J/A+A/643/A6    Ly{alpha}-[CII] velocity offsets in MS galaxies (Cassata+, 2020)
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The ALPINE-ALMA [CII] survey. Small Ly{alpha}-[CII] velocity offsets in
main-sequence galaxies at 4.4 < z < 6.
    Cassata P., Morselli L., Faisst A., Ginolfi M., Bethermin M., Capak P.,
    Le Fevre O., Schaerer D., Silverman J., Yan L., Lemaux B.C., Romano M.,
    Talia M., Bardelli S., Boquien M., Cimatti A., Dessauges-Zavadsky M.,
    Fudamoto Y., Fujimoto S., Giavalisco M., Hathi N.P., Ibar E., Jones G.,
    Koekemoer A.M., Mendez-Hernandez H., Mancini C., Oesch P.A., Pozzi F.,
    Riechers D.A., Rodighiero G., Vergani D., Zamorani G., Zucca E.
   <Astron. Astrophys., 643, A6 (2020)>
   =2020A&A...643A...6C    (SIMBAD/NED BibCode)
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ADC_Keywords: Surveys ; Interstellar medium ; Galaxy catalogs ; Redshifts ;
              Millimetric/submm sources ; Infrared
Keywords: galaxies: ISM - galaxies: high-redshift - submillimeter: galaxies

Abstract:
    The Lyman-{alpha} line in the ultraviolet (UV) and the [CII] line in
    the far-infrared (FIR) are widely used tools to identify galaxies in
    the early Universe and to obtain insights into interstellar medium
    (ISM) properties in high-redshift galaxies. By combining data obtained
    with ALMA in band 7 at ~320GHz as part of the ALMA Large Program to
    INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from
    DEIMOS at the Keck Observatory, VIMOS and FORS2 at the Very Large
    Telescope, we assembled a unique sample of 53 main-sequence
    star-forming galaxies at 4.4<z<6 in which we detect both the
    Lyman-{alpha} line in the UV and the [CII] line in the FIR.

    The goal of this paper is to constrain the properties of the Ly{alpha}
    emission in these galaxies in relation to other properties of the ISM.

    We used [CII], observed with ALMA, as a tracer of the systemic
    velocity of the galaxies, and we exploited the available optical
    spectroscopy to obtain the Ly{alpha}-[CII] and ISM-[CII] velocity
    offsets.

    We find that 90% of the selected objects have Ly{alpha}-[CII] velocity
    offsets in the range 0<{Delta}v_Ly{alpha}-[CII]_<400km/s, in line with
    the few measurements available so far in the early Universe, and
    significantly smaller than those observed at lower redshifts. At the
    same time, we observe ISM-[CII] offsets in the range
    -500<{Delta}v_ISM-[CII]_<0km/s, in line with values at all redshifts,
    which we interpret as evidence for outflows in these galaxies. We find
    significant anticorrelations between {Delta}v_Ly{alpha}-[CII]_ and the
    Ly{alpha} rest-frame equivalent width EW_0_(Ly{alpha}) (or
    equivalently, the Ly{alpha} escape fraction f_esc_(Ly{alpha})):
    galaxies that show smaller {Delta}v_Ly{alpha}-[CII]_ have larger
    EW_0_(Ly{alpha}) and f_esc_(Ly{alpha}).

    We interpret these results in the framework of available models for
    the radiative transfer of Ly{alpha} photons. According to the models,
    the escape of Ly{alpha} photons would be favored in galaxies with high
    outflow velocities, producing large EW_0_(Ly{alpha}) and small
    {Delta}v_Ly{alpha}-[CII]_, in agreement with our observations. The
    uniform shell model would also predict that the Ly{alpha} escape in
    galaxies with slow outflows (0<v_out_<300km/s) is mainly determined by
    the neutral hydrogen column density (NHI) along the line of sight,
    while the alternative model by Steidel et al. (2010ApJ...717..289S)
    would more highly favor a combination of NHI at the systemic velocity
    and covering fraction as driver of the Ly{alpha} escape. We suggest
    that the increase in Ly{alpha} escape that is observed in the
    literature between z~2 and z~6 is not due to a higher incidence of
    fast outflows at high redshift, but rather to a decrease in average
    NHI along the line of sight, or alternatively, a decrease in HI
    covering fraction.

Description:
    We investigate the kinematics and the physical properties of the ISM
    in a sample of 53 main-sequence star-forming galaxies at 4.4<z<6, for
    which we exploit observations of the [CII] 158uline that are
    available as part of the ALMA Large Program to INvestigate [CII] at
    Early Times (ALPINE; Cat. J/A+A/643/A2), coupled with rich
    spectroscopic and photometric data. In particular, we analyze the
    offset between the Ly{alpha} line and ISM lines with respect to the
    systemic velocity, for which [CII] can be used as proxy.

File Summary:
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 FileName      Lrecl  Records   Explanations
--------------------------------------------------------------------------------
ReadMe            80        .   This file
tableb1.dat       92       53   Properties of the sample from multiwavelength
                                 photometry
tableb2.dat       79       53   Ly{alpha}, [CII], and ISM measurements for
                                 the sample
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See also:
    J/A+A/643/A2 : ALPINE DR1 merged catalog (Bethermin+, 2020)

Byte-by-byte Description of file: tableb1.dat
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   Bytes Format Units      Label     Explanations
--------------------------------------------------------------------------------
   1- 13  A13   ---        ID        Name (G1)
  15- 19  F5.2  [Msun]     log(M)    Mass
  21- 24  F4.2  [Msun]   E_log(M)    Error on Mass (upper value)
  26- 29  F4.2  [Msun]   e_log(M)    Error on Mass (lower value)
  31- 34  F4.2 [Msun/yr]   logSFR    Star formation rate
  36- 39  F4.2 [Msun/yr] E_logSFR    Error on logSFR (upper value)
  41- 44  F4.2 [Msun/yr] e_logSFR    Error on logSFR (lower value)
  46- 49  F4.2  mag         E(B-V)   Extinction
  51- 56  F6.2  mag         MFUV     Absolute FUV magnitude
  58- 61  F4.2  mag       E_MFUV     Error on MFUV (upper value)
  63- 66  F4.2  mag       e_MFUV     Error on MFUV (lower value)
  68- 89  A22   ---         Name     Name as in ALPINE DR1 catalog
                                      (Cat. J/A+A/643/A2)
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Byte-by-byte Description of file: tableb2.dat
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   Bytes Format Units   Label       Explanations
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   1- 13  A13   ---     ID          Name (G1)
  15- 18  F4.1  ---     S/N([CII])  Signal-to-noise from [CII]
  20- 24  F5.1  0.1nm   EW0(Lya)    Ly{alpha} equivalent width
  26- 29  F4.1  0.1nm e_EW0(Lya)    rms uncertainty on EW0(Lya)
  31- 34  F4.2  ---     fesc(Lya)   Ly{alpha} escape fraction
  36- 39  F4.2  ---   E_fesc(Lya)   Error on fesc(Lya) (upper value)
  41- 44  F4.2  ---   e_fesc(Lya)   Error on fesc(Lya) (lower value)
  46- 51  F6.4  ---     z[CII]      Redshift from [CII] line
  53- 58  F6.4  ---   e_z[CII]      rms uncertainty on z[CII]
  60- 62  I3    km/s    DLya        Ly{alpha} velocity offset
  64- 66  I3    km/s  e_DLya        rms uncertainty on DLya
  68- 71  I4    km/s    DISM        ? ISM velocity offset
  73- 75  I3    km/s  E_DISM        ? Error on ISM (upper value)
  77- 79  I3    km/s  e_DISM        ? Error on ISM (lower value)
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Global notes:
Note (G1): Names starting with CG indicate objects in the CANDELS GOODS South
 area; Names starting with vc indicate objects with VUDS VIMOS/VLT spectra in
 the COSMOS field; DC indicates objects with DEIMOS spectra in the COSMOS field.
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History:
    From electronic version of the journal

References:
    Faisst et al.,  2020ApJS..247...61F,
     The ALPINE-ALMA [CII] survey: Multiwavelength ancillary data and basic
       physical measurements
    Le Fevre et al. 2020A&A...643A...1L, arXiv:1910.09517,
     The ALPINE-ALMA [CII] survey. Survey strategy, observations, and sample
     properties of 118 star-forming galaxies at 4<z<6
    Fujimoto et al. 2020ApJ...900....1F, arXiv:2003.00013
      The ALPINE-ALMA [CII] survey: Size of individual star-forming galaxies
       at z=4-6 and their extended halo structure
    Schaerer et al., 2020A&A...643A...3S
     The ALPINE-ALMA [CII] survey. Little to no evolution in the [CII]-SFR
     relation over the last 13 Gyr
    Fudamoto et al., 2020A&A...643A...4F
     The ALPINE-ALMA [CII] survey: Dust attenuation properties and obscured
     star formation at z~4.4-5.8
    Dessauges-Zavadsky et al., 2020A&A...643A...5D, arXiv:2004.10771,
     The ALPINE-ALMA [CII] survey: Molecular gas budget in the Early Universe
     as traced by [CII]
    Cassata et al., 2020A&A...643A...6C
     The ALPINE-ALMA [CII] survey. Small Lyalpha-[CII] velocity offsets in
     main-sequence galaxies at 4.4<z<6
    Ginolfi et al., 2020A&A...643A...7G, arXiv:2004.13737,
     The ALPINE-ALMA [CII] survey. Circumgalactic medium pollution and gas
     mixing by tidal stripping in a merging system at z~4.57
    Gruppioni  et al., 2020A&A...643A...8G, arXiv:2006.04974,
     The ALPINE-ALMA [CII] survey: nature, luminosity function and star
     formation history of continuum non-target galaxies up to z~6
    Khusanova et al., 2020, A&A in press, arXiv:2007.08384,
     The ALPINE-ALMA [CII] Survey: Obscured star formation rate density and
     main sequence of star-Forming galaxies at z>4
    Loiacono et al., 2020, A&A in press, arXiv:2006.04837,
     The ALPINE-ALMA [CII] survey: the luminosity function of serendipitous
     [CII] line emitters at z~5
    Yan et al, 2020ApJ...905..147Y, arXiv:2006.04835,
     The ALPINE-ALMA [CII] survey: [CII]158micron emission line luminosity
     functions at z~4-6
    Fudamoto et al., 2020, A&A in press, arXiv:2004.10760
     The ALPINE-ALMA [CII] survey: Dust attenuation properties and obscured
     star-formation at z~4.4-5.8
    Romano et al., 2020MNRAS.496..875R, arXiv:2002.00961,
     The ALPINE-ALMA [CII] survey: On the nature of an extremely obscured
     serendipitous galaxy
    Jones et al., 2020MNRAS.491L..18J, arXiv:1908.07777,
     The ALPINE-ALMA [CII] survey: A triple merger at z~4.56

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(End)                                      Patricia Vannier [CDS]    20-Jan-2021