Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSDSS-IV MaNGA: The Nature of an Off-galaxy H$alpha$ Blob -- A Multi-wavelength View of Offset Cooling in a Merging Galaxy Group
71
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Galaxies in dense environments, such as groups and clusters, experience various processes by which galaxies gain and lose gas. Using data from the SDSS-IV MaNGA survey, we previously reported the discovery of a giant (6 -- 8 kpc in diameter) H$alpha$ blob, Totoro, about 8 kpc away from a pair of galaxies (Satsuki and Mei) residing in a galaxy group which is experiencing a group-group merger. Here, we combine interferometric $^{12}$CO(1--0) molecular gas data, new wide-field H$alpha$, $u$-band data, and published X-ray data to determine the origin of the blob. Several scenarios are discussed to account for its multi-wavelength properties, including (1) H$alpha$ gas being stripped from galaxy Satsuki by ram-pressure; (2) a separated low-surface-brightness galaxy; (3) gas being ejected or ionized by an active galactic nucleus (AGN); and (4) a cooling intra-group medium (IGM). Scenarios (1) and (2) are less favored by the present data. Scenario (3) is also less likely as there is no evidence for an active ongoing AGN in the host galaxy. We find that the CO (cold) and H$alpha$ (warm) gas coexist with X-ray (hot) structures; moreover, the derived cooling time is within the regime where molecular and H$alpha$ gas are expected. The coexistence of gas with different temperatures also agrees with that of cooling gas in other systems. Our multi-wavelength results strongly suggest that the CO and H$alpha$ gas are the product of cooling from the IGM at its current location, i.e., cooling has occurred, and may be ongoing, well outside the host-galaxy core.
rate research
Read More
H$alpha$ blobs are off-galaxy emission-line regions with weak or no optical counterparts. They are mostly visible in H$alpha$ line, appearing as concentrated blobs. Such unusual objects have been rarely observed and studied, and their physical origin is still unclear. We have identified 13 H$alpha$ blobs in the public data of MaNGA survey, by visually inspecting both the SDSS optical images and the spatially resolved maps of H$alpha$ line for $sim 4600$ galaxy systems. Among the 13 H$alpha$ blobs, 2 were reported in previously MaNGA-based studies and 11 are newly discovered. This sample, though still small in size, is by far the largest sample with both deep imaging and integral field spectroscopy. Therefore, for the first time we are able to perform statistical studies to investigate the physical origin of H$alpha$ blobs. We examine the physical properties of these H$alpha$ blobs and their associated galaxies, including their morphology, environments, gas-phase metallicity, kinematics of ionized gas, and ionizing sources. We find that the H$alpha$ blobs in our sample can be broadly divided into two groups. One is associated with interacting/merging galaxy systems, of which the ionization is dominated by shocks or diffuse ionized gas. It is likely that these H$alpha$ blobs used to be part of their nearby galaxies, but were stripped away at some point due to tidal interactions. The other group is found in gas-rich systems, appearing as low-metallicity star-forming regions that are visually detached from the main galaxy.
We report the discovery of a mysterious giant $H_{alpha}$ blob that is $sim 8$ kpc away from the main MaNGA target 1-24145, one component of a dry galaxy merger, identified in the first-year SDSS-IV MaNGA data. The size of the $H_{alpha}$ blob is $sim$ 3-4 kpc in radius, and the $H_{alpha}$ distribution is centrally concentrated. However, there is no optical continuum counterpart in deep broadband images reaching $sim$26.9 mag arcsec$^{-2}$ in surface brightness. We estimate that the masses of ionized and cold gases are $3.3 times 10^{5}$ $rm M_{odot}$ and $< 1.3 times 10^{9}$ $rm M_{odot}$, respectively. The emission-line ratios indicate that the $H_{alpha}$ blob is photoionized by a combination of massive young stars and AGN. Furthermore, the ionization line ratio decreases from MaNGA 1-24145 to the $H_{alpha}$ blob, suggesting that the primary ionizing source may come from MaNGA 1-24145, likely a low-activity AGN. Possible explanations of this $H_{alpha}$ blob include AGN outflow, the gas remnant being tidally or ram-pressure stripped from MaNGA 1-24145, or an extremely low surface brightness (LSB) galaxy. However, the stripping scenario is less favoured according to galaxy merger simulations and the morphology of the $H_{alpha}$ blob. With the current data, we can not distinguish whether this $H_{alpha}$ blob is ejected gas due to a past AGN outburst, or a special category of `ultra-diffuse galaxy (UDG) interacting with MaNGA 1-24145 that further induces the gas inflow to fuel the AGN in MaNGA 1-24145.
We study the internal radial gradients of stellar population properties within $1.5;R_{rm e}$ and analyse the impact of galaxy environment. We use a representative sample of 721 galaxies with masses ranging between $10^{9};M_{odot}$ to $10^{11.5};M_{odot}$ from the SDSS-IV survey MaNGA. We split this sample by morphology into early-type and late-type galaxies. Using the full spectral fitting code FIREFLY, we derive the light and mass-weighted stellar population properties age and metallicity, and calculate the gradients of these properties. We use three independent methods to quantify galaxy environment, namely the $N^{th}$ nearest neighbour, the tidal strength parameter $Q$ and distinguish between central and satellite galaxies. In our analysis, we find that early-type galaxies generally exhibit shallow light-weighted age gradients in agreement with the literature and mass-weighted median age gradients tend to be slightly positive. Late-type galaxies, instead, have negative light-weighted age gradients. We detect negative metallicity gradients in both early and late-type galaxies that correlate with galaxy mass, with the gradients being steeper and the correlation with mass being stronger in late-types. We find, however, that stellar population gradients, for both morphological classifications, have no significant correlation with galaxy environment for all three characterisations of environment. Our results suggest that galaxy mass is the main driver of stellar population gradients in both early and late-type galaxies, and any environmental dependence, if present at all, must be very subtle.
We present the results of the archaeological analysis of the stellar populations of a sample of ~4,000 galaxies observed by the SDSS-IV-MaNGA survey using Pipe3D. Based on this analysis we extract a sample of ~150,000 SFRs and stellar masses that mimic a single cosmological survey covering the redshift range between z~0 to z~7. We confirm that the Star-Forming Main Sequence holds as a tight relation in this range of redshifts, and evolves strongly in both the zero-point and slope. This evolution is different for the population of local star-forming (SFGs) and retired (RGs) galaxies, with the latter presenting a stronger evolution in the zero-point and a weaker evolution in the slope. The fraction of RGs decreases rapidly with z, particularly for those classified as RGs at z~0. Contrary to previous studies we detect RGs well above z>1, although not all of them are progenitors of local RGs. Finally, adopting the required corrections to make the survey complete in mass in a limited volume, we recover the cosmic star-formation rate (SFR), stellar mass density, and average specific SFR histories of the Universe in this wide range of look-back times, with a remarkable agreement with the values reported by various cosmological surveys. We demonstrate that the progenitors of local RGs were more actively forming stars in the past, contributing to most of the cosmic SFR density at z>0.5, and to most of the cosmic stellar mass density at any redshift. They suffer a general quenching in the SFR at z~0.35. Below this redshift the progenitors of local SFGs dominate the SFR density of the Universe.
Chemical abundance determinations in Low-Ionization Nuclear Line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies (MaNGA) survey was employed to derive the O/H abundance of the UGC4805 nucleus based on the extrapolation of the disk abundance gradient, on calibrations between O/H abundance and strong emission-lines for Active Galactic Nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-Asymptotic Giant Branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN and p-AGB photoionization models produce similar O/H values for the UGC4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC4805 nucleus probably has a stellar origin rather than an AGN.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
