- ID:
- ivo://CDS.VizieR/J/ApJ/847/38
- Title:
- Extreme emission line galaxies at z<~0.05
- Short Name:
- J/ApJ/847/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Searching for extreme emission line galaxies allows us to find low-mass metal-poor galaxies that are good analogs of high redshift Ly{alpha} emitting galaxies. These low-mass extreme emission line galaxies are also potential Lyman-continuum leakers. Finding them at very low redshifts (z<~0.05) allows us to be sensitive to even lower stellar masses and metallicities. We report on a sample of extreme emission line galaxies at z<~0.05 (blueberry galaxies). We selected them from SDSS broadband images on the basis of their broadband colors and studied their properties with MMT spectroscopy. From the entire SDSS DR12 photometric catalog, we found 51 photometric candidates. We spectroscopically confirm 40 as blueberry galaxies. These blueberries are dwarf starburst galaxies with very small sizes (<1kpc) and very high ionization ([OIII]/[OII]~10-60). They also have some of the lowest stellar masses (log(M/M_{sun}_)~6.5-7.5) and lowest metallicities (7.1<12+log(O/H)<7.8) of starburst galaxies. Thus, they are small counterparts to green pea galaxies and high redshift Ly{alpha} emitting galaxies.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/742/111
- Title:
- Extreme emission-line galaxies in CANDELS
- Short Name:
- J/ApJ/742/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify an abundant population of extreme emission-line galaxies (EELGs) at redshift z~1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). Sixty-nine EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broadband magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines - with rest-frame equivalent widths ~1000{AA} - in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with ~10^8^M_{sun}_ in stellar mass, undergoing an enormous starburst phase with M_*_/(dM/dt)_*_ of only ~15Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the comoving number density (3.7x10^-4^Mpc^-3^) can produce in ~4Gyr much of the stellar mass density that is presently contained in 10^8^-10^9^M_{sun}_ dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z>1.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/347
- Title:
- Extremely Isolated Galaxies. II.
- Short Name:
- J/MNRAS/469/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected a sample of 41 extremely isolated galaxies (EIGs) from the local Universe using both optical and HI Arecibo Legacy Fast ALFA survey redshifts. Narrow-band H{alpha} and wide-band imaging along with public data were used to derive star formation rates (SFRs), star formation histories and morphological classifications for the EIGs. We have found that the extreme isolation of the EIGs does not affect considerably their star formation compared to field galaxies. EIGs are typically 'blue cloud' galaxies that fit the 'main sequence of star-forming galaxies' and may show asymmetric star formation and strong compact star-forming regions. We discovered surprising environmental dependences of the HI content, M_HI_, and of the morphological type of EIGs; the most isolated galaxies (of subsample EIG-1) have lower M_HI_ on average (with 2.5{sigma} confidence) and a higher tendency to be early types (with 0.94 confidence) compared to the less isolated galaxies of subsample EIG-2. To the best of our knowledge, this is the first study that finds an effect in which an isolated sample shows a higher fraction of early types compared to a less isolated sample. Both early-type and late-type EIGs follow the same colour-to-M_*_, SFR-to-M_*_ (main sequence) and M_HI_-to-M_*_ relations. This indicates that the mechanisms and factors governing star formation, colour and the M_HI_-to-M_*_ relation are similar in early-type and late-type EIGs, and that the morphological type of EIGs is not governed by their M_HI_ content, colour or SFR.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/110
- Title:
- Extremely metal-poor galaxies in SDSS. II.
- Short Name:
- J/ApJ/819/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extremely metal-poor (XMP) galaxies are defined to have a gas-phase metallicity smaller than a tenth of the solar value (12+log[O/H]<7.69). They are uncommon, chemically and possibly dynamically primitive, with physical conditions characteristic of earlier phases of the universe. We search for new XMPs in the Sloan Digital Sky Survey (SDSS) in a work that complements Paper I (Morales-Luis+, 2011, J/ApJ/743/77). This time, high electron temperature objects are selected; metals are a main coolant of the gas, so metal-poor objects contain high-temperature gas. Using the algorithm k-means, we classify 788677 spectra to select 1281 galaxies that have particularly intense [OIII]{lambda}4363 with respect to [OIII]{lambda}5007, which is a proxy for high electron temperature. The metallicity of these candidates was computed using a hybrid technique consistent with the direct method, rendering 196 XMPs. A less restrictive noise constraint provides a larger set with 332 candidates. Both lists are provided in electronic format. The selected XMP sample has a mean stellar mass around 10^8^M_{sun}_, with the dust mass ~10^3^M_{sun}_ for typical star-forming regions. In agreement with previous findings, XMPs show a tendency to be tadpole-like or cometary. Their underlying stellar continuum corresponds to a fairly young stellar population (<1Gyr), although young and aged stellar populations coexist at the low-metallicity starbursts. About 10% of the XMPs show large N/O. Based on their location in constrained cosmological numerical simulations, XMPs have a strong tendency to appear in voids and to avoid galaxy clusters. The puzzling 2%-solar low-metallicity threshold exhibited by XMPs remains.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/77
- Title:
- Extremely metal-poor (XMP) galaxies in SDSS
- Short Name:
- J/ApJ/743/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carry out a systematic search for extremely metal-poor (XMP) galaxies in the spectroscopic sample of Sloan Digital Sky Survey (SDSS) data release 7 (DR7). The XMP candidates are found by classifying all the galaxies according to the form of their spectra in a region 80{AA} wide around H{alpha}. Due to the data size, the method requires an automatic classification algorithm. We use k-means. Our systematic search renders 32 galaxies having negligible [NII] lines, as expected in XMP galaxy spectra. Twenty-one of them have been previously identified as XMP galaxies in the literature - the remaining 11 are new. This was established after a thorough bibliographic search that yielded only some 130 galaxies known to have an oxygen metallicity 10 times smaller than the Sun (explicitly, with 12+log(O/H)<=7.65). XMP galaxies are rare; they represent 0.01% of the galaxies with emission lines in SDSS/DR7. Although the final metallicity estimate of all candidates remains pending, strong-line empirical calibrations indicate a metallicity about one-tenth solar, with the oxygen metallicity of the 21 known targets being 12+log(O/H)~7.61+/-0.19. Since the SDSS catalog is limited in apparent magnitude, we have been able to estimate the volume number density of XMP galaxies in the local universe, which turns out to be (1.32+/-0.23)x10^-4^Mpc^-3^. The XMP galaxies constitute 0.1% of the galaxies in the local volume, or ~0.2% considering only emission-line galaxies. All but four of our candidates are blue compact dwarf galaxies, and 24 of them have either cometary shape or are formed by chained knots.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/83
- Title:
- 22 extreme [OIII] emitters at z~0.5 from SDSS-DR14
- Short Name:
- J/ApJ/860/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have found a sample of extreme emission-line galaxies (EELGs) with strong [OIII]{lambda}5007 emission at z~0.5. Using broadband photometric selection and requiring small uncertainties in photometry, we searched the 14th Data Release of the Sloan Digital Sky Survey (SDSS) and found 2658 candidates with strong i-band excess (i-z<=r-i-0.7). We further obtained 649 SDSS spectra of these objects, and visually identified 22 [OIII] emitters lying at 0.40<z<0.63. Having constructed their ultraviolet-infrared spectral energy distributions, we found that they have fairly blue r-W2 and red W1-W4 colors, indicative of strong, warm dust emission. Their rest-frame [OIII]{lambda}5007 equivalent widths are mostly 200-600{AA}, and their high [OIII]{lambda}5007/H{beta} ratios put them at the boundary of star-forming galaxies and active galactic nuclei on line ratio classification diagrams. The typical E(B-V) and electron temperature of [OIII] emitters are ~0.1-0.3mag and ~104K, respectively. The lowest metallicity of our [OIII] emitters with S/N[OIII]{lambda}4363>3 is 12+log(O/H)=7.98_-0.02_^+0.12^, with a median value of 8.24_-0.04_^+0.05^. Our [OIII] emitters exhibit remarkably high line luminosity-18/22 have L[OIII]{lambda}5007>5x10^42^erg/s and 5/22 have L[OIII]{lambda}5007>10^43^erg/s. Their estimated volume number density at z~0.5 is ~2x10^-8^Mpc^-3^, with L[OIII]{lambda}5007 down to ~3x10^42^erg/s. The cumulative number distribution of EELGs across different redshifts is indicative of a strong redshift evolution at the bright end of the [OIII] luminosity function.
- ID:
- ivo://archive.stsci.edu/euve
- Title:
- Extreme Ultraviolet Explorer
- Short Name:
- EUVE
- Date:
- 22 Jul 2020 21:28:51
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- Launched in June, 1992, The Extreme Ultraviolet Explorer (EUVE) conducted the first extreme ultraviolet (70-760 Angstroms) survey of the sky and subsequently began a Guest Observer Program of pointed
- ID:
- ivo://CDS.VizieR/J/ApJS/153/119
- Title:
- Faint blue objects at high galactic latitude
- Short Name:
- J/ApJS/153/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The US (UV-excess Starlike) survey has cataloged 3987 objects in 7 high Galactic latitude fields according to their optical colors, magnitudes, and morphologies using photographic techniques. This paper analyzes the effectiveness of the survey at producing finding lists for complete samples of hot stars and quasars that exhibit blue and/or ultraviolet excess (B-UVX) relative to the colors of halo F and G subdwarf stars. A table of 599 spectroscopic identifications summarizes the spectroscopic coverage of the US objects that has been accomplished to date.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2074
- Title:
- Faint Chandra sources in SWIRE
- Short Name:
- J/AJ/129/2074
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We exploit deep combined observations with Spitzer and Chandra of the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) in the ELAIS N1 region to investigate the nature of the faint X-ray and IR sources in common, to identify active galactic nucleus (AGN)/starburst diagnostics, and to study the sources of the X-ray and IR cosmic backgrounds (XRB and CIRB).
- ID:
- ivo://CDS.VizieR/J/AJ/130/1324
- Title:
- Faint emission-line galaxies at z<=1.6
- Short Name:
- J/AJ/130/1324
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Grism Parallel Survey, a large program obtaining deep, slitless ACS grism (R~100) spectroscopy of high-latitude HST parallel fields. We identify 601 compact emission-line galaxies at z<=1.6, reaching emission lines to a flux limit of >~5x10^-18^ergs/cm^2^/s (3{sigma}). We determine redshifts by cross-correlation of the target spectra with template spectra, followed by visual inspection. We measure star formation rates from the observed [OII]{lambda}3727, [OIII]{lambda}5007, and H{alpha} line fluxes.
