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Register a new userFour newly discovered HII galaxies
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We present the results of spectroscopy campaigns for planetary nebula candidates, where we have identified four objects as Seyfert galaxies. All observations have been carried out by a group of French amateur astronomers. During the campaigns at the Cote dAzur observatory at Calern (France), four HII galaxies could be identified. Using the naming convention of our campaign, these objects are (1) App 1 (RA: 22h 49m 20.23s, DEC: +46{deg}07{arcmin}37.17{arcsec}), (2) Pre 21 (RA: 18h 04m 19.62s, DEC: +00{deg}08{arcmin}04.96{arcsec}), (3) Pre 24 (RA: 04h 25m 53.63s, DEC: +39{deg}49{arcmin}19.69{arcsec}), and (4) Ra 69 (RA: 19h 30m 23.64s, DEC: +37{deg}37{arcmin}06.58{arcsec}).
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We present the photometric properties of 2210 newly identified dwarf galaxy candidates in the MATLAS fields. The Mass Assembly of early Type gaLAxies with their fine Structures (MATLAS) deep imaging survey mapped $sim$142 deg$^2$ of the sky around nearby isolated early type galaxies using MegaCam on the Canada-France-Hawaii Telescope, reaching surface brightnesses of $sim$ 28.5 - 29 in the g-band. The dwarf candidates were identified through a direct visual inspection of the images and by visually cleaning a sample selected using a partially automated approach, and were morphologically classified at the time of identification. Approximately 75% of our candidates are dEs, indicating that a large number of early type dwarfs also populate low density environments, and 23.2% are nucleated. Distances were determined for 13.5% of our sample using pre-existing $z_{spec}$ measurements and HI detections. We confirm the dwarf nature for 99% of this sub-sample based on a magnitude cut $M_g$ = -18. Additionally, most of these ($sim$90%) have relative velocities suggesting that they form a satellite population around nearby massive galaxies rather than an isolated field sample. Assuming that the candidates over the whole survey are satellites of the nearby galaxies, we demonstrate that the MATLAS dwarfs follow the same scaling relations as dwarfs in the Local Group as well as the Virgo and Fornax clusters. We also find that the nucleated fraction increases with $M_g$, and find evidence of a morphology-density relation for dwarfs around isolated massive galaxies.
We have recently reported the discovery of five low redshift Lyman continuum (LyC) emitters (LCEs, hereafter) with absolute escape fractions fesc(LyC) ranging from 6 to 13%, higher than previously found, and which more than doubles the number of low redshift LCEs.We use these observations to test theoretical predictions about a link between the characteristics of the Lyman-alpha (Lya) line from galaxies and the escape of ionising photons. We analyse the Lya spectra of eight LCEs of the local Universe observed with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (our five leakers and three galaxies from the litterature), and compare their strengths and shapes to the theoretical criteria and comparison samples of local galaxies: the Lyman Alpha Reference Survey, Lyman Break Analogs, Green Peas, and the high-redshift strong LyC leaker Ion2. Our LCEs are found to be strong Lya emitters, with high equivalent widths, EW(Lya)> 70 {AA}, and large Lya escape fractions, fesc(Lya) > 20%. The Lya profiles are all double-peaked with a small peak separation, in agreement with our theoretical expectations. They also have no underlying absorption at the Lya position. All these characteristics are very different from the Lya properties of typical star-forming galaxies of the local Universe. A subset of the comparison samples (2-3 Green Pea galaxies) share these extreme values, indicating that they could also be leaking. We also find a strong correlation between the star formation rate surface density and the escape fraction of ionising photons, indicating that the compactness of star-forming regions plays a role in shaping low column density paths in the interstellar medium of LCEs. The Lya properties of LCEs are peculiar: Lya can be used as a reliable tracer of LyC escape from galaxies, in complement to other indirect diagnostics proposed in the literature.
We report the results of an expanded search for z~9-10 candidates over the ~883 arcmin^2 CANDELS+ERS fields. This study adds 147 arcmin^2 to the search area we consider over the CANDELS COSMOS, UDS, and EGS fields, while expanding our selection to include sources with bluer J_{125}-H_{160} colors than our previous J_{125}-H_{160}>0.5 mag selection. In searching for new z~9-10 candidates, we make full use of all available HST, Spitzer/IRAC, and ground-based imaging data. As a result of our expanded search and use of broader color criteria, 3 new candidate z~9-10 galaxies are identified. We also find again the z=8.683 source previously confirmed by Zitrin+2015. This brings our sample of probable z~9-11 galaxy candidates over the CANDELS+ERS fields to 19 sources in total, equivalent to 1 candidate per 47 arcmin^2 (1 per 10 WFC3/IR fields). To be comprehensive, we also discuss 28 mostly lower likelihood z~9-10 candidates, including some sources that seem to be reliably at z>8 using the HST+IRAC data alone, but which the ground-based data show are much more likely at z<4. One case example is a bright z~9.4 candidate COS910-8 which seems instead to be at z~2. Based on this expanded sample, we obtain a more robust LF at z~9 and improved constraints on the volume density of bright z~9 and z~10 galaxies. Our improved z~9-10 results again reinforce previous findings for strong evolution in the UV LF at z>8, with a factor of ~10 evolution seen in the luminosity density from z~10 to z~8.
To understand the nature of transient obscuring outflows in active galactic nuclei, we observed the Seyfert 1 galaxy NGC 3783 on two occasions in December 2016 triggered by Swift monitoring indicating strong soft X-ray absorption in November. We obtained ultraviolet spectra using COS on HST and optical spectra using FEROS on the MPG/ESO 2.2-m telescope that were simultaneous with X-ray spectra from XMM-Newton and NuSTAR. We find new components of broad, blue-shifted absorption associated with Ly$alpha$, ion{N}{v}, ion{Si}{iv}, and ion{C}{iv} in our COS spectra. The absorption extends from velocities near zero in the rest-frame of the host galaxy to $-6200$ $rm km~s^{-1}$. These features appear for the first time in NGC 3783 at the same time as the heavy soft X-ray absorption seen in the XMM-Newton X-ray spectra. The X-ray absorption has a column density of $sim 10^{23}~rm cm^{-2}$, and it partially covers the X-ray continuum source. The X-ray absorption becomes more transparent in the second observation, as does the UV absorption. Combining the X-ray column densities with the UV spectral observations yields an ionization parameter for the obscuring gas of log $xi =1.84^{+0.4}_{-0.2}$ $rm erg~cm~s^{-1}$. Despite the high intensity of the UV continuum in NGC 3783, F(1470 AA)=$8 times 10^{-14}~rm erg~cm^{-2}~s^{-1}~AA^{-1}$, the well known narrow UV absorption lines are deeper than in earlier observations in unobscured states, and low ionization species such as ion{C}{iii} appear, indicating that the narrow-line gas is more distant from the nucleus and is being shadowed by the gas producing the obscuration. Despite the high continuum flux levels in our observations of NGC 3783, moderate velocities in the UV broad line profiles have substantially diminished. We suggest that a collapse of the broad line region has led to the outburst and triggered the obscuring event.
The work on the kinematical parameters and spatial shape structure have been performed with Gaia DR2 astrometry data of the new recently southern discovered open clusters; UFMG 1, UFMG 2, and UFMG 3 in the vicinity (1.3 degrees radius) of the rarely studied NGC 5999. The apexes positions with AD-diagram method are computed for about 107, 168, 98, and 154 members of these star clusters, respectively, our calculated values of apex coordinates, seems like: (A, D) = (102.40 +/- 1.02 & -4.60 +/- 0.47; NGC 5999), (96.69 +/- 1.10 & -0.58 +/- 0.045; UFMG 1), (97.47 +/- 1.09 & 1.56 +/- 0.051; UFMG 2), and (98.65 +/- 1.12 & -0.26 +/- 0.060; UFMG 3). On the other hand, Velocity Ellipsoid Parameters VEPs for those are also computed; e.g. space velocities due to Galactic coordinates, dispersion velocities (sigma_1, sigma_2, sigma_3) due to matrix elements for all ij, projected distances (X_sun, Y_sun, Z_sun) on the plane disc, and the Solar elements (S_sun, l_A, b_A). According to an approximation of spatial and kinematical shape, UFMGs and NGC 5999 seem to have a spatial difference in their space locations but they appear to have formed in the same region of the Galactic disc. The total cumulative mass MC; including total number of main-sequence NMS and non-main-sequence Nnon-MS of these clusters also evaluated here with a second-order polynomial of mass-luminosity relation in order to get clusters tidal radii (pc). Finally, we concluded that NGC 5999, UFMG 1, and UFMG 2 are dynamically relaxed (i.e. tau >> 1), and the fourth one in non-relaxed.
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