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2061. Luminous X-ray candidates within D25 of galaxies
ID:
ivo://CDS.VizieR/J/ApJS/222/12
Title:
Luminous X-ray candidates within D25 of galaxies
Short Name:
J/ApJS/222/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using Chandra archive data we conduct a thorough survey of luminous X-ray sources. We directly analyze about 9400 ACIS Observations and cross-correlate the X-ray sources with 77000 galaxies within 250Mpc. The final catalog includes 119 unique luminous X-ray source candidates with L_X_>3x10^40^erg/s from 93 galaxies or 41 HLX candidates with L_X_>1x10^41^erg/s from 35 galaxies. We derive a moderate contamination rate due to foreground or background sources. We also cross-correlate the catalog with FIRST, perform variability and periodicity tests, and analyze one HLX candidate in particular. Our catalog could be a starting point to perform follow-up observations.
2062. LVHIS. far-infrared radio correlation
ID:
ivo://CDS.VizieR/J/MNRAS/479/3509
Title:
LVHIS. far-infrared radio correlation
Short Name:
J/MNRAS/479/3509
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we measure the far-infrared (FIR) and radio flux densities of a sample of 82 local gas-rich galaxies, including 70 "dwarf" galaxies (M_*_<10^9^M_{sun}_), from the Local Volume HI Survey (LVHIS), which is close to volume limited. It is found that LVHIS galaxies hold a tight linear FIR-radio correlation (FRC) over four orders of magnitude. However, for detected galaxies only, a trend of larger FIR-to-radio ratio with decreasing flux density is observed. We estimate the star formation rate by combining UV and mid-IR data using empirical calibration. It is confirmed that both FIR and radio emission are strongly connected with star formation but with significant non-linearity. Dwarf galaxies are found radiation deficient in both bands, when normalized by star formation rate. It urges a "conspiracy" to keep the FIR-to-radio ratio generally constant. By using partial correlation coefficient in Pearson definition, we identify the key galaxy properties associated with the FIR and radio deficiency. Some major factors, such as stellar mass surface density, will cancel out when taking the ratio between FIR and radio fluxes. The remaining factors, such as HI-to-stellar mass ratio and galaxy size, are expected to cancel each other due to the distribution of galaxies in the parameter space. Such cancellation is probably responsible for the "conspiracy" to keep the FRC alive.
2063. LVL global optical photometry
ID:
ivo://CDS.VizieR/J/MNRAS/445/881
Title:
LVL global optical photometry
Short Name:
J/MNRAS/445/881
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the global optical photometry of 246 galaxies in the Local Volume Legacy (LVL) survey. The full volume-limited sample consists of 258 nearby (D<11Mpc) galaxies whose absolute B-band magnitude span a range of -9.6<M_B_<-20.7mag. A composite optical (UBVR) data set is constructed from observed UBVR and Sloan Digital Sky Survey ugriz imaging, where the ugriz magnitudes are transformed into UBVR. We present photometry within three galaxy apertures defined at UV, optical, and IR wavelengths. Flux comparisons between these apertures reveal that the traditional optical R25 galaxy apertures do not fully encompass extended sources. Using the larger IR apertures, we find colour-colour relationships where later type spiral and irregular galaxies tend to be bluer than earlier type galaxies. These data provide the missing optical emission from which future LVL studies can construct the full panchromatic (UV-optical-IR) spectral energy distributions.
2064. LVL SEDs and physical properties
ID:
ivo://CDS.VizieR/J/MNRAS/445/899
Title:
LVL SEDs and physical properties
Short Name:
J/MNRAS/445/899
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the panchromatic spectral energy distributions (SEDs) of the Local Volume Legacy (LVL) survey which consists of 258 nearby galaxies (D<11Mpc). The wavelength coverage spans the ultraviolet to the infrared (1500{AA}-24{mu}m) which is utilized to derive global physical properties (i.e. star formation rate, stellar mass, internal extinction due to dust). With these data, we find colour-colour relationships and correlated trends between observed and physical properties (i.e. optical magnitudes and dust properties, optical colour and specific star formation rate, and ultraviolet-infrared colour and metallicity). The SEDs are binned by different galaxy properties to reveal how each property affects the observed shape of these SEDs. In addition, due to the volume-limited nature of LVL, we utilize the dwarf-dominated galaxy sample to test star formation relationships established with higher mass galaxy samples. We find good agreement with the star-forming `main-sequence' relationship, but find a systematic deviation in the infrared `main sequence' at low luminosities. This deviation is attributed to suppressed polycyclic aromatic hydrocarbon (PAH) formation in low-metallicity environments and/or the destruction of PAHs in more intense radiation fields occurring near a suggested threshold in star formation rates (sSFR) at a value of log(sSFR)~-10.2.
2065. Lya galaxies in 3 CFHTLS overdense regions
ID:
ivo://CDS.VizieR/J/ApJ/888/89
Title:
Lya galaxies in 3 CFHTLS overdense regions
Short Name:
J/ApJ/888/89
Date:
25 Oct 2021 10:16:31
Publisher:
CDS
Description:
We have carried out follow-up spectroscopy on three overdense regions of g- and r-dropout galaxies in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields, finding two new protoclusters at z=4.898 and 3.721 and a possible protocluster at z=3.834. The z=3.721 protocluster overlaps with a previously identified protocluster at z=3.675. The redshift separation between these two protoclusters is {Delta}z=0.05, which is slightly larger than the size of typical protoclusters. Therefore, if they are not the progenitors of a >10^15^M_{sun}_ halo, they would grow into closely located independent halos like a supercluster. The other protocluster at z=4.898 is also surrounded by smaller galaxy groups. These systems including protoclusters and neighboring groups are regarded as the early phase of superclusters. We quantify the spatial distribution of member galaxies of the protoclusters at z=3.675 and 3.721 by fitting triaxial ellipsoids, finding a tentative difference: one has a pancake-like shape, while the other is filamentary. This could indicate that these two protoclusters are in different stages of formation. We investigate the relation between redshift and the velocity dispersion of protoclusters, including other protoclusters from the literature, in order to compare their dynamical states. Although there is no significant systematic trend in the velocity dispersions of protoclusters with redshift, the distribution is skewed to higher velocity dispersion over the redshift range of z=2-6. This could be interpreted as two phases of cluster formation, one dominated by the steady accretion of galaxies and the other by the merging between group-size halos, perhaps depending on the surrounding large-scale environments.
2066. Ly{alpha} and OVI in galaxies around quasars
ID:
ivo://CDS.VizieR/J/ApJ/740/91
Title:
Ly{alpha} and OVI in galaxies around quasars
Short Name:
J/ApJ/740/91
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze the association of galaxies with Ly{alpha} and OVI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z_em_=0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho}=300h^-1^_72_kpc: 33/37 of our L>0.01L* galaxies show Ly{alpha} equivalent width W^Ly{alpha}^>=50 m{AA}. Galaxies of all luminosity L>0.01L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at ~10^10.5^+/-0.3M_{sun}_ for a constant N_H_=10^19^cm^-2^. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W^Ly{alpha}^>300m{AA}) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W^Ly{alpha}^=30-300m{AA} occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of ~400h^-1^_72_kpc. Regarding OVI, we observe a near unity covering fraction to {rho}=200h^-1^_72_kpc for L>0.1L* galaxies and to {rho}=300h^-1^_72_kpc for sub-L* (0.1 L*<L<L*) galaxies. Similar to our Ly{alpha} results, stronger OVI systems (W^1031^>70m{AA}) arise in the virialized halos of L>0.1L* galaxies. Unlike Ly{alpha}, the weaker OVI systems (W^1031^~30m{AA}) arise in the extended CGM of sub-L* galaxies. The majority of OVI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L~0.3L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.
2067. Ly{alpha}-[CII] velocity offsets in MS galaxies
ID:
ivo://CDS.VizieR/J/A+A/643/A6
Title:
Ly{alpha}-[CII] velocity offsets in MS galaxies
Short Name:
J/A+A/643/A6
Date:
21 Oct 2021
Publisher:
CDS
Description:
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.
2068. Ly{alpha} emission from 4<z<6 sources in COSMOS
ID:
ivo://CDS.VizieR/J/ApJ/760/128
Title:
Ly{alpha} emission from 4<z<6 sources in COSMOS
Short Name:
J/ApJ/760/128
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate spectroscopically measured Ly{alpha} equivalent widths (EWs) and escape fractions of 244 sources of which 95 are Lyman break galaxies (LBGs) and 106 Lyman alpha emitters (LAEs) at z~4.2, z~4.8, and z~5.6 selected from intermediate and narrowband observations. The sources were selected from the Cosmic Evolution Survey and observed with the DEIMOS spectrograph. We find that the distribution of EWs shows no evolution with redshift for both the LBG selected sources and the intermediate/narrowband LAEs. We also find that the Ly{alpha} escape fraction of intermediate/narrowband LAEs is on average higher and has a larger variation than the escape fraction of LBG selected sources. The escape fraction does not show a dependence with redshift. Similar to what has been found for LAEs at low redshifts, the sources with the highest extinctions show the lowest escape fractions. The range of escape fractions increases with decreasing extinction. This is evidence that the dust extinction is the most important factor affecting the escape of Ly{alpha} photons, but at low extinctions other factors, such as the H I covering fraction and gas kinematics, can be just as effective at inhibiting the escape of Ly{alpha} photons.
2069. Ly{alpha} emission-line galaxies at z=3.1
ID:
ivo://CDS.VizieR/J/ApJ/667/79
Title:
Ly{alpha} emission-line galaxies at z=3.1
Short Name:
J/ApJ/667/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe the results of an extremely deep, 0.28{deg}^2^ survey for z=3.1 Ly{alpha} emission-line galaxies in the Extended Chandra Deep Field-South. By using a narrowband 5000{AA} filter and complementary broadband photometry from the MUSYC survey, we identify a statistically complete sample of 162 galaxies with monochromatic fluxes brighter than 1.5x10^-17^ergs/cm^2^/s and observer's frame equivalent widths greater than 80{AA}
2070. Ly-alpha emitters around MRC 0316-257
ID:
ivo://CDS.VizieR/J/A+A/431/793
Title:
Ly-alpha emitters around MRC 0316-257
Short Name:
J/A+A/431/793
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observations of the radio galaxy MRC 0316-257 at z=3.13 and the surrounding field resulted in the discovery of 77 candidate Ly{alpha} emitters with a rest-frame equivalent width of >15{AA}. 31 of 40 candidate emitters observed spectroscopically have redshifts similar to that of the radio galaxy. The properties of the Ly{alpha} emission line of the 31 confirmed emitters and the radio galaxy are presented in the file table2.dat (Table 2 in the paper). The magnitudes and continuum slopes of these z~3.1 galaxies are printed in the file table4.dat (Table 4 in the paper). The Ly{alpha} galaxies are faint, blue and small, consistent with the emitters being young starforming galaxies which are still nearly dust free.