 --- Resol Spectral resolution (range is used if
dependent on instrument arm)
47- 50 I4 0.1nm lambdamin Wavelength range covered by the spectrum
(minimum value)
52- 56 I5 0.1nm lambdamax Wavelength range covered by the spectrum
(maximum value)
58- 60 I3 --- S/Nblue S/N per pixel representative of the Lyα
forest, away from saturated absorption lines
62- 65 I4 0.1nm lambdablue Actual wavelength associated to S/Nblue
67- 69 I3 --- S/Nred ? S/N per pixel representative of the
continuum redward to the quasar Lyα
71- 74 I4 0.1nm lambdared ? Actual wavelength associated to S/Nred
76- 83 A8 km/s vdisp Nominal pixel velocity dispersion of the 1D
spectra (range is used if arm dependent)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/105] Internal object identifier
5- 27 A23 --- Name MUSE name (MUSEJHHMMSS.ss+DDMMSS.s)
29- 37 F9.5 deg RAdeg Right ascension (J2000)
39- 47 F9.6 deg DEdeg Declination (J2000)
49- 52 F4.1 mag rmag ? r-band magnitude
54- 58 F5.3 mag e_rmag ? Error on rmag
60- 67 F8.5 --- z ? Redshift obtained using MARZ
69 I1 --- q_z [1/6] Redshift confidence (1)
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Note (1): Confidence as follows:
1 = Low-S/N spectrum with no clearly identifiable features, which can yield
a confident redshift measurement
2 = Single emission line with low-S/N continuum and weak or no other
identifiable lines, for which the redshift is uncertain
3 = One strong emission or absorption line with some additional low-S/N
emission or absorption features for which we can determine a confident
redshift
4 = Multiple high-S/N emission or absorption lines, which yield an accurate
redshift
6 = Star
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1 I1 --- ID [1/6] Inernal object identifier
3- 4 I2 h RAh Right ascension (J2000)
6- 7 I2 min RAm Right ascension (J2000)
9- 14 F6.3 s RAs Right ascension (J2000)
16 A1 --- DE- Declination sign (J2000)
17- 18 I2 deg DEd Declination (J2000)
20- 21 I2 arcmin DEm Declination (J2000)
23- 27 F5.2 arcsec DEs Declination (J2000)
29- 32 F4.1 10-21W/m2 Fline Line flux
34- 36 F3.1 10-21W/m2 e_Fline Error on Fline
38- 41 F4.1 10+34W Lline Line luminosity
43- 45 F3.1 10+34W e_Lline Error on Lline
47- 51 F5.2 --- ISN Integrated S/N of the source
53 I1 --- Class [1/2] Confidence class based on ISN (1)
55- 61 F7.5 --- z Redshift
63- 66 I4 km/s voff Velocity offset relative to the central
component of the LLS
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Note (1): Class as follows:
1 = The first class contains sources with an ISN>7 and consists of our
highest purity sample, at the expense of a lower completeness
2 = The second class includes sources with an ISN>5, extending the
completeness at the expense of the purity
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 14-Feb-2023